Valine and nonessential amino acids affect bidirectional transport rates of leucine and isoleucine in bovine mammary epithelial cells

A more complete understanding of the mechanisms controlling AA transport in mammary glands of dairy cattle will help identify solutions to increase nitrogen feeding efficiency on farms. It was hypothesized that Ala, Gln, and Gly (NEAAG), which are actively transported into cells and exchanged for all branched-chain AA (BCAA), may stimulate transport of BCAA, and that Val may antagonize transport of the other BCAA due to transporter competition. Thus, we evaluated the effects of varying concentrations of NEAAG and Val on transport and metabolism of the BCAA Ala, Met, Phe, and Thr by bovine mammary epithelial cells. Primary cultures of bovine mammary epithelial cells were assigned to treatments of low (70% of mean in vivo plasma concentrations of lactating dairy cows) and high (200%) concentrations of Val and NEAAG (LVal and LNEAAG, HVal and HNEAAG, respectively) in a 2 × 2 factorial design. Cells were preloaded with treatment media containing [15N]-labeled AA for 24 h. The [15N]-labeled media were replaced with treatment media containing [13C]-labeled AA. Media and cells were harvested from plates at 0, 0.5, 1, 5, 15, 30, 60, and 240 min after application of the [13C]-labeled AA and assessed for [15N]- and [13C]-AA label concentrations. The data were used to derive transport, transamination, irreversible loss, and protein-synthesis fluxes. All Val fluxes, except synthesis of rapidly exchanging tissue protein, increased with the HVal treatment. Interestingly, the rapidly exchanging tissue protein, transamination, and irreversible-loss rate constants decreased with HVal, indicating that the significant flux increases were primarily driven by mass action with the cells resisting the flux increases by downregulating activity. However, the decreases could also reflect saturation of processes that would drive down the mass-action rate constants. This is supported by decreases in the same rate constants for Ile and Leu with HVal. This could be due to either competition for shared transamination and oxidation reactions or a reduction in enzymatic activity. Also, NEAAG did not affect Val fluxes, but influx and efflux rate constants increased for both Val and Leu with HNEAAG, indicating an activating substrate effect. Overall, AA transport rates generally responded concordantly with extracellular concentrations, indicating the transporters are not substrate-saturated within the in vivo range. However, BCAA transamination and oxidation enzymes may be approaching saturation within in vivo ranges. In addition, System L transport activity appeared to be stimulated by as much as 75% with high intracellular concentrations of Ala, Gln, and Gly. High concentrations of Val antagonized transport activity of Ile and Leu by 68% and 15%, respectively, indicating competitive inhibition, but this was only observable at HNEAAG concentrations. The exchange transporters of System L transport 8 of the essential AA that make up approximately 40% of milk protein, so better understanding this transporter is an important step for increased efficiency.

Measuring bioavailability, utilization, and excretion of rumen-protected lysine in lactating cows using an isotope technique

Supplementing a diet with rumen-protected amino acids (AAs) is a common feeding strategy for efficient production. For a cost-effective use of rumen-protected AA, the accurate bioavailability of rumen-protected amino acids should be known and their metabolism after absorption needs to be well understood. The current study determined the bioavailability, absorption, utilization, and excretion of rumen-protected Lys (RP-Lys). Four ruminally cannulated cows in a 4 × 4 Latin square design (12 d for diet adaptation; 5 or 6 d for total collections) received the following treatments: L0, a basal diet; L25, the basal diet and L-Lys infused into the abomasum to provide 25.9 g/d L-Lys; L50, the basal diet and L-Lys infused into the abomasum to provide 51.8 g/d L-Lys; and RPL, the basal diet supplemented with 105 g/d (as-is) of RP-Lys to provide 26.7 g of digestible Lys. During the last 5 or 6 d in each period, 15N-Lys (0.38 g/d) was infused into the abomasum for all cows to label the pool of AA, and the total collection of milk, urine, and feces were conducted. 15N enrichment of samples on d 4 and 5 were used to calculate the bioavailability and Lys metabolism. We used a model containing a fast AA turnover (≤ 5 d) and slow AA turnover pool (> 5 d) to calculate fluxes of Lys. The Lys flux to the fast AA turnover pool (absorbed Lys + Lys from the slow AA turnover pool to fast AA turnover pool) was calculated using 15N enrichment of milk Lys. The flux of Lys from the fast AA turnover pool to milk and urine was calculated using 15N transfer into milk and urine. Then, absorbed Lys was estimated by the sum of Lys flux to milk and urine assuming no net utilization of Lys by body tissues. Duodenal Lys flow was estimated by 15N enrichment of fecal Lys. The bioavailability of RP-Lys was calculated from duodenal Lys flows and Lys absorption for RPL. Increasing Lys supply from L25 to L50 increased Lys utilization for milk by 9 g/d but also increased urinary excretion by 10 g/d. For RPL, absorbed Lys was estimated to be 136 g/d where 28 g of absorbed Lys originated from RP-Lys. In conclusion, 68% of bioavailability was obtained for RP-Lys. The Lys provided from RP-Lys was not only utilized for milk protein (48%) but also excreted in urine (20%) after oxidation.

Hydroponic barley supplementation fed with high protein diets improves the production performance of lactating dairy cows

The study investigated the effects of dietary protein level and the inclusion of hydroponic barley sprouts (HB) on lactation performance, blood biochemistry and N use efficiency in mid-lactation dairy cows. Treatments were arranged in a 2 × 2 factorial design with 2 crude protein (CP) levels [16.8% and 15.5% of dry matter (DM)], with HB (4.8% of DM, replacing 4.3% of alfalfa hay and 0.5% of distillers dried grains with solubles (DDGS)) or without HB. Forty-eight multiparous Holstein dairy cows (146 ± 15 d in milk, 40 ± 5 kg/d of milk) were randomly allocated to 1 of 4 diets: high protein diet (16.8% CP, HP), HP with HB (HP+HB), low protein diet (15.5% CP, LP), or LP with HB (LP+HB). An interaction between CP × HB on dry matter intake (DMI) was detected, with DMI being unaffected by HB inclusion in cows fed the high CP diets, but was lower in cows fed HB when the low CP diet was fed. A CP × HB interaction was also observed on milk and milk protein yield, which was higher in cows fed HB with HP, but not LP. Inclusion of HB also tended to reduce milk fat content, and feeding HP resulted in a higher milk protein and milk urea N content, but lower milk lactose content. Feed efficiency was increased by feeding HP or HB diets, whereas N efficiency was higher for cows fed LP or HB diets. There was an interaction on the apparent total-tract digestibility of DM and CP, which was higher when HB was fed along with HP, but reduced when fed with LP, whereas the digestibility of ADF was increased by feeding low protein diets. In conclusion, feeding a low protein diet had no adverse effect on cow performance, while feeding HB improved milk and milk component yield, and N efficiency when fed with a high CP diet, but compromised cow performance with a low CP diet.

Reducing dietary protein and supplementation with starch or rumen-protected methionine and its effect on performance and nitrogen efficiency in dairy cows fed a red clover and grass silage-based diet

The increasing cost of milk production, in association with tighter manure N application regulations and challenges associated with ammonia emissions in many countries has increased interest in feeding lower crude protein (CP) diets based on legume silages. Most studies have focused on alfalfa silage, and there is a lack of information on low CP diets based on red clover silage. Our objectives were to examine the effects of dietary CP content and supplementing a low CP diet with dietary starch or rumen-protected Met (RPMet) on the performance, metabolism, and nitrogen-use-efficiency (NUE; milk N output/N intake) in dairy cows fed a red clover and grass silage-based diet. Fifty-six Holstein-Friesian dairy cows were blocked and randomly allocated to 1 of 4 diets over a 14-week feeding period. Diets were based on red clover and grass silages at a ratio of 50:50 (dry matter (DM) basis) and were fed as a total mixed ration, with a forage-to-concentrate ratio of 53:47 (DM basis). The diets were formulated to supply a similar metabolizable-protein (MP) content, and have a CP concentration of 175 g/kg DM (CON), or 150 g/kg DM (LP = low protein), or LP supplemented with additional barley as a source of starch (+ 64 g/kg DM; LPS) or RPMet (+ 0.3 g/100 g MP; LPM). At the end of the 14-week feeding period, 20 cows (5 per treatment) continued to be fed the same diets for a further 6 d, and total urine output and fecal samples collected. We observed that dietary treatment did not affect DM intake, with a mean of 21.5 kg/d, however, there was an interaction between diet and week with intake being highest in cows fed LPS in wk 4 and CON in wk 9 and 14. Mean milk yield, 4% fat corrected milk and energy corrected milk were not altered by treatment. Similarly, we found no effect of dietary treatment on milk fat, protein or lactose content. In contrast, milk and plasma urea concentrations were highest in cows fed CON. The concentration of blood plasma β-hydroxybutyrate was highest in cows receiving LPM and lowest in LPS. Apparent NUE was 28.6% in cows fed CON, and was higher in cows fed any of the low protein diets (LP, LPS or LPM) with a mean value of 34.2%. The sum of milk fatty acids with a chain length below C16:0 was also highest in cows fed CON. We observed that dietary treatment did not affect the apparent whole-tract nutrient digestibility of organic matter, N, neutral detergent fiber and acid detergent fiber, with mean values of 0.785, 0.659, 0.660 and 0.651 kg/kg respectively, but urinary N excretion was approximately 60 g/d lower in cows fed the low CP diets compared with CON. We conclude that reducing the CP content of red clover and grass silage-based diets from 175 to 150 g/kg DM while maintaining MP supply did not affect performance, but reduced the urinary N excretion and improved NUE, and that supplementing additional starch or RPMet had little further effect.

Lactational performance, enteric methane emission, and nutrient utilization of dairy cows supplemented with botanicals

The objective of this study was to evaluate lactational performance, enteric gas emissions, ruminal fermentation, nutrient use efficiency, milk fatty acid profile, and energy and inflammatory markers in blood of peak-lactation dairy cows fed diets supplemented with Capsicum oleoresin or a combination of Capsicum oleoresin and clove oil. A 10-wk randomized complete block design experiment was conducted with 18 primiparous and 30 multiparous Holstein cows. Cows were blocked based on parity, days in milk, and milk yield (MY), and randomly assigned to 1 of 3 treatments (16 cows/treatment): (1) basal diet (CON); (2) basal diet supplemented with 300 mg/cow per day of Capsicum oleoresin (CAP); and (3) basal diet supplemented with 300 mg/cow per day of a combination of Capsicum oleoresin and clove oil (CAPCO). Premixes containing ground corn (CON), CAP, or CAPCO were mixed daily with the basal diet at 0.8% of dry matter intake (DMI). Supplementation of the diet with CAP or CAPCO did not affect DMI, MY, milk components, and feed efficiency of the cows. Body weight (BW) was increased during the last 2 wk of the experiment by CAP and CAPCO, compared with CON. The botanicals improved BW gain (0.85 and 0.66 kg/d for CAP and CAPCO, respectively, compared with -0.01 kg/d for CON) and CAP enhanced the efficiency of energy utilization, compared with CON (94.5% vs. 78.4%, respectively). Daily CH4 emission was not affected by treatments, but CH4 emission yield (per kg of DMI) and intensity (per kg of MY) were decreased by up to 11% by CAPCO supplementation, compared with CON and CAP. A treatment × parity interaction indicated that the CH4 mitigation effect was pronounced in primiparous but not in multiparous cows. Ruminal molar proportion of propionate was decreased by botanicals, compared with CON. Concentrations of trans-10 C18:1 and total trans fatty acids in milk fat were decreased by CAP and tended to be decreased by CAPCO, compared with CON. Total-tract apparent digestibility of nutrients was not affected by treatments, except for a tendency for decreased starch digestibility in cows supplemented with botanicals. Blood concentrations of β-hydroxybutyrate, total fatty acids, and insulin were not affected by botanicals. Blood haptoglobin concentration was increased by CAP in multiparous but not in primiparous cows. Lactational performance of peak-lactation dairy cows was not affected by the botanicals in this study, but they appeared to improve efficiency of energy utilization and partitioned energy toward BW gain. In addition, CH4 yield and intensity were decreased in primiparous cows fed CAPCO, suggesting a potential positive environmental effect of the combination of Capsicum oleoresin and clove oil supplementation.

Rumen-protected lysine supplementation improved amino acid balance, nitrogen utilization and altered hindgut microbiota of dairy cows

This study was conducted to evaluate the effects of dietary crude protein (CP) and rumen-protected lysine (RPL) supplementation on lactation performance, amino acid (AA) balance, nitrogen (N) utilization and hindgut microbiota in dairy cows. Treatments were in a 2 × 2 factorial arrangement, and the main effects were CP concentration (16% vs. 18%) and RPL supplementation (with or without RPL at 40 g/cow per day). Forty cows were randomly allocated to 4 groups: low-CP diet (LP), low-CP diet plus RPL (LPL), high-CP diet (HP), high-CP diet plus RPL (HPL). The experiment was conducted for 8 weeks. Results showed that RPL increased the dry matter intake (P < 0.01), milk protein yield (P = 0.04) and energy corrected milk (P = 0.04), and tended to increase milk fat yield (P = 0.06) and fat corrected milk (P = 0.05). Cows in the HP group tended to have higher milk urea N (P = 0.07). Plasma concentrations of Arg, Ile, Lys, Met, Pro, total essential AA and total nonessential AA were increased by RPL (P < 0.05). The total essential AA, total nonessential AA and most AA (except Ile, Phe, Gly and Pro) were increased in the HP group (P < 0.05). N excretion was increased in the HP group through an increase in urea N excretion (P < 0.01) and an upward trend in plasma urea N (P = 0.07). In addition, RPL tended to increase milk protein N secretion (P = 0.08), milk N (P = 0.07) and microbial protein synthesis (P = 0.06), and decreased plasma urea N (P < 0.001). In the hindgut, the bacterial community were different between the LP and LPL groups (P < 0.01). The probiotic abundances of Christensenellaceae_R-7_group and Acinetobacter were increased by RPL (P = 0.03 and 0.03, respectively). The pathogenic abundances of Clostridium_sensu_stricto_1 (P < 0.001) and Turicibacter (P < 0.01) were decreased by RPL. In conclusion, supplementing RPL with low dietary CP could balance AA supply and increase milk protein yield, resulting in an improvement in N utilization efficiency, and altered the composition of the hindgut microbiota to favor the lactation performance of dairy cows.

Lactational performance, rumen fermentation, nutrient use efficiency, enteric methane emissions, and manure greenhouse gas-emitting potential in dairy cows fed a blend of essential oils

The objective of this experiment was to investigate the effects of an essential oil (EO) blend on lactational performance, rumen fermentation, nutrient utilization, blood variables, enteric methane emissions and manure greenhouse gas-emitting potential in dairy cows. A randomized complete block design experiment was conducted with 26 primiparous and 22 multiparous Holstein cows. A 2-wk covariate and a 2-wk adaptation periods preceded a 10-wk experimental period used for data and sample collection. Treatments were: (1) basal diet supplemented with placebo (CON); and (2) basal diet supplemented with a blend of EO containing eugenol and geranyl acetate as main compounds. Supplementation with EO did not affect dry matter intake, milk and energy-corrected milk yields, and feed efficiency of cows, compared with CON. Milk fat and lactose concentrations were increased, and milk total solids (TS) concentration and milk fat yield tended to be increased by EO. Multiparous cows supplemented with EO tended to have slightly decreased dry matter and crude protein digestibility compared with CON multiparous cows. There was a tendency for increased ruminal pH by EO, whereas other rumen fermentation variables did not differ between treatments. Daily methane emission was not affected by EO supplementation, but methane emission intensity per kg of milk fat was decreased by 8.5% by EO. Methane emission intensity per kg of milk lactose and milk TS were decreased and methane emission intensity per kg of milk yield tended to be decreased by up to 10% in EO multiparous cows, but not in primiparous cows. The greenhouse gas-emitting potential of manure was not affected by EO supplementation. Compared with CON, fecal nitrogen excretion was increased by EO supplementation in multiparous, but not in primiparous cows, and milk nitrogen secretion (as a % of nitrogen intake) tended to be increased in EO supplemented cows. Blood variables were not affected by EO supplementation in the current study. Overall, dietary supplementation of EO did not affect lactational performance of the cows, although milk fat and lactose concentrations were increased. Most enteric methane emission metrics were not affected, but EO decreased methane intensity per kg of milk fat by 8.5%, compared with the control.

Enhancing Metabolism and Milk Production Performance in Periparturient Dairy Cattle through Rumen-Protected Methionine and Choline Supplementation

For dairy cattle to perform well throughout and following lactations, precise dietary control during the periparturient phase is crucial. The primary issues experienced by periparturient dairy cows include issues like decreased dry matter intake (DMI), a negative energy balance, higher levels of non-esterified fatty acids (NEFA), and the ensuing inferior milk output. Dairy cattle have always been fed a diet high in crude protein (CP) to produce the most milk possible. Despite the vital function that dairy cows play in the conversion of dietary CP into milk, a sizeable percentage of nitrogen is inevitably expelled, which raises serious environmental concerns. To reduce nitrogen emissions and their production, lactating dairy cows must receive less CP supplementation. Supplementing dairy cattle with rumen-protected methionine (RPM) and choline (RPC) has proven to be a successful method for improving their ability to use nitrogen, regulate their metabolism, and produce milk. The detrimental effects of low dietary protein consumption on the milk yield, protein yield, and dry matter intake may be mitigated by these nutritional treatments. In metabolic activities like the synthesis of sulfur-containing amino acids and methylation reactions, RPM and RPC are crucial players. Methionine, a limiting amino acid, affects the production of milk protein and the success of lactation in general. According to the existing data in the literature, methionine supplementation has a favorable impact on the pathways that produce milk. Similarly, choline is essential for DNA methylation, cell membrane stability, and lipid metabolism. Furthermore, RPC supplementation during the transition phase improves dry matter intake, postpartum milk yield, and fat-corrected milk (FCM) production. This review provides comprehensive insights into the roles of RPM and RPC in optimizing nitrogen utilization, metabolism, and enhancing milk production performance in periparturient dairy cattle, offering valuable strategies for sustainable dairy farming practices.

Lactational performance effects of supplemental histidine in dairy cows: A meta-analysis

The objective of this meta-analysis was to examine the effects of supplemental His on lactational performance, plasma His concentration and efficiency of utilization of digestible His (EffHis) in dairy cows. The meta-analysis was performed on data from 17 studies published in peer-reviewed journals between 1999 and 2022. Five publications reported data from 2 separate experiments, which were included in the analyses as separate studies, therefore resulting in a total of 22 studies. In 10 studies, His was supplemented as rumen-protected (RP) His; in 1 study, 2 basal diets with different dHis levels were fed; and in the remaining experiments, free His was infused into the abomasum (4 studies), the jugular vein (3 studies) or deleted from a mixture of postruminally infused AA (4 studies). The main forages in the diets were corn silage in 14 and grass silage in 8 studies. If not reported in the publications, the supplies of dietary CP, metabolizable protein (MP), net energy of lactation, and digestible His (dHis) were estimated using NRC (2001). An initial meta-analysis was performed to test the standard mean difference (SMD; raw mean difference of treatment and control means divided by the pooled standard deviation of the means), that is, effect size, and the corresponding 95% confidence interval (CI) in production parameters between His-supplemented groups versus control. Further, regression analyses were also conducted to examine and compare the relationships between several response variables and dHis supply. Across studies, His supplementation increased plasma His concentration (SMD = 1.39; 95% CI: 1.17-1.61), as well as DMI (SMD = 0.240; 95% CI: 0.051-0.429) and milk yield (MY; SMD = 0.667; 95% CI: 0.468-0.866), respectively. Further, milk true protein concentration (MTP; SMD = 0.236; 95% CI: 0.046-0.425) and milk true protein yield (MTPY; SMD = 0.581; 95% CI: 0.387-0.776) were increased by His supplementation. Notably, the increase in MTP concentration and MTPY were 3.9 and 1.3 times greater for studies with MP-deficient (according to NRC 2001) diets compared with studies with MP-adequate diets. The regression analyses revealed that production parameters (DMI, MY, and MTPY) responded in a nonlinear manner to increasing His supply. Further, we detected a difference in the magnitude of change in MTPY and plasma His concentration with the level of His supply and between His supplementation methods, being greater for infused His compared with RPHis. Lastly, a linear and negative relationship between EffHis and the ratio of total digestible His to net energy for lactation supply was observed, indicating an important interaction between dHis and energy supply and EffHis (i.e., utilization of dHis to support protein export). Overall, these analyses confirm His as an important AA in dairy cattle nutrition.

Production effects of extruded soybean meal replacing canola meal in the diet of lactating dairy cows

This study investigated the effects of extruded soybean meal (ESBM) in comparison with canola meal (CM) fed on an equivalent crude protein (CP) basis on lactational performance and ruminal fermentation of dairy cows. Following a 2-wk covariate period, 48 Holstein cows averaging (±SD): 146 ± 46 d in milk (DIM) and 43 ± 7 kg/d milk yield (MY) were assigned 1 of 2 treatment diets in a randomized complete block design experiment, which included a 2-wk period for dietary treatment adaptation before experimental data were collected. Following the adaptation period, samples and experimental data were collected for a total of 7 wk. Cows were blocked based on parity, DIM, and MY. Treatment diets contained 15.8% CM (containing 41.2% CP) or 13.2% ESBM (with 48.7% CP) of total mixed ration dry matter (DM), with similar inclusion of other feed ingredients. The CM diet was supplemented with canola oil, whereas the ESBM diet was supplemented with soybean hulls to achieve similar ether extract and neutral detergent fiber contents between the diets. Urea and rumen-protected Met and Lys were added to both diets to meet or exceed cow recommendations. Whole-ruminal digesta samples were collected from 10 (5 per treatment) ruminally cannulated cows. Eight cannulated cows were removed during the last week of the experiment to participate in another study. Treatment did not affect DM intake and MY or energy-corrected MY of the cows. Energy-corrected MY, apart from experimental wk 5, was similar between treatments. Apart from experimental wk 3 and 7, milk fat concentration and yield were greater for cows fed ESBM compared with CM. In multiparous cows only, milk true protein yield was greater for cows fed CM compared with ESBM. Ruminal concentration of total volatile fatty acids and the molar proportion of acetate were greater for ESBM, and propionate and valerate were greater in cows fed CM. Acetate to propionate ratio was greater for cows fed ESBM versus CM diet. Compared with the CM diet, the ESBM diet increased plasma concentrations of Ile, Leu, and Phe but not the sum of essential AA. Apparent total-tract digestibility of acid detergent fiber was greater in cows fed ESBM relative to CM. In this experiment, CM and ESBM included on an equal CP basis in the diet of dairy cows, resulted in similar DM intake, MY, and feed efficiency.

Microbial composition, rumen fermentation parameters, enteric methane emissions, and lactational performance of phenotypically high and low methane-emitting dairy cows

This experiment was designed to investigate the relation of high and low methane-yield phenotypes with body weight (BW), dry matter intake (DMI), lactation performance, enteric CH4 emissions, and rumen fermentation parameters in lactating dairy cows. A total of 130 multi- and primiparous Holstein cows were screened for enteric CH4 emissions using the GreenFeed system (C-Lock Inc.). Out of these 130 cows, 5 were identified as phenotypically high (HM) and 5 as phenotypically low (LM) CH4 emitters. Cows in the LM group had lower daily enteric CH4 emissions than cows in the HM group (on average 346 vs. 439 g/d, respectively), lower CH4 yield (15.5 vs. 20.4 g of CH4/kg of DMI), and CH4 intensity (13.2 vs. 17.0 g of CH4/ kg of energy-corrected milk yield). Enteric emissions of CO2 and H2 did not differ between HM and LM cows. These 10 cows were blocked by parity, days in milk, and milk production, and were used in a 5-wk randomized complete block design experiment. Milk composition, production, and BW were also not different between LM and HM cows. The concentration of total volatile fatty acids in ruminal contents did not differ between CH4 phenotypes, but LM cows had a lower molar proportion of acetate (57 vs. 62.1%), a higher proportion of propionate (27.5 vs. 21.6%, respectively), and therefore a lower acetate-to-propionate ratio than HM cows. Consistently, the 16S cDNA analysis revealed the abundance of Succinivibrionaceae and unclassified Veillonellaceae to be higher in LM cows compared with HM cows, bacteria that were positively correlated with ruminal propionate concentration. Notably, Succinivibrionaceae trigger the formation of propionate via oxaloacetate pathway from phosphoenolpyruvate via Enzyme Commission: 4.1.1.49, which showed a trend to be higher in LM cows compared with HM cows. Additionally, LM cows possessed fewer transcripts of a gene encoding for methyl-CoM reductase enzyme compared with HM. In this study, low and high CH4-yield cows have similar production performance and milk composition, but total-tract apparent digestibility of organic matter and fiber fractions was lower in the former group of animals.

Effects of Amount and Profile of Amino Acids Supply on Lactation Performance, Mammary Gland Metabolism, and Nitrogen Efficiency in Holstein Dairy Cows

To evaluate the effects of amount and profile of amino acid (AA) on milk protein yield (MPY), mammary metabolism, and efficiency of nitrogen use (ENU), ten cows were used in 5 × 5 replicated Latin squares and fed a positive control (16.1% crude protein-CP) or two lower CP diets (14.6 and 13.2%) with or without essential AA (EAA) infusion. The EAA solutions provided predicted limiting EAA in each treatment and were continuously infused into the abomasum of the cows. Milk production and MPY were not affected by treatment (mean 35.4 kg/d and 1.03 kg/d, respectively). Efficiency of nitrogen utilization was increased as dietary CP decreased but was not affected by EAA infusion (p < 0.01). Energy-corrected milk production was increased by EAA infusion into 13.2% CP, but not into 14.6% CP diet (p = 0.09), reaching the positive control value. Infusions increased mammary affinity for non-infused EAA (Ile, Phe, Thr, and Trp), allowing the same MPY despite lower arterial concentrations of these AA. Higher arterial concentrations of infused EAA did not increase their mammary uptake and MPY (p = 0.40; p = 0.85). Mammary metabolism did not fully explain changes in N efficiency, suggesting that it might be driven by less extramammary catabolism as AA supply was reduced.

Replacing ground corn with soyhulls plus palmitic acid in low metabolizable protein diets with or without rumen-protected amino acids: Effects on production and nutrient utilization in dairy cows

We previously observed that diets with reduced starch concentration decreased yields of milk and milk protein in dairy cows fed low metabolizable protein diets. Supplementation of reduced-starch diets with a lipid source may attenuate or eliminate production losses. Our objective was to investigate the effects of partially replacing ground corn with soyhulls plus a palmitic acid-enriched supplement on dry matter (DM) intake, milk yield and composition, plasma AA concentration, and N and energy utilization in cows fed low metabolizable protein diets (mean = -68 g/d balance) with or without rumen-protected Met, Lys, and His (RP-MLH). Sixteen multiparous Holstein cows averaging (mean ± standard deviation) 112 ± 28 d in milk, 724 ± 44 kg of body weight, and 46 ± 5 kg/d of milk in the beginning of the study were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Each period lasted 21 d, consisting of 14 d for diet adaptation and 7 d for data and sample collection. Diets were fed as follows: (1) high starch (HS), (2) HS plus RP-MLH (HS+AA), (3) reduced starch plus a palmitic acid-enriched supplement (RSPA), and (4) RSPA plus RP-MLH (RSPA+AA). The HS diet contained (DM basis) 26% ground corn and 7% soyhulls, and the RSPA diet had 10% ground corn, 22% soyhulls, and 1.5% palmitic acid. The HS diet averaged (DM basis) 32.6% starch and 4% ether extract, while starch and ether extract concentrations of the RSPA diet were 21.7 and 5.9%, respectively. All 4 diets had (DM basis) 40% corn silage, 5% mixed-mostly grass haylage, 5% grass hay, and 50% concentrate. Diets did not affect DM intake and milk yield. Contrarily, feeding RSPA and RSPA+AA increased yields of energy-corrected milk (47.0 vs. 44.8 kg/d) and milk fat (1.65 vs. 1.50 kg/d) compared with HS and HS+AA. Milk fat concentration tended to decrease when RP-MLH was supplemented to HS, but no change was seen when added to RS (starch level × RP-MLH interaction). Milk and plasma urea N increased, and milk N efficiency decreased in cows fed RSPA and RSPA+AA versus HS and HS+AA. Apparent total-tract digestibilites of crude protein and neutral detergent fiber, as well as urinary urea N and total N excretion, were greater in cows offered RSPA and RSPA+AA than HS and HS+AA. Plasma Met and His concentrations increased with supplemental RP-MLH. Intake of gross energy and digestible energy and the output of urinary and milk energy were all greater with feeding RSPA and RSPA+AA versus HS and HS+AA. In summary, partially replacing ground corn with soyhulls plus palmitic acid in diets supplemented or not with RP-MLH increased milk fat yield and fiber digestibility and maintained DM intake and milk yield, but with decreased milk N efficiency and elevated urinary N excretion.

Processed fava bean as a substitute for rapeseed meal with or without rumen-protected methionine supplement in grass silage-based dairy cow diets

Fava bean offers a sustainable home-grown protein source for dairy cows, but fava bean protein is extensively degraded in the rumen and has low Met concentration. We studied the effects of protein supplementation and source on milk production, rumen fermentation, N use, and mammary AA utilization. The treatments were unsupplemented control diet, and isonitrogenously given rapeseed meal (RSM), processed (dehulled, flaked, and heated) fava bean without (TFB) or with rumen-protected (RP) Met (TFB+). All diets consisted of 50% grass silage and 50% cereal-based concentrate including studied protein supplement. The control diet had 15% of crude protein and protein-supplemented diets 18%. Rumen-protected Met in TFB+ corresponded to 15 g/d of Met absorbed in the small intestine. Experimental design was a replicated 4 × 4 Latin square with 3-wk periods. The experiment was conducted using 12 multiparous mid-lactation Nordic Red cows, of which 4 were rumen cannulated. Protein supplementation increased dry matter intake (DMI), and milk (31.9 vs. 30.7 kg/d) and milk component yields. Substituting RSM with TFB or TFB+ decreased DMI and AA intake but increased starch intake. There were no differences in milk yield or composition between RSM diet and TFB diets. Rumen-protected Met did not affect DMI, or milk or milk component yields but increased milk protein concentration in comparison to TFB. There were no differences in rumen fermentation except for increased ammonium-N concentration with the protein-supplemented diets. Nitrogen-use efficiency for milk production was lower for the supplemented diets versus control diet but tended to be greater for TFB and TFB+ versus RSM. Protein supplementation increased plasma essential AA concentration but there were no differences between TFB diets and RSM. Rumen-protected Met clearly increased plasma Met concentration (30.8 vs. 18.2 µmol/L) but did not affect other AA. Absence of differences between RSM and TFB in milk production together with limited effects of RP Met suggest that TFB is a potential alternative protein source for dairy cattle.

Effects of Sodium Nitrate and Coated Methionine on Lactation Performance, Rumen Fermentation Characteristics, Amino Acid Metabolism, and Microbial Communities in Lactating Buffaloes

Sodium nitrate is used as a non-protein nitrogen supplement while methionine is considered as a common methionine additive for ruminants. This study investigated the effects of sodium nitrate and coated methionine supplementation on milk yield, milk composition, rumen fermentation parameters, amino acid composition, and rumen microbial communities in lactating buffaloes. Forty mid-lactation multiparous Murrah buffaloes within the initial days in milk (DIM) = 180.83 ± 56.78 d, milk yield = 7.63 ± 0.19 kg, body weight = 645 ± 25 kg were selected and randomly allocated into four groups (N = 10). All of animals received the same total mixed ratio (TMR) diet. Furthermore, the groups were divided into the control group (CON), 70 g/d sodium nitrate group (SN), 15 g/d palmitate coated L-methionine group (MET), and 70 g/d sodium nitrate +15 g/d palmitate coated L-methionine group (SN+MET). The experiment lasted for six weeks, including two weeks of adaption. The results showed that most rumen-free amino acids, total essential amino acids, and total amino acids in Group SN increased (p < 0.05), while the dry matter intake (DMI) and rumen acetate, propionate, valerate, and total volatile fatty acids (TVFA) in Group MET decreased (p < 0.05). However, there was no significant difference in milk yield, milk protein, milk fat, lactose, total solid content, and sodium nitrate residue in milk among groups (p > 0.05). Group SN+MET had a decreased rumen propionate and valerate (p < 0.05), while increasing the Ace, Chao, and Simpson indices of alpha diversity of rumen bacteria. Proteobacteria and Actinobacteriota were significantly increased (p < 0.05) in Group SN+MET, but Bacteroidota, and Spirochaetota were decreased (p < 0.05). In addition, Group SN+MET also increased the relative abundance of Acinetobacter, Lactococcus, Microbacterium, Chryseobacterium, and Klebsiella, which were positively correlated with cysteine and negatively correlated with rumen acetate, propionate, valerate, and TVFA. Rikenellaceae_RC9_gut_group was identified as a biomarker in Group SN. Norank_f__UCG-011 was identified as a biomarker in Group MET. Acinetobacter, Kurthia, Bacillus, and Corynebacterium were identified as biomarkers in Group SN+MET. In conclusion, sodium nitrate increased rumen free amino acids, while methionine decreased dry matter intake (DMI) and rumen volatile fatty acids. The combined use of sodium nitrate and methionine enriched the species abundance of microorganisms in the rumen and affected the composition of microorganisms in the rumen. However, sodium nitrate, methionine, and their combination had no significant effect on the milk yield and milk composition. It was suggested that the combined use of sodium nitrate and methionine in buffalo production was more beneficial.

Feeding lower-protein diets based on red clover and grass or alfalfa and corn silage does not affect milk production but improves nitrogen use efficiency in dairy cows

Reducing the dietary crude protein (CP) concentration can decrease the financial cost and lower the environmental impact of milk production. Two studies were conducted to examine the effects of reducing the dietary CP concentration on animal performance, nutrient digestibility, milk fatty acid (FA) profile, and nitrogen use efficiency (NUE; milk N/N intake) in dairy cows fed legume silage-based diets. Thirty-six multiparous Holstein-Friesian dairy cows that were 76 ± 14 (mean ± SD) days in milk and 698 ± 54 kg body weight were used in a 3 × 3 Latin square design in each of 2 studies, with 3 periods of 28 d. In study 1, cows were fed diets based on a 50:50 ratio of red clover to grass silage [dry matter (DM) basis] containing 1 of 3 dietary CP concentrations: high (H) = 175 g of CP/kg of DM; medium (M) = 165 g of CP/kg of DM; or low (L) = 150 g of CP/kg of DM. In study 2, cows were fed 175 g of CP/kg of DM with a 50:50 ratio of alfalfa to corn silage (H50) or 1 of 2 diets containing 150 g of CP/kg of DM with either a 50:50 (L50) or a 60:40 (L60) ratio of alfalfa to corn silage. Cows in both studies were fed a total mixed ration with a forage-to-concentrate ratio of 52:48 (DM basis). All diets were formulated to meet the MP requirements, except L (95% of MP requirements). In study 1, cows fed L ate 1.6 kg of DM/d less than those fed H or M, but milk yield was similar across treatments. Mean milk protein, fat, and lactose concentrations were not affected by diet. However, the apparent total-tract nutrient digestibility was decreased in cows fed L. The NUE was 5.7 percentage units higher in cows fed L than H. Feeding L also decreased milk and plasma urea concentrations by 4.4 mg/dL and 0.78 mmol/L, respectively. We found no effect of dietary treatment on the milk saturated or monounsaturated FA proportion, but the proportion of polyunsaturated FA was increased, and milk odd- and branched-chain FA decreased in cows fed L compared with H. In study 2, DM intake was 2 kg/d lower in cows receiving L50 than H50. Increasing the alfalfa content and feeding a low-CP diet (L60) did not alter DMI but decreased milk yield and milk protein concentration by 2 kg/d and 0.6 g/kg, respectively, compared with H50. Likewise, milk protein and lactose yield were decreased by 0.08 kg/d in cows receiving L60 versus H50. Diet had no effect on apparent nutrient digestibility. Feeding the low-CP diets compared with H50 increased the apparent NUE by approximately 5 percentage units and decreased milk and plasma urea concentrations by 7.2 mg/dL and 1.43 mmol/L, respectively. Dietary treatment did not alter milk FA profile except cis-9,trans-11 conjugated linoleic acid, which was higher in milk from cows receiving L60 compared with H50. We concluded that reducing CP concentration to around 150 g/kg of DM in red clover and grass or alfalfa and corn silage-based diets increases the apparent NUE and has little effect on nutrient digestibility or milk performance in dairy cows.

Effects of phytonutrients and yeast culture supplementation on lactational performance and nutrient use efficiency in dairy cows

Yeast culture and phytonutrients are dietary supplements with distinct modes of action, and they may have additive effects on the performance of dairy cattle. The objective of this study was to investigate the effects of a preparation of phytonutrients and a yeast culture from Saccharomyces cerevisiae on lactational performance, total-tract digestibility of nutrients, urinary nitrogen losses, energy metabolism markers, and blood cells in dairy cows. Thirty-six mid-lactation Holstein cows (10 primiparous and 26 multiparous) were used in an 8-wk randomized complete block design experiment with a 2-wk covariate period, 2 wk for adaptation to the diets, and a 4-wk experimental period for data and samples collection. Following a 2-wk covariate period, cows were blocked by days in milk, parity, and milk yield and randomly assigned to 1 of 3 treatments (12 cows per treatment): basal diet supplemented with 14 g/cow per day yeast culture (YC; S. cerevisiae), basal diet supplemented with 1.0 g/cow per day phytonutrients (PN; 5.5% cinnamaldehyde, 9.5% eugenol, and 3.5% capsicum oleoresin), or basal diet supplemented with a combination of YC and PN (YCPN). Treatments were top-dressed once daily on the total mixed ration at time of feeding. Dry matter intake, milk yield, and feed efficiency were not affected by treatments. Milk composition and energy-corrected milk yield were also not affected by supplementation of YC, PN, and YCPN. There were no differences in intake or total-tract digestibility of dietary nutrients among treatments. Compared with YC, the PN and YCPN treatments tended to decrease the proportion of short-chain fatty acids in milk fat. There was an additive effect of YC and PN supplementation on urinary urea nitrogen (UUN) excretion relative to total nitrogen intake. Cows fed a diet supplemented with YCPN had lower UUN excretion than cows in YC and tended to have lower UUN excretion compared with PN. Blood monocytes count and percentage were decreased in cows fed PN and YCPN diets compared with YC. Treatments did not affect concentrations of blood β-hydroxybutyrate and total fatty acids. Overall, lactational performance, digestibility of nutrients, energy metabolism markers, and blood cells were not affected by YC, PN, or YCPN supplementation. A combination of PN and YC had an additive effect on nitrogen excretion in dairy cows.

Balancing dairy cattle diets for rumen nitrogen and methionine or all essential amino acids relative to metabolizable energy

Improving the ability of diet formulation models to more accurately predict AA supply while appropriately describing requirements for lactating dairy cattle provides an opportunity to improve animal productivity, reduce feed costs, and reduce N intake. The goal of this study was to evaluate the sensitivity of a new version of the Cornell Net Carbohydrate and Protein System (CNCPS) to formulate diets for rumen N, Met, and all essential AA (EAA). Sixty-four high-producing dairy cattle were randomly assigned to 1 of the 4 following diets in a 14-wk longitudinal study: (1) limited metabolizable protein (MP), Met, and rumen N (Base), (2) adequate Met but limited MP and rumen N (Base + M), (3) adequate Met and rumen N, but limited MP (Base + MU), and (4) adequate MP, rumen N, and balanced for all EAA (Positive). All diets were balanced to exceed requirements for ME relative to maintenance and production, assuming a nonpregnant, 650-kg animal producing 40 kg of milk at 3.05% true protein and 4.0% fat. Dietary MP was 97.2, 97.5, 102.3, and 114.1 g/kg of dry matter intake for the Base, Base + M, Base + MU, and Positive diets, respectively. Differences were observed for dry matter intake and milk yield (24.1 to 24.7 and 39.4 to 41.1 kg/d, among treatments). Energy corrected milk, fat, and true protein yield were greater (2.9, 0.13, and 0.08 kg/d, respectively) in cows fed the Positive compared with the Base diet. Using the updated CNCPS, cattle fed the Base, Base + M, and Base + MU diets were predicted to have a negative MP balance (-231, -310, and -142 g/d, respectively), whereas cattle fed the Positive diet consumed 33 g of MP/d excess to ME supply. Bacterial growth was predicted to be depressed by 16 and 17% relative to adequate N supply for the Base and Base + M diets, respectively, which corresponded with the measured lower apparent total-tract NDF degradation. The study demonstrates that improvements in lactation performances can be achieved when rumen N and Met are properly supplied and further improved when EAA supply are balanced relative to requirements. Formulation using the revised CNCPS provided predictions for these diets, which were sensitive to changes in rumen N, Met, all EAA, and by extension MP supply.

Rumen-Protected Lysine and Methionine Supplementation Reduced Protein Requirement of Holstein Bulls by Altering Nitrogen Metabolism in Liver

The aim of this study was to investigate the effect of low-protein diets supplemented with rumen-protected lysine (RPLys) and methionine (RPMet) on growth performance, rumen fermentation, blood biochemical parameters, nitrogen metabolism, and gene expression related to N metabolism in the liver of Holstein bulls. Thirty-six healthy and disease-free Holstein bulls with a similar body weight (BW) (424 ± 15 kg, 13 months old) were selected. According to their BW, they were randomly divided into three groups with 12 bulls in each group in a completely randomized design. The control group (D1) was fed with a high-protein basal diet (CP13%), while bulls in two low-protein groups were supplied a diet with 11% crude protein and RPLys 34 g/d·head + RPMet 2 g/d·head (low protein with low RPAA, T2) or RPLys 55 g/d·head + RPMet 9 g/d·head (low protein with high RPAA, T3). At the end of the experiment, the feces and urine of dairy bulls were collected for three consecutive days. Blood and rumen fluid were collected before morning feeding, and liver samples were collected after slaughtering. The results showed that the average daily gain (ADG) of bulls in the T3 group was higher than those in D1 (p < 0.05). Compared with D1, a significantly higher nitrogen utilization rate (p < 0.05) and serum IGF-1 content (p < 0.05) were observed in both T2 and T3 groups; however, blood urea nitrogen (BUN) content was significantly lower in the T2 and T3 groups (p < 0.05). The content of acetic acid in the rumen of the T3 group was significantly higher than that of the D1 group. No significant differences were observed among the different groups (p > 0.05) in relation to the alpha diversity. Compared with D1, the relative abundance of Christensenellaceae_R-7_group in T3 was higher (p < 0.05), while that of Prevotellaceae _YAB2003_group and Succinivibrio were lower (p < 0.05). Compared with D1 and T2 group, the T3 group showed an expression of messenger ribonucleic acid (mRNA) that is associated with (CPS-1, ASS1, OTC, ARG) and (N-AGS, S6K1, eIF4B, mTORC1) in liver; moreover, the T3 group was significantly enhanced (p < 0.05). Overall, our results indicated that low dietary protein (11%) levels added with RPAA (RPLys 55 g/d +RPMet 9 g/d) can benefit the growth performance of Holstein bulls by reducing nitrogen excretion and enhancing nitrogen efficiency in the liver.

Implications of supplementing mid-lactation multiparous Holstein cows fed high by-product low-forage diets with rumen-protected methionine and lysine in a commercial dairy

Supplementation of rumen-protected amino acids may improve dairy cow performance but few studies have evaluated the implications of supplementing low-forage diets. Our objective was to evaluate the effects of supplementing rumen-protected methionine (Met) and lysine (Lys) on milk production and composition as well as on mammary gland health of mid-lactating Holstein cows from a commercial dairy farm feeding a high by-product low-forage diet. A total of 314 multiparous cows were randomly assigned to control (CON; 107 g of dry distillers' grains) or rumen-protected Met and Lys (RPML; 107 g dry distillers' grains + 107 g of RPML). All study cows were grouped in a single dry-lot pen and fed the same total mixed ration diet twice a day for a total of 7 weeks. Treatments were top-dressed on the total mix ration immediately after morning delivery with 107 g of dry distillers' grains for 1 week (adaptation period) and then with CON and RPML treatments for 6 weeks. Blood samples were taken from a subset of 22 cows per treatment to determine plasma AA (d 0 and 14) and plasma urea nitrogen and minerals (d 0, 14, and 42). Milk yield and clinical mastitis cases were recorded daily, and milk components were determined bi-weekly. Body condition score change was evaluated from d 0 to 42 of the study. Milk yield and components were analyzed by multiple linear regression. Treatment effects were evaluated at the cow level considering parity and milk yield and composition taken at baseline as a covariate in the models. Clinical mastitis risk was assessed by Poisson regression. Plasma Met increased (26.9 vs 36.0 µmol/L), Lys tended to increase (102.5 vs 121.1 µmol/L), and Ca increased (2.39 vs 2.46 mmol/L) with RPML supplementation. Cows supplemented with RPML had higher milk yield (45.4 vs 46.0 kg/d) and a lower risk of clinical mastitis (risk ratio = 0.39; 95% CI = 0.17-0.90) compared to CON cows. Milk components yield and concentrations, somatic cell count, body condition score change, plasma urea nitrogen, and plasma minerals other than Ca were not affected by RPML supplementation. Results suggest that RPML supplementation increases milk yield and decreases the risk of clinical mastitis in mid-lactation cows fed a high by-product low-forage diet. Further studies are needed to clarify the biological mechanisms for mammary gland responses to RPML supplementation.

Effects of the SLC38A2-mTOR Pathway Involved in Regulating the Different Compositions of Dietary Essential Amino Acids-Lysine and Methionine on Growth and Muscle Quality in Rabbits

In recent years, ensuring food security has been an important challenge for the world. It is important to make good use of China’s domestic local feed resources to provide safe, stable, efficient, and high-quality rabbit meat products for China and the world. Lysine and methionine are the two most limiting essential amino acids in the rabbit diet. However, little is known about the rational composition of lysine and methionine in rabbit diets and the mechanisms that affect growth and development. Accordingly, in this study, we sought to address this knowledge gap by examining the effects of different compositions of lysine and methionine in rabbit diets. Subsequently, the growth status, nitrogen metabolism, blood biochemical indexes, muscle development, muscle quality, and the growth of satellite cells were evaluated in the animals. The results showed that diets containing 0.80% Lys and 0.40% Met improved average daily weight gain, feed conversion, nitrogen use efficiency, and muscle quality in the rabbits (p < 0.05). Additionally, it altered the amino acid transport potential in muscle by upregulating the expression of the SLC7A10 gene (p < 0.05). Meanwhile, the cell viability and the rate of division and migration of SCs in the 0.80% Lys/0.40 % Met composition group were increased (p < 0.05). SLC38A2 and P−mTOR protein expression was upregulated in the 0.80% lysine/0.40% methionine composition group (p < 0.05). In conclusion, 0.80% Lys/0.40% Met was the most suitable lysine and methionine composition in all tested diets. SLC38A2 acted as an amino acid sensor upstream of mTOR and was involved in the 0.80% Lys/0.40% Met regulation of muscle growth and development, thus implicating the mTOR signaling pathway in these processes.

Effects of methionine, leucine, and insulin on circulating concentrations and mammary extraction of energy substrates and amino acids in lactating dairy cows

The aim of this experiment was to test whether insulin potentiates the effects of two abomasally infused amino acids (AA), leucine and methionine (LM), on mammary extraction efficiency of energetic and nitrogenous nutrients. Six lactating Holstein cows (155 ± 9 DIM) were ruminally-cannulated and had the right carotid artery subcutaneously transposed. Cows were fed a 20% metabolizable protein-restricted diet and abomasally infused with water (8 L/d) or AA (Met 26 g/d, Leu 70 g/d) for 8 h/d, for 7 days. On the last day of each period, cows were intravenously infused with saline (0.9% NaCl, 110 mL/h) or subjected to 8 h hyperinsulinemic clamp (IC) alongside abomasal infusions. For IC, insulin was infused at 1 µg/kg/h. Normoglycemia was maintained by varying glucose (50% w/v in water) infusion rate based on coccygeal vein glucose concentration. Carotid arterial and subcutaneous abdominal (mammary) vein blood samples were collected at 0, 1, 2, 4, and 6 h from the start of infusions. Milk weights and samples for baseline measurements of production were taken on day 5 PM, day 6 AM and PM, and day 7 AM of the experimental period. A final milk weight and sample was taken immediately after abomasal and intravenous infusions on day 7 PM for assessing the interaction between insulin and the infused AA. The experiment had an incompletely replicated Latin square design with a 2 × 2 factorial arrangement of treatments (abomasal and intravenous infusion). Baseline milk production when cows were only receiving abomasal infusions was largely unaffected by LM, but milk protein yield tended to be decreased. On day 7, LM tended to positively increase milk fat and de novo fatty acid content, and IC tended to decrease milk protein content. Both milk urea nitrogen and plasma urea nitrogen were decreased by IC. Circulating AA concentrations in plasma were decreased by both LM and IC, but mammary extraction efficiency was affected by neither. Infusion of LM had no effect on any energy metabolite analyzed. Circulating non-esterified fatty acid concentration was decreased by IC, with no effect on mammary extraction efficiency. Mammary extraction efficiency of both acetate and β-hydroxybutyrate were decreased by IC. Overall, while both circulating concentrations of energy metabolites and amino acids were decreased in response to treatments, this was not due to improved mammary extraction efficiency.

Potential benefits of amino acid supplementation for cervid performance and nutritional ecology, with special focus on lysine and methionine: A review

Deer farming is a thriving industry for venison, velvet antlers, trophy hunting, and other by-products. Feeding and nutrition are important factors for improving production performance, especially dietary protein and amino acids (AAs), as they are the main components of all tissues. Only a few studies on AA supplementation (Lys, Met, Arg) have been performed on cervids, which show positive effects on weight gain, ADG, feed-:gain ratio, plasma AAs, carcass weight, dressing percentage, yield of high-quality muscles, storage of internal fat during winter, DM and CP digestibility, plasma protein- and fat-related metabolite concentrations, antler burr perimeter, weight, length and mineralisation, velvet antler yield, rumen volatile fatty acids, and microbiome composition. All these effects are relevant for supporting the production of cervids products, from venison to velvet or trophy antlers, as well as their general performance and well-being of captive-bred cervids. The current available information suggests that AA supplementation can be especially interesting for animals fed low protein rations, and growing animals, but should be avoided in high rations and during winter, since it may promote the accumulation of internal fat. Potential effects on milk production and the concentrations of different hormones involved in the regulation of the antler cycle should be further explored.

In situ and in vitro evaluation of the bioavailability of rumen-protected methionine with coating prototypes

Rumen protected amino acids are supplements that can enhance ruminal performance, yet the coating designed to protect the amino acids might also lead to different effects. Methionine is an essential methyl donor to synthesize protein, and little data exists on the effects of coating materials on its bioavailability. The purpose of this study was to estimate the effect of rumen-protected methionine (RPM) coatings with different ratios of acrylic resin IV (AR), ethyl cellulose (EC), and a mixture of AR and EC (AREC). Fifteen RPMs were prepared according to a single factor design, with 5 proportions each of AR, EC, and AREC to DL-methionine (DL-Met). Twelve hybrid small-tailed Han sheep with rumen fistula were utilized to evaluate in situ escape of RPMs, followed by in vitro abomasum-intestinal release of the RPMs. The results showed a regular variation in both ruminal disappearance and gastrointestinal release of RPMs with different coating prototypes and retention time. The RPMs that were EC and AREC coated presented high bioavailability compared to those with AR. Bioavailability of RPMs was optimal with the 2:20 AREC: DL-Met ratio, when the proportion of AR:EC is 1:1. Additionally, RPMs with a 1:3 ratio of AR:EC confirmed the optimum effect for the RPM of 2:20 AREC: DL-Met. In conclusion, an RPM with a lower AREC ratio coating can achieve better bioavailability and is synergistic to those with EC and AR.

Effects of an exogenous enzyme preparation extracted from a mixed culture of Aspergillus spp. on lactational performance, metabolism, and digestibility in primiparous and multiparous cows

The objective of this study was to investigate the effects of an exogenous enzyme preparation from Aspergillus oryzae and Aspergillus niger on lactational performance of dairy cows. Forty-eight Holstein cows (32 primiparous and 16 multiparous) averaging (± SD) 36.3 ± 8.7 kg/d milk yield and 141 ± 52 d in milk were enrolled in a 10-wk randomized complete block design experiment (total of 24 blocks) and assigned to 1 of 2 treatments: basal diet, no enzyme supplementation (CON) or the basal diet supplemented with 4.2 g/kg dry matter intake (DMI) of an exogenous enzyme preparation containing amylolytic and fibrolytic activities (ENZ). After a 2-wk covariate period, premixes with the enzyme preparation or control were top-dressed daily by mixing with approximately 500 g of total mixed ration. Production data were collected daily and averaged by week. Milk samples were collected every other week, and milk composition was averaged by week. Blood, fecal, and urine samples were collected over 2 consecutive days at 0, 4, 8, 12, and 36 h after feeding during the last week of the experiment. Compared with CON, cows fed ENZ tended to increase DMI and had increased milk concentrations of true protein, lactose, and other solids. Milk fat content tended to be higher in CON cows. A treatment × parity interaction was found for some of the production variables. Primiparous cows receiving ENZ had greater yields of milk, energy-corrected milk, milk true protein, and lactose compared with CON primiparous cows; these production variables did not differ between treatments for multiparous cows. Intake and total-tract digestibility of nutrients did not differ between treatments. Concentrations of blood glucose and total fatty acids were not affected by ENZ supplementation, but β-hydroxybutyrate concentration tended to be greater in ENZ cows. Overall, the exogenous enzyme preparation used in this study increased milk protein and lactose concentrations in all cows, and milk production in primiparous but not multiparous cows. The differential production response between primiparous and multiparous cows was likely a result of a greater increase in DMI with ENZ supplementation in the younger animals.

Assessing Amino Acid Metabolism in Splanchnic Tissues and Mammary Glands to Short-Term Graded Removal of Lys From an Abomasal-Infused Amino Acid Mixture in Lactating Goats

To investigate the responses of amino acid metabolism in portal-drained viscera (PDV), liver, and mammary glands (MGs) to a graded gradual decrease of post-ruminal Lys supply, four multi-catheterized lactating goats were used in a 4 × 4 Latin square experiment. Goats were fasted for 12 h and then received a 33-h abomasal infusion of an amino acid mixture and glucose. Treatments consisted of a graded decrease of Lys content in the infusate to 100 (complete), 60, 30, or 0% as in casein. Lys-removed infusions decreased the production of milk, milk protein, fat, and lactose linearly and also decreased arterial Lys concentrations linearly (p &lt; 0.05). Net PDV uptake decreased linearly (p &lt; 0.05) with decreasing PDV loss ratio (p &lt; 0.05). Although liver removal of Lys decreased linearly (p &lt; 0.05), the removal ratio relative to portal absorption changed small, which was about 10% in all four treatments. Reduced Lys supply resulted in a linear decrease in the utilization of Lys in the peripheral tissues (except mammary, p &lt; 0.05) and the release of more Lys in MGs. Although net mammary uptake of Lys declined linearly (p &lt; 0.05), lactating goats can partially offset the negative effect of decreased circulating Lys concentrations by increasing mammary affinity (p &lt; 0.05) and increasing mammary blood flow (p &lt; 0.05). Graded removal of Lys from the infusate linearly decreased mammary uptake-to-output ratios of Lys (p &lt; 0.05) suggesting that mammary catabolism of Lys decreased. Meanwhile, the treatments linearly increased circulating concentrations of glucagon and linearly decreased prolactin (p &lt; 0.05). In conclusion, the results of the present study indicated that there were several mechanisms used to mitigate a Lys deficiency, including reduced catabolism of Lys in PDV and peripheral tissues (including MGs) and linearly increased mammary blood flow and mammary affinity together with increased mammary uptake and U:O of branched-chain amino acids (BCAA). Given these changes, the decline in milk protein production could be attributed to the combined effect of mass action with Lys and hormonal status.

Feasibility of Supplying Ruminally Protected Lysine and Methionine to Periparturient Dairy Cows on the Efficiency of Subsequent Lactation

The objective of this study was to evaluate the effects of supplying ruminally protected Lys (RPL) and ruminally protected Met (RPM) to transition cows' diets on the efficiency of subsequent lactation. A total of 120 prepartum Holstein cows were assigned into four treatments blocked by the anticipated calving date, previous lactation milk yield, number of lactations, and body condition score and fed either RPL, RPM, or the combination (RPML) or control diet (CON) throughout the transition period (3 weeks before till 3 weeks after calving). From 22 to 150 days in milk (DIM), all animals (100 cows) were fed a combination of RPM and RPL (0.17% RPM and 0.41% RPL of DM; n = 25 cows/treatment) as follows; CON–RPML, RPM–RPML, RPL–RPML, and RPML–RPML. Milk production and dry matter intake (DMI) were measured daily; milk and blood samples were taken at 21, 30, 60, 90, 120, and 150 DIM. Supplemented amino acids (AA) were mixed with the premix and added to the total mixed ration during the experiment. DMI (p &lt; 0.001) and energy-corrected milk (ECM, p = 0.04) were higher for cows that were fed RPML–RPML than other cows. Compared with CON–RPML, yields of milk total protein, lactose, and nitrogen efficiency were increased (p &lt; 0.01), whereas milk urea nitrogen (MUN; p = 0.002) was decreased for other treatments. However, supplemental AA did not affect milk lactose percentage, fat yield, feed efficiency, or serum total protein concentration (p &gt; 0.10). Transition cows that consumed AA had a greater peak of milk yield (p &lt; 0.01), as well as quickly reached the peak of milk (p &lt; 0.004). There were differences in β-hydroxybutyrate concentration during the early lactation, with a lower level for AA groups (p &lt; 0.05), and the difference faded with the progression of lactation (p &gt; 0.10). Fertility efficiency as measured by pregnancy rate was improved by supplemental AA during the perinatal period (p &lt; 0.05). In conclusion, transition cows consumed RPM and RPL, increased post-calving DMI, milk production, milk protein yield, nitrogen efficiency, and improved fertility performance.

Supplementing Ruminally Protected Lysine, Methionine, or Combination Improved Milk Production in Transition Dairy Cows

The objectives of this study were to evaluate the effects of dietary supplementation of ruminally protected lysine (RPL), or methionine (RPM), and their combination (RPML) on the production efficiency of transition cows. A total of 120 pre-partum multiparous Holstein cows were assigned to four treatments based on previous lactation milk production, days (d) of pregnancy, lactation, and body condition score (BCS). Cows were fed a basal diet [pre-calving: 1.53 Mcal/kg dry matter (DM) and post-calving: 1.70 Mcal/kg DM] with or without supplemental ruminally protected amino acids (RPAA). Treatments were the basal diets without supplemental amino acids (CONTROL, n = 30), with supplemental methionine (RPM, pre-calving at 0.16% of DM and post-calving at 0.12% of DM, n = 30), with supplemental lysine (RPL, pre-calving at 0.33% of DM and post-calving at 0.24% DM, n = 30), and the combination (RPML, pre-calving at 0.16% RPM + 0.33% RPL of DM and post-calving at 0.12% RPM + 0.24 % RPL DM, n = 30). The dietary content of lysine was balanced to be within 6.157.2% metabolizable protein (MP)-lysine and that of methionine was balanced within 2.1-2.35% MP-methionine. Dry matter intake (DMI) was measured daily. Milk samples were taken on d 7, 14, and 21 days relative to calving (DRC), and milk yields were measured daily. Blood samples were taken on d -21, -14, -7 before expected calving and d 0, 7, 14, and 21 DRC. Data were analyzed using SAS software. There were significant Trt × time interactions (P < 0.01) for DMI pre- and post-calving period. The CON cows had lower DMI than RPM, RPL, and RPML, both pre-calving (P < 0.01) and post-calving periods (P < 0.01). Energy-corrected milk (P < 0.01), milk fat (P < 0.01), protein (P = 0.02), and lactose (P < 0.01) percentage levels were greater for RPM, RPL, and RPML cows compared to CON. Supplementing RPAA assisted in maintaining BCS post-calving than CON (P < 0.01). Blood concentrations of β-hydroxybutyrate decreased with RPM or RPL or the combination pre-calving (P < 0.01) and tended to decrease post-calving (P = 0.10). These results demonstrated that feeding RPL and RPM improved DMI and milk production efficiency, maintained BCS, and reduced β-hydroxybutyrate concentrations of transition cows.

Harnessing the Value of Rumen Protected Amino Acids to Enhance Animal Performance – A Review

In general, higher mammals need nine amino acids (AA) in their diets as building blocks to synthesize proteins while ruminants can produce some of them through the synthesis of microbial proteins. Diet is utilized by ruminal microorganisms to synthesize microbial protein (MCP) which is digested in the small intestine (SI). Although protein and amino acid requirements in ruminants are subject to microbial protein synthesis, it is not enough for optimal daily production. Therefore, there is a current trend towards supplementing amino acids in ruminant diets. In the rumen, free amino acids can be degraded by rumen bacteria, therefore, the AAs need to be supplemented in a protected form to be stable in the rumen and absorbable post-ruminal for metabolic purposes. The main site of amino acid absorption is the small intestine (SI), and there is a need to keep AA from ruminal degradation and direct them to absorption sites. Several approaches have been suggested by feed scientists to decrease this problem such as defaunation and debacterization of the rumen against amino acid-fermenting fungi and bacteria, inhibitors or antagonists of vitamin B6 enzymes, diet composition and also protecting AA from rumen degradation. A number of studies have evaluated the roles of amino acids concerning their effects on milk yield, growth, digestibility, feed intake and efficiency of nitrogen utilization of ruminants. The focus of this review was on experimental and research studies about AAs in feedstuff, metabolism, supplementing amino acids for ruminants and the current trends of using rumen protected amino acids.

Effects of rumen-protected glutamate supplementation during the periparturient period on digestibility, inflammation, metabolic responses, and performance in dairy cows

The objective of this study was to evaluate the effects of feeding rumen-protected glutamate during the periparturient period (d -21 ± 3 to d 21 ± 3 relative to calving) on apparent total-tract digestibility (ATTD), inflammation, metabolic responses, and production performance of dairy cows. Fifty-two multiparous Holstein cows were blocked by parity, body condition score, and expected calving date, and randomly assigned to one of the experimental diets with rumen-protected monosodium glutamate (RP-Glu; intestinally available Glu = 8.8%) or without RP-Glu (control) at d -21 ± 3 relative to expected calving date. The RP-Glu was fed at 4% and 3% of dietary dry matter, before and after calving, respectively. Prepartum diets contained 17.1% and 16.5% crude protein, and 13.1% and 13.3% starch, and postpartum diets contained 18.8% and 18.3% crude protein, and 22.5% and 22.7% starch on a dry matter basis, respectively for RP-Glu and control treatments. A subset of 19 cows was used to measure ATTD. Cows fed the RP-Glu had greater ATTD of dry matter (70.6 vs. 69.1%), crude protein (75.1 vs. 72.6%), and ether extract (66.0 vs 61.2%) on d 5 ± 1 after calving. Cows fed the RP-Glu also had greater dry matter intake (15.7 vs. 13.7 kg/d) on d 1 after calving. Cows fed the RP-Glu had greater plasma concentrations of Glu (4.60 vs. 3.89 µmol/dL) and insulin-like growth factor-1 (44.2 vs. 30.1 mg/mL), lower serum concentrations of free fatty acids (670 vs. 981 μEq/L) and total bilirubin (0.22 vs. 0.34 mg/dL), and lower plasma 3-methylhistidine concentration (1.28 vs. 1.50 μmol/dL) on d 4 after calving. However, these treatment effects observed between d 1 and d 5 ± 1 immediately after calving did not continue until d 21 after calving. Concentrations of serum amyloid A, serum haptoglobin, and plasma lipopolysaccharide binding protein were not affected by the treatment. In addition, no differences were observed for serum β-hydroxybutyrate concentration and milk yield during the postpartum period between the 2 groups, and cows fed the RP-Glu had a decreased lactose yield. These findings suggest that feeding RP-Glu during the periparturient period can increase digestive capacity and feed intake, and decrease mobilization of body fat and protein immediately after calving without increasing milk production.

Performance of dairy cows fed normal- or reduced-starch diets supplemented with an exogenous enzyme preparation

The objective of this study was to investigate the effects of supplementation of an exogenous enzyme preparation (EEP) on performance, total-tract digestibility of nutrients, plasma AA profile, and milk fatty acids composition in lactating dairy cows fed a reduced-starch diet compared with a normal-starch diet (i.e., positive control). Forty-eight Holstein cows (28 primiparous and 20 multiparous) were enrolled in a 10-wk randomized complete block design experiment with 16 cows per treatment. Treatments were as follows: (1) normal-starch diet (control) containing (% dry matter basis) 24.8% starch and 33.0% neutral detergent fiber (NDF), (2) reduced-starch diet (RSD) containing 18.4% starch and 39.1% NDF, or (3) RSD supplemented with 10 g/cow per day of an EEP (ENZ). The EEP contained amylolytic and fibrolytic activities and was top-dressed on the total mixed ration at the time of feeding. Compared with normal-starch diet, dry matter intake and milk and energy-corrected milk (ECM) yields were lower (on average by 7.1, 9.5, and 7.2%, respectively) for cows on the RSD treatments. Concentrations, but not yields, of milk fat and total solids were increased by RSD. Energy-corrected milk feed efficiency did not differ among treatments. Total-tract digestibility of NDF tended to increase by RSD treatments. Plasma AA concentrations were not affected by treatment, except that of 3-methylhistidine was increased by ENZ, compared with RSD. Blood glucose concentration tended to be lower in cows on the RSD treatments, but ENZ increased glucose and tended to increase insulin concentrations at 4 h after feeding when compared with RSD. Cows on the RSD treatments had decreased concentrations of de novo fatty acids and tended to have increased concentrations of preformed fatty acids in milk. Overall, decreasing dietary starch concentration by 26% decreased dry matter intake, milk, and ECM yields, but ECM feed efficiency was not different among treatments. The negative effects of reducing dietary starch on production were not attenuated by the EEP.

Ruminal protein degradability of sunflower cake, and effects of feeding sunflower cake on nutrient digestion, nitrogen balance, rumen fermentation, and blood metabolites compared with soybean meal

The ruminal degradation parameters of sunflower cake (SFC), a by-product left after the mechanical extraction of oil from sunflower seeds, were estimated in an in situ experiment using a cow. And also the effect of feeding SFC on nutrient digestibilities, digestible energy, nitrogen balance, and ruminal and blood properties were investigated in a feeding trial using four Shiba goats compared isonitrogenously with soybean meal (SBM). The in situ results demonstrated that the SFC had high soluble protein (>70%) with 97% total degradable protein. The feeding trial revealed that the SFC had 85% crude protein digestibility and 65% total digestible nutrients on a dry matter basis in which the low carbohydrate digestibilities offset the advantage of high digestible fat (9.9%). The nitrogen efficiency (retained N/intake N) was lower for SFC than SBM, probably because of an inferior biological value of amino acids in SFC. Among the ruminal and blood properties, only the total ruminal acid concentration and blood urea nitrogen (BUN) differed significantly between the diets: The SFC diet showed lower values than the SBM diet. These findings indicate that SFC can safely replace SBM.

Lactational performance of dairy cows in response to supplementing N-acetyl-l-methionine as source of rumen-protected methionine

The objective of this experiment was to evaluate the effects of supplementing a rumen-protected source of Met, N-acetyl-l-methionine (NALM), on lactational performance and nitrogen metabolism in early- to mid-lactation dairy cows. Sixty multiparous Holstein dairy cows in early lactation (27 ± 4.3 d in milk, SD) were assigned to 4 treatments in a randomized complete block design. Cows were blocked by actual milk yield. Treatments were as follows: (1) no NALM (control); (2) 15 g/d of NALM (NALM15); (3) 30 g/d of NALM (NALM30); and (4) 45 g/d of NALM (NALM45). Diets were formulated using a Cornell Net Carbohydrate and Protein System (CNCPS) v.6.5 model software to meet or exceed nutritional requirements of lactating dairy cows producing 42 kg/d of milk and to undersupply metabolizable Met (control) or supply incremental amounts of NALM. The digestible Met (dMet) supply for control, NALM15, NALM30, and NALM45 were 54.7, 59.8, 64.7, and 72.2 g/d, respectively. The supply of dMet was 88, 94, 104, and 115% of dMet requirement for control, NALM15, NALM30, and NALM45, respectively. Milk yield data were collected, dry matter intake (DMI) was measured daily, and milk samples were collected twice per week for 22 wk. Blood, ruminal fluid, urine, and fecal samples were collected during the covariate period and during wk 4, 8, and 16. Data were analyzed using the GLIMMIX procedure of SAS (SAS Institute) using covariates in the model for all variables except body weight. Linear, quadratic, and cubic contrasts were also tested. Treatments did not affect DMI, milk yield, and milk component concentration and yield; however, feed efficiency expressed as milk yield per DMI and 3.5% fat-corrected milk per DMI were quadratically affected, with greater response observed for NALM15 and NALM30 compared with control. Acetate proportion linearly increased, whereas propionate proportion linearly decreased with NALM supplementation. Blood urea nitrogen linearly decreased with NALM supplementation. Total plasma essential AA concentrations were quadratically affected, as greater values were observed for control and NALM45 than other treatments. Plasma Met concentration was quadratically affected as lower levels were observed with NALM15, whereas Met concentrations increased with NALM45 compared with control. Nitrogen utilization efficiency and apparent total-tract nutrient digestibility were not affected by treatment. Supplementation of NALM at 15 or 30 g/head per day resulted in the greatest improvements in feed efficiency without affecting N metabolism of early- to mid-lactation dairy cows.

Effects of Microencapsulated Methionine on Milk Production and Manure Nitrogen Excretions of Lactating Dairy Cows

Simple Summary

Methionine (Met) deficiency in the diet can limit milk protein production and lead to excessive nitrogen (N) excretions to the environment by dairy cows. We demonstrated that the supplementation of a new rumen-protected Met product to a Met deficient diet increased milk protein yield and decreased manure N excretions of high producing dairy cows. Increased blood flow to the mammary glands and increased apparent total tract digestibility of dietary crude protein seem to be the underlying mechanisms for those improvements in production and the environmental sustainability.

Abstract

The study objective was to determine the effects of rumen-protected methionine (Met) by microencapsulation (RPM) on amino acid (AA) supply to the udder, milk production, and manure nitrogen (N) losses of dairy cows. A corn and soybean-based diet deficient in metabolizable Met (~10 g/d) was supplemented with RPM providing 0, 11.0, 19.3, and 27.5 g/d of Met. Dry matter intake (DMI), milk production, plasma essential AA (EAA), mammary plasma flow (MPF), and fecal (FN) and urinary N (UN) outputs (g/d) were determined. The RPM increased linearly milk yield, milk protein yield, and energy corrected milk yield (p < 0.040) without affecting DMI. Milk protein yield increased by 50 g/d for the 19.3 vs. 0 g/d dose (p = 0.006) but the rate of increment decreased for 27.5 g/d dose. Plasma Met, and MPF increased linearly with RPM dose (p < 0.050). Apparent total tract digestibility of crude protein (p = 0.020) and FN (p = 0.081) decreased linearly with RPM. The UN did not change but total manure N decreased linearly with RPM (p = 0.054). The RPM (19.3 g/d) seemed to help cows overcome the metabolizable Met deficiency while mitigating manure N excretions to the environment.

Enhanced supply of methionine regulates protein synthesis in bovine mammary epithelial cells under hyperthermia condition

Recent evidence has shown that methionine (Met) supplementation can improve milk protein synthesis under hyperthermia (which reduces milk production). To explore the mechanism by which milk protein synthesis is affected by Met supplementation under hyperthermia, mammary alveolar (MAC-T) cells were incubated at a hyperthermic temperature of 42°C for 6 h in media with different concentrations of Met. While the control group (CON) contained a normal amino acid concentration profile (60 μg/mL of Met), the three treatment groups were supplemented with Met at concentrations of 10 μg/mL (MET70, 70 μg/mL of Met), 20 μg/mL (MET80, 80 μg/mL of Met), and 30 μg/mL (MET90,90 μg/mL of Met). Our results show that additional Met supplementation increases the mRNA and protein levels of BCL2 (B-cell lymphoma-2, an anti-apoptosis agent), and decreases the mRNA and protein levels of BAX (Bcl-2-associated X protein, a pro-apoptosis agent), especially at an additional supplementary concentration of 20 μg/mL (group Met80). Supplementation with higher concentrations of Met decreased the mRNA levels of Caspase-3 and Caspase-9, and increased protein levels of heat shock protein (HSP70). The total protein levels of the mechanistic target of rapamycin (mTOR) and the mTOR signalling pathway-related proteins, AKT, ribosomal protein S6 kinase B1 (RPS6KB1), and ribosomal protein S6 (RPS6), increased with increasing Met supplementation, and peaked at 80 μg/mL Met (group Met80). In addition, we also found that additional Met supplementation upregulated the gene expression of αS1-casein (CSN1S1), β-casein (CSN2), and the amino acid transporter genes SLC38A2, SLC38A3 which are known to be mTOR targets. Additional Met supplementation, however, had no effect on the gene expression of κ-casein (CSN3) and solute carrier family 34 member 2 (SLC34A2). Our results suggest that additional Met supplementation with 20 μg/mL may promote the synthesis of milk proteins in bovine mammary epithelial cells under hyperthermia by inhibiting apoptosis, activating the AKT-mTOR-RPS6KB1 signalling pathway, and regulating the entry of amino acids into these cells.

Production effects and bioavailability of N-acetyl-l-methionine in lactating dairy cows

Two experiments were conducted to investigate the production effects of N-acetyl-l-methionine (NALM; experiment 1) and to estimate its bioavailability (BA) and rumen escape (RE; experiment 2), respectively, in lactating dairy cows. In experiment 1, 18 multiparous Holstein cows were used in a replicated, 3 × 3 Latin square design experiment with three 28-d periods. Treatments were (1) basal diet estimated to supply 45 g/d digestible Met (dMet) or 1.47% of metabolizable protein (MP; control), (2) basal diet top-dressed with 32 g/d of NALM to achieve dMet supply of 2.2% of MP, and (3) basal diet top-dressed with 56 g/d of NALM to achieve dMet supply of 2.6% of MP. The NALM treatments supplied estimated 17 and 29 g/d dMet from NALM, respectively, based on manufacturer's specifications. In experiment 2, 4 rumen-cannulated lactating Holstein cows were used in a 4 × 4 Latin square design experiment with four 12-d periods. A 12-d period for baseline data collection and 4 d for determination of RE of NALM preceded the Latin square experiment. For determination of RE, 30 g of NALM were dosed into the rumen simultaneously with Cr-EDTA (used as a rumen fluid kinetics marker) and samples of ruminal contents were collected at 0 (before dosing), 1, 2, 4, 6, 8, 10, 14, 18, and 24 h after dosing. Rumen escape of NALM was calculated using the estimated passage rate based on the measured Cr rate of disappearance. Bioavailability of abomasally dosed NALM was determined using the area under the curve of plasma Met concentration technique. Two doses of l-Met (providing 7.5 and 15 g of dMet) and 2 doses of NALM (11.2 and 14.4 g dMet) were separately pulse-dosed into the abomasum of the cows and blood was collected from the jugular vein for Met concentration analysis at 0 (before dosing), 1, 2, 4, 6, 8, 10, 12, 14, 18, and 24 h after dosing. Supplementation of NALM did not affect DMI, milk yield, feed efficiency, or milk protein and lactose concentrations and yields in experiment 1. Milk fat concentration and energy-corrected milk yield decreased linearly with NALM dose. Plasma Met concentration was not affected by NALM dose. The estimated relative BA of abomasally dosed NALM (experiment 2) was 50% when dosed at 14.4 g/cow (11.2 g/d dMet from NALM) and 24% when dosed at 28.8 g/cow (14.4 g/d dMet from NALM). The estimated RE of NALM was 19% based on the measured k_p of Cr at 11%/h. The total availability of ingested NALM was estimated at 9.5% for the lower NALM dose when taking into account RE (19%) and bioavailability in the small intestine (50%). Overall, NALM supplementation to mid-lactation dairy cows fed a MP-adequate basal diet below NRC (2001) recommendations (45 g/d or 1.47% Met of MP) decreased milk fat and energy-corrected milk yields but did not affect milk or milk true protein yields. Further evaluation of BA of NALM at different doses is warranted. In addition, intestinal conversion of NALM to Met needs additional investigation to establish a possible saturation of the enzyme aminoacylase I at higher NALM doses.

Lactational performance and plasma and muscle amino acid concentrations in dairy cows fed diets supplying 2 levels of digestible histidine and metabolizable protein

The objective of this experiment was to investigate the effect of dietary levels of digestible histidine (dHis) and MP on lactational performance and plasma and muscle concentrations of free AA in dairy cows. A randomized block design experiment was conducted with 48 Holstein cows, including 20 primiparous, averaging (±SD) 103 ± 22 d in milk and 45 ± 9 kg/d milk yield at the beginning of the experiment. A 2-wk covariate period preceded 12 experimental wk, of which 10 wk were for data and sample collection. Experimental treatments were (1) MP-adequate (MPA) diet with 2.1% dHis of MP (MPA2.1), (2) MPA with 3.0% dHis (MPA3.0), (3) MP-deficient (MPD) diet with 2.1% dHis (MPD2.1), and (4) MPD with 3.0% dHis (MPD3.0). Actual dHis supply was estimated at 64, 97, 57, and 88 g/d, respectively. Diets supplied MP at 110% (MPA) and 96% (MPD) of NRC 2001 dairy model requirements calculated based on DMI and production data during the experiment. Dry matter intake and milk yield data were collected daily, milk samples for composition and blood samples for AA analysis were collected every other week, and muscle biopsies at the end of covariate period, and during wk 12 of the experiment. The overall DMI was not affected by dHis or MP level. Milk yield tended to be increased by 3.0% dHis compared with 2.1% dHis. Milk true protein concentration and yield were not affected by treatments, whereas milk urea nitrogen concentration was lower for MPD versus the MPA diet. Milk fat concentration was lower for MPD versus MPA. There was a MP × dHis interaction for milk fat yield and energy-corrected milk; milk fat was lower for MPD3.0 versus MPD2.1, but similar for cows fed the MPA diet regardless of dHis level whereas energy-corrected milk was greater for MPA3.0 versus MPA2.1 but tended to be lower for MPD3.0 versus MPD2.1. Plasma His concentration was greater for cows fed dHis3.0, and concentration of sum of essential AA was greater, whereas carnosine, 1-Methyl-His and 3-Methyl-His concentrations were lower for cows fed MPA versus MPD diet. Muscle concentration of His was greater for cows fed dHis3.0 treatment. The apparent efficiency of His utilization was increased at lower MP and His levels. Overall, cows fed a corn silage-based diet supplying MP at 110% of NRC (2001) requirements tended to have increased ECM yield and similar milk protein yield to cows fed a diet supplying MP at 96% of requirements. Supplying dHis at 3.0% of MP (or 86 and 96 g/d, for MPD3.0 and MPA3.0, respectively) tended to increase milk yield and increased plasma and muscle concentrations of His but had minor or no effects on other production variables in dairy cows.

Milk production and efficiency of utilization of nitrogen, metabolizable protein, and amino acids are affected by protein and energy supplies in dairy cows fed alfalfa-based diets

Alfalfa has a lower fiber digestibility and a greater concentration of degradable protein than grasses. Dairy cows could benefit from an increased digestibility of alfalfa fibers, or from a better match between nitrogen and energy supplies in the rumen. Alfalfa cultivars with improved fiber digestibility represent an opportunity to increase milk production, but no independent studies have tested these cultivars under the agroclimatic conditions of Canada. Moreover, decreasing metabolizable protein (MP) supply could increase N use efficiency while decreasing environmental impact, but it is often associated with a decrease in milk protein yield, possibly caused by a reduced supply of essential AA. This study evaluated the performance of dairy cows fed diets based on a regular or a reduced-lignin alfalfa cultivar and measured the effect of energy levels at low MP supply when digestible His (dHis), Lys (dLys), and Met (dMet) requirements were met. Eight Holstein cows were used in a double 4 × 4 Latin square design, each square representing an alfalfa cultivar. Within each square, 4 diets were tested: the control diet was formulated for an adequate supply of MP and energy (AMP_AE), whereas the 3 other diets were formulated to be deficient in MP (DMP; formulated to meet 90% of the MP requirement) with deficient (94% of requirement: DMP_DE), adequate (99% of requirement: DMP_AE), or excess energy supply (104% of requirement; DMP_EE). Alfalfa cultivars had no significant effect on all measured parameters. As compared with cows receiving AMP_AE, the dry matter intake of cows fed DMP_AE and DMP_EE was not significantly different but decreased for cows fed DMP_DE. The AMP_AE diet provided 103% of MP and 108% of NE_L requirements whereas DMP_DE, DMP_AE, and DMP_EE diets provided 84, 87, and 87% of MP and 94, 101, and 107% of NE_L requirements, respectively. In contrast to design, feeding DMP_EE resulted in a similar energy supply compared with AMP_AE, although MP supply has been effectively reduced. This resulted in a maintained milk and milk component yields and improved the efficiency of utilization of N, MP, and essential AA. The DMP diets decreased total N excretion, whereas DMP_AE and DMP_EE diets also decreased milk urea-N concentration. Reducing MP supply without negative effects on dairy cow performance is possible when energy, dHis, dLys, and dMet requirements are met. This could reduce N excretion and decrease the environmental impact of milk production.

Low-protein diets supplemented with methionine and lysine alter the gut microbiota composition and improve the immune status of growing lambs

Feeding low-protein (LP) diets with essential amino acids could be an effective strategy for ruminants from economic, health and environmental perspectives. This study was conducted to investigate the effects of rumen-protected methionine and lysine (RML) in the LP diet on growth performance, innate immunity, and gut health of growing lambs. After 15 days of adaption, sixty-three male Hulunbuir lambs aged approximately 4 months were allotted to three dietary groups and each group had three pens with seven lambs for 60 days. The dietary treatments were as follows: a normal protein diet (14.5% CP, positive control; NP), LP diet (12.5% CP, negative control; LP), and LP diet with RML (12.5% CP, LP + RML). Lambs fed with LP + RML diet showed improved villus architecture and gut barrier function than those fed with the other two diets. The mRNA expressions of interleukin-1β, tumor necrosis factor-α, interferon-γ, toll-like receptor-4, and myeloid differentiation primary response 88 were downregulated in most regions of the intestinal segments by feeding the LP + RML diet. Compared with the NP diet, feeding lambs with the LP diet increased the abundance of Candidatus_Saccharimonas in all regions of the intestinal tract and reversed by feeding the LP + RML diet. Lambs in the LP + RML diet group had lower abundance of Erysipelotrichaceae_UCG-009 and Clostridium_sensu_stricto_1 than those in the LP diet group. The results showed that supplementing RML in the LP diet exhibited beneficial effects on host immune function, intestinal mucosal integrity, and microbiota composition. KEY POINTS: • Adding methionine and lysine in a low-protein diet improve the intestinal mucosal growth and integrity. • Feeding a low-protein diet with methionine and lysine enhance the innate immune status. • Adding methionine and lysine in a low-protein diet alter the intestinal microbiota composition.

Effects of supplementing a CP-reduced diet with rumen-protected methionine on Fleckvieh bull fattening

The objective of this study was to evaluate the effect of supplementing a CP-reduced diet with rumen-protected methionine on growth performance of Fleckvieh bulls. A total of 69 bulls (367 ± 25 kg BW) were assigned to three feeding groups (n = 23 per group). The control (CON) diet contained 13.7% CP and 2.11 g methionine/kg diet (both DM basis) and was set as positive control. The diet reduced in CP (nitrogen) (RED) diet as negative control and the experimental RED + rumen-protected methionine (MET) diet were characterised by deficient CP concentrations (both 9.04% CP). The RED + MET diet differed from the RED diet in methionine concentration (2.54 g/kg DM vs. 1.56 g/kg DM, respectively) due to supplementation of rumen-protected methionine. Rumen-protected lysine was added to both RED and RED + MET at 2.7 g/kg DM to ensure a sufficient lysine supply relative to total and metabolisable protein intake. Metabolisable energy (ME) and nutrient composition were similar for CON, RED, and RED + MET. Bulls were fed for 105 days (d) on average. Individual feed intake was recorded daily; individual BW was recorded at the beginning of the experiment, once per month, and directly before slaughter. At slaughter, blood samples were collected and carcass traits were assessed. Reduction in dietary CP concentration reduced feed intake, and in combination with lower dietary CP concentration, daily intake of CP for RED and RED + MET was lower compared with CON (P < 0.01). Daily ME intake was reduced in RED and RED + MET compared with CON (P < 0.01). Consequently growth performance and carcass weights were reduced (both P < 0.01) in both RED and RED + MET compared with CON. Supplemental rumen-protected methionine was reflected in increased serum methionine concentration in RED + MET (P < 0.05) as compared to RED but it did not affect growth performance, carcass traits and serum amino acid (AA) concentrations, except for lysine which was reduced (P < 0.01) compared to CON and RED. In conclusion, bulls fed RED or RED + MET diets were exposed to a ruminal CP deficit and subsequently a deficit of prececal digestible protein, but methionine did not appear to be the first-limiting essential AA for growth under the respective experimental conditions.