Temporal and interanimal variation in bloodspot acylcarnitine and amino acid profiles in relation to conventional metabolites and hormones in Holstein dairy cows

The transition from late gestation to early lactation in dairy cows involves dynamic metabolic adaptations orchestrated by homeorhetic mechanisms, including hepatic fatty acid and AA metabolism. To gain deeper understanding of these mechanisms, we evaluated changes in bloodspot acylcarnitines (AC) and free AA profiles, and conventional blood biomarkers of energy balance (BHB, nonesterified fatty acids [NEFA], glucose, insulin, IGF-1, and fructosamine) along with weekly milk composition and DMI in 2 sequential observational trials. Data were analyzed using correlation and cluster analysis, and linear mixed-effects models with and without repeated measures. Study 1, which involved 28 multiparous Holstein-Friesian cows sampled 7 d before calving and at 3, 6, 9 and 21 d after calving, revealed strong positive correlations between glycine-to-alanine ratio with BHB (r = 0.58) and NEFA (r = 0.59), though these correlations weakened in study 2. Four trajectory patterns in AC, AA, and metabolite ratios were identified. Group 1 (e.g., C5, C16, and C18) showed transient postpartum increase peaking by d 3 or 6, returning to prepartum levels by d 21. Group 2 (e.g., tyrosine, C0:(C16 + C18) exhibited transient postpartum decrease, normalizing by d 21. Group 3 (e.g., C4DC:C3, t[AC]:C0, and valine-to-phenylalanine ratio) displayed variable postpartum responses, whereas group 4 exhibited persistent differences at d 21, with elevated glycine-to-alanine and valine-to-leucine ratios but reduced methionine and ornithine-to-citrulline ratio compared with prepartum levels. Study 2, which examined intercow variations and comprised of 74 cows (83 lactations) sampled at 21 DIM, revealed 2 distinct clusters of clinically healthy cows based on longitudinal time serum BHB profiles: normal and high milk yield-hyperketonemia (HMY-HYK). The HMY-HYK cows had higher milk yield (41.6 ± 1.05 vs. 39.4 ± 0.767 kg/d), average serum BHB and NEFA (0.996 ± 0.086 vs. 0.754 ± 0.062 mmol/L and 0.498 ± 0.051 vs. 0.534 ± 0.071 mmol/L, respectively) and lower insulin (0.343 ± 0.030 vs. 0.368 ± 0.041ng/mL) compared with cows in the normal cluster. The higher milk yield, increased milk urea concentrations, and reduced bloodspot citrulline levels in the HMY-HYK cows suggest enhanced AA catabolism for gluconeogenesis and reduced activity in the ornithine-citrulline cycle. Elevated bloodspot malonylcarnitine, long-chain AC (LCAC) with C16 and C18 carbon chains, acetylcarnitine-to-free carnitine (C2:C0) ratio but lower free carnitine (C0) levels indicate efficient mitochondrial responses, potentially exporting acyl-CoA as C2 and LCAC to mitigate metabolic stress associated with elevated NEFA. In conclusion, bloodspot AC, AA, and metabolite ratios highlight time-dependent and interanimal shifts in adipose and muscle mobilization, as well as adaptive mitochondrial metabolism of NEFA and AA catabolism to support gluconeogenesis and thus, milk synthesis in early lactation.

Effects of monensin and essential oil blend supplementation on lactation performance and feeding behavior in dairy cows

The objective of this study was to evaluate the effects of supplementation with an essential oil blend (0.16 g/kg DM of carvacrol, eugenol, thymol, and capsaicin) and monensin (17.6 mg/kg DM TMR) on lactation performance, feeding behavior, and rumen fermentation in high-producing dairy cows. Sixty-four multiparous Holstein cows (89 ± 21 DIM and 729 ± 68 kg of BW at covariate period initiation), including 16 cannulated cows, and 32 gate feeders were enrolled in a study with a completely randomized design and a 2 × 2 factorial arrangement. Cows and gate feeders were randomly assigned to treatments (4 cannulated cows and 12 cows not cannulated, for a total of 16 cows, and 8 gate feeders per treatment). Cows were allowed 1 wk to acclimate to gate feeders followed by a 2-wk covariate period. During the acclimation and covariate periods, all cows were fed a diet containing the essential oil blend and monensin. Following the covariate period, cows were enrolled in a 10-wk treatment period during which cows were randomly assigned to 1 of 4 treatments: (1) a combination of the essential oil blend and monensin (EOB-MON), (2) the essential oil blend alone (EOB), (3) monensin alone (MON), or (4) neither the essential oil blend nor monensin (CON). Data were analyzed using a mixed model with week as a repeated measure and essential oil blend, monensin, week, and all their interactions as fixed effects. Cow (treatment) was included as a random effect. The average covariate period value of each variable was used as a covariate. A 3-way interaction was observed for DMI, where DMI was lowest for CON and MON in wk 1 but then was lowest for EOB in wk 4, 9, and 10. Supplementing the essential oil blend also decreased BW during wk 4 and 10 and tended to decrease BW change but increased the maximum pH in the rumen. Monensin tended to improve milk production and lactose yield but decreased milk fat concentration without affecting milk fat yield. Thus, feeding monensin appears to improve milk yield but maintain or increase component yields. However, feeding dairy cows a combination of carvacrol, eugenol, thymol, and capsaicin decreased DMI for 3 out of 10 wk at the expense of BW gain.

Daily Gain, Feed Conversion, and Rumen Fermentation in Finishing Steers Fed a Total Mixed Ration Supplemented with a Blend of Essential Oils, Tannins, and Bioflavonoids or Monensin

This study investigated the effects of adding a blend of essential oils, tannins, bioflavonoids (ANAVRIN®, VetosEurope, Lugano, Switzerland), monensin, and their combination on the daily gain, feed conversion, and rumen fermentation of finishing steers fed a total mixed ration (TMR). Thirty finishing steers (441 kg body weight, 34.3 months old) consuming a TMR were blocked by BW and randomly assigned to three treatments according to the addition of (1) EOTB (ANAVRIN® at 0.35 g/100 kg body weight), (2) MON (monensin at 0.033 g/kg dry matter), and (3) EOTB + MON (at the same dose as in (1) and (2). A 60-day feeding trial was conducted, including a 19-day adaptation period. Data collected included daily dry matter intake (DMI), average daily gain (ADG), feed conversion ratio (FCR), and rumen fermentation parameters (pH, NH3-N, and volatile fatty acid (VFA) concentrations). EOTB resulted in higher DMI compared to EOTB + MON, while no significant differences were observed in ADG or FCR. The ruminal pH and NH3-N concentrations were similar among treatments, but there were interactions among treatment × hour for VFAs. The EOTB + MON led to a more stable VFA concentration in rumen, suggesting possible complementary supplementation effects. However, more studies are needed to confirm this and to go deeper into the underlying mechanism of action.

Effect of monensin and live-cell yeast supplementation on lactation performance, feeding behavior, and total-tract nutrient digestibility in dairy cows

The objective of this study was to evaluate the effects of supplementing monensin (19.8 g/Mg DM TMR; MON) and Saccharomyces cerevisiae CNCM I-1077 live-cell yeasts (Saccharomyces cerevisiae CNCM I-1077; 1 × 1010 cfu/head per day; LCY) on lactation performance, feeding behavior, and total-tract nutrient digestibility of high-producing dairy cows. Sixty-four multiparous Holstein cows (3.2 ± 1.5 lactations; 97 ± 16 DIM, and 724 ± 68 kg of BW at covariate period initiation) and 32 gate feeders were enrolled in a study with a completely randomized design and a 2 × 2 factorial arrangement. Cows and gate feeders were randomly assigned to treatments (16 cows and 8 gate feeders per treatment). Cows were allowed 2 wk to acclimate to feeding gates followed by a 2-wk covariate period. During the acclimation and covariate periods, all cows were fed a diet containing MON and LCY. Following the covariate period, cows were enrolled in a 10-wk treatment period during which cows were randomly assigned to 1 of 4 treatments: (1) a combination of MON and LCY (MON-LCY), (2) MON-CON, (3) CON-LCY, or (4) neither MON nor LCY (CON-CON). Data were analyzed using a mixed model with week as a repeated measure and fixed effects of MON, LCY, week, and all their interactions. Cow (treatment) was included as a random effect. The average covariate period value of each variable was used as a covariate. Three-way interactions were observed for DMI and feed efficiency. Dry matter intake decreased from wk 4 to 5 and wk 8 to 10 in MON-LCY cows compared with CON-CON. No treatment differences were observed for actual or component-corrected milk yield or milk components, except for a tendency for LCY to decrease milk fat yield. Feed efficiency was greater for MON-LCY relative to CON-CON in 4 of 10 wk. Interactions between MON and LCY were observed for dry matter and organic matter digestibility, where both were lower for CON-CON than other treatments. Under the conditions of the present study, feeding dairy cows in a high feed bunk density a combination of MON and LCY can decrease intake and improve feed efficiency without affecting milk production or components. Additionally, monensin and live-cell yeasts may each improve total-tract digestibility based on improvements in DM and OM digestibility.

Effect of monensin on milk production efficiency and milk composition in lactating dairy cows fed modern diets

Since the US Food and Drug Administration's approval of monensin in 2004, significant nutritional advances have been made to increase feed efficiency and milk fat production. Recent evidence suggests monensin's adverse effect on milk fat percentage may be absent when diets are formulated to address known diet-induced milk fat depression risk factors. Thus, study objectives were to evaluate effects of monensin level on dry matter intake (DMI), milk production and composition, and efficiency of high-producing cows fed diets formulated to optimize milk fat. Ninety-six lactating Holstein cows (36 primiparous, 60 multiparous; 106 ± 17 d in milk [DIM]) were balanced by parity, DIM, and milk production and were randomly assigned to 1 of 12 pens with 8 cows per pen. All cows received 11 g/t monensin for 5 wk after which pens received 1 of 4 dietary treatments (n = 3) formulated to provide 0 (CON), 11 (R11), 14.5 (R14.5), or 18 (R18) g/t monensin for 9 wk. The basal diet was 54% forage, 27% NDF, 29% starch, and 2.3% rumen unsaturated fatty acid load. Pen was the experimental unit and data were analyzed using the Fit Model Procedure of JMP. Effects of treatment, time, and treatment × time interaction were included as fixed effects and pen as a random effect. Least squares means were determined and linear and quadratic contrasts were tested. Dry matter intake tended to decrease linearly with increasing monensin dose. Milk yield, fat percentage, and protein percentage and yield were unaffected by treatment while fat yield was quadratically increased. Milk de novo and mixed fatty acid (FA) yields (g/d) increased quadratically with monensin whereas preformed FA linearly decreased during the experimental period. Energy-corrected milk (ECM) was quadratically increased by monensin. Milk urea nitrogen concentrations increased linearly with increasing monensin dose. Monensin linearly increased feed efficiency (ECM/DMI, 3.5% fat-corrected milk/DMI, and solids-corrected milk/DMI). Body weight gain did not differ between treatments. Estimated dietary energy tended to increase linearly with increasing monensin level. These data suggest monensin improves component-corrected milk production efficiency, estimated dietary energy, and does not negatively affect milk fat percentage or FA profile.

Effects of cashew nut shell extract and monensin on in vitro ruminal fermentation, methane production, and ruminal bacterial community

The objective of this study was to evaluate the effects of cashew nut shell extract (CNSE) and monensin on ruminal in vitro fermentation, CH4 production, and ruminal bacterial community structure. Treatments were as follows: control (CON, basal diet without additives); 2.5 μM monensin (MON); 0.1 mg CNSE granule/g DM (CNSE100); and 0.2 mg CNSE granule/g DM (CNSE200). Each treatment was incubated with 52 mL of buffered ruminal content and 500 mg of total mixed ration for 24 h using serum vials. The experiment was performed as a complete randomized block design with 3 runs. Run was used as a blocking factor. Each treatment had 5 replicates, in which 2 were used to determine nutrient degradability, and 3 were used to determine pH, NH3-N, volatile fatty acids, lactate, total gas, CH4 production, and bacterial community composition. Treatment responses for all data, excluding bacterial abundance, were analyzed with the GLIMMIX procedure of SAS v9.4. Treatment responses for bacterial community structure were analyzed with a PERMANOVA test run with the R package vegan. Orthogonal contrasts were used to test the effects of (1) additive inclusion (ADD: CON vs. MON, CNSE100, and CNSE200); (2) additive type (MCN: MON vs. CNSE100 and CNSE200); and (3) CNSE dose (DOS: CNSE100 vs. CNSE200). We observed that pH, acetate, and acetate:propionate ratio in the CNSE100 treatment were lower compared with CNSE200, and propionate in the CNSE100 treatment was greater compared with CNSE200. Compared with MON, CNSE treatments tended to decrease total lactate concentration. Total gas production of CON was greater by 2.63% compared with all treatments, and total CH4 production was reduced by 10.64% in both CNSE treatments compared with MON. Also, compared with MON, in vitro dry matter degradabilities in CNSE treatments were lower. No effects were observed for NH3-N or in vitro neutral detergent fiber degradability. Finally, the relative abundances of Prevotella, Treponema, and Schwartzia were lower, whereas the relative abundances of Butyrivibrio and Succinivibrio were greater in all treatments compared with CON. Overall, the inclusion of CNSE decreased CH4 production compared with MON, making CNSE a possible CH4 mitigation additive in dairy cattle diets.

Effects of monensin supplementation on rumen fermentation, methane emissions, nitrogen balance, and metabolic responses of dairy cows: A systematic review and dose-response meta-analysis

To investigate the effects of supplemental monensin administration on the metabolic responses of dairy cows, a systematic review and dose-response meta-analysis were conducted. Initially, 604 studies were identified through comprehensive database searches, including Google Scholar, Scopus, Science Direct, and PubMed, using key words related to dairy cows, monensin, and metabolic outcomes. After a 2-stage screening process, 51 articles with a total of 60 experiments were selected for meta-analysis based on criteria such as study implementation date between 2001 and 2022, presence of a control group that did not receive monensin supplementation, reporting of at least 1 outcome variable, and presentation of means and corresponding errors. The meta-analysis used the 1-stage random-effects method, and sensitivity analyses were performed to assess the robustness of the results. The results showed that the administration of monensin at a dosage of 19 to 26 mg/kg was inversely related to methane emissions and that the administration of monensin at a dosage of 18 to 50 mg/kg resulted in a significant decrease in dry matter intake. Administration of monensin at doses of 13 to 28 and 15 to 24 mg/kg also resulted in a significant decrease in ruminal acetate proportion and an increase in propionate proportion, respectively, with no effects on ruminal butyrate, NH3, or pH levels. We found no effects on blood parameters or nitrogen retention, but a significant negative correlation was observed between monensin supplementation and fecal nitrogen excretion. Based on the analysis of all variables evaluated, the optimal dose range of monensin was estimated to be 19 to 24 mg/kg.

[The lipidosis in the liver of the dairy cow: Part 2 Genetic predisposition and prophylaxis]

Hepatic lipidosis in dairy cows is the result of a disturbed balance between the uptake of non-esterified fatty acids (NEFA), their metabolism in the hepatocytes, and the limited efflux of TG as very-low-density lipoprotein (VLDL). Lipidosis and the associated risk for ketosis represents a consequence of selecting dairy cows primarily for milk production without considering the basic physiological mechanisms of this trait. The overall risk for lipidosis and ketosis possesses a genetic background and the recently released new breeding value of the German Holstein Friesian cows now sets the path for correction of this risk and in that confirms the assumed genetic threat. Ectopic fat deposition in the liver is the result of various steps including lipolysis, uptake of fat by the liver cell, its metabolism, and finally release as very-low-density lipoprotein (VLDL). These reactions may be modulated directly or indirectly and hence, serve as basis for prophylactic measures. The pertaining methods are described in order to support an improved understanding of the pathogenesis of lipidosis and ketosis. They consist of feeding a glucogenic diet, restricted feeding during the close-up time as well as supplementation with choline, niacin, carnitine, or the reduction of milking frequency. Prophylactic measures for the prevention of ketosis are also included in this discussion.

Essential Oils Combined with Vitamin D3 or with Probiotic as an Alternative to the Ionophore Monensin Supplemented in High-Energy Diets for Lambs Long-Term Finished under Subtropical Climate

Supplementation with natural additives such as essential oils (EO) or probiotics has resulted in comparable growth performance to that of supplemental monensin in fattening lambs in hot environments. Supra-supplementation levels of vitamin D3 improved the carcass weight and dressing percentage of steers fattened under tropical conditions. We hypothesized that certain combinations of these natural additives could be complementary. For this reason, a feeding trial was carried out using 48 Pelibuey × Katahdin non-castrated male lambs (107 ± 14 d age; 17.9 ± 2.51 kg LW). Lambs were fed an 88:12 concentrate to forage ratio basal diet supplemented (dry matter basis, DMI) with: (1) no additive (CON); (2) 28 mg monensin/kg diet (MON); (3) 150 mg of essential oils containing a combination of thymol, eugenol, vanillin, guaiac, and limonene plus 0.12 mg vitamin D3 (EO + D3)/kg diet; and (4) 300 mg of essential oils containing a combination of carvacrol and cynamaldehyde plus 2 g probiotic (2.2 × 108 CFU of bacillus subtilis/kg diet, EO + BS). Lambs were grouped by initial weight and assigned within six weight groupings to 24 pens (2 lambs/pen, 6 replicas per treatment) in a randomized complete block design. The experiment lasted 121 days. Daily maximal THI exceeded the 80 "danger or "emergency" range for 119 days of the 121 days of the trial. Lambs supplemented with MON had similar DMI, growth performance, and dietary energetics to those of CON lambs. Lambs supplemented with EO + BS had a greater (9.2%, p ≤ 0.05) average daily gain (ADG) than the CON and MON groups due to enhanced (10.2%, p ≤ 0.05) dry matter intake. Thus, gain efficiency (GF) and estimated dietary energy were similar for CON, MON, and EO + BS. Lambs receiving EO + D3 had similar (0.254 vs. 0.262 kg/d) ADG but a lower DMI (8%, p < 0.05) compared with EO + BS lambs. Consequently, GF and estimated dietary net energy were greater (4.9 and 3.7%, respectively; p ≤ 0.05) for EO + D3 lambs. Even when ambient heat load was elevated, the efficiency of utilization of dietary energy (observed-to-expected dietary net energy) was close to 1.00 (0.992) expected for EO + D3 lambs. In contrast, efficiency of energy utilization was depressed by -4.4% for lambs on the other treatments. Compared with the other treatments, lambs receiving EO + D3 had greater longissimus muscle area (5.6%, p < 0.05) and lower kidney pelvic fat (21.8%, p ≤ 0.05). There were no treatment effects on shoulder tissue composition or whole cuts (expressed as % of cold carcass weight). Compared to CON, lambs that were fed with natural additives showed 3.5% lower (p ≤ 0.05) intestine mass. All supplemental additives decreased visceral fat mass, which was minimal with EO + D3 treatment. Combinations of essential oils with vitamins or probiotics were superior to antibiotic monensin in finishing diets for feedlot lambs. Combining EO with probiotics promoted DM intake and gain but not gain efficiency, while combining EO with vitamin D3 supra-supplementation increased dietary energy efficiency and improved some carcass characteristics in lambs fattening under high ambient heat loads.

The effect of propolis extract on milk production and composition, serum biochemistry, and physiological parameters of heat-stressed dairy cows

The aim of this study was to evaluate whether feeding propolis extract (PE) influences nutrient intake, milk production and composition, serum biochemistry, and physiological parameters of heat-stressed dairy cows. For this purpose, we used three primiparous Holstein cows with a lactation period of 94 ± 4 days and with 485 ± 13 kg body weight. The treatments were 0 mL/day, 32 mL/day, and 64 mL/day of PE randomly assigned in a 3x3 Latin square design, repeated over time. The experiment lasted a total of 102 days; each Latin square lasted 51 days divided into three 17-day periods (12 days for adaptation and five days for data collection). The PE supply did not influence (P > 0.05) the cows' intake of dry matter (18.96 kg/d), crude protein (2.83 kg/d), and neutral detergent-insoluble fiber (7.36 kg/d), but there was an increase in feeding time with the 64 ml/day PE supply (P < 0.05). Providing 64 ml/day of PE tended (P = 0.06) to increase milk production by 11.64% and improve gross feed efficiency of cows by 12.04%. The PE supply did not influence milk composition and blood parameters of cows (P > 0.05). Offering 32 mL/day of PE decreased (P < 0.05) the rectal temperature and respiratory rate of cows. We recommend a supply of 64 mL/day of PE for heat-stressed dairy cows.

M-Mode Echocardiographic Measurements of Interventricular Septum, Left Ventricular Internal Diameter, and Left Ventricular Free-Wall Thickness in Normal Horses-A Meta-Analytical Study

The purpose of this study was to provide a systematic meta-analysis on echocardiographic measurements in normal Thoroughbred and Standardbred horses. The current systematic meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). All the available published papers on the reference values of echocardiographic assessment via M-mode echocardiography were searched, and fifteen studies were finally selected for analysis. In both fixed and random effect, the confidence interval (CI) for the interventricular septum (IVS) was 2.8-3.1 and 4.7-7.5; for the left ventricular free-wall (LVFW) thickness, it was 2.9-3.2 and 4.2-6.7; and for the left ventricular internal diameter (LVID), it was -5.0-4.6 and -10.0--6.7, respectively. For IVS, the Q statistic, I-squared, and tau-squared were 925.3, 98.1, and 7.9, respectively. Similarly, for LVFW, all the effects were on the positive side of zero, with a range of 1.3-68.1. The CI indicated a significant variation among the studies (fixed, 2.9-3.2; random, 4.2-6.7). The z-values of LVFW for fixed and random effects were, respectively, 41.1 (p < 0.001) and 8.5 (p < 0.001). However, the Q statistic was 886.6 (p < 0.001). Moreover, the I-squared was 98.08, and the tau-squared was 6.6. By contrast, the effects of LVID fell on the negative side of zero, (2.8-83.9). The present meta-analysis provides an overview of the echocardiographic measurements of cardiac diameters in healthy Thoroughbred and Standardbred horses. The meta-analysis indicates variations in results among different studies. This result should be considered when evaluating a horse for heart disease and each case should be evaluated independently.

Association of herd hyperketolactia prevalence with transition management practices and herd productivity on Canadian dairy farms-A retrospective cross-sectional study

The objective of this observational study was to assess the relationship between herd-level prevalence of hyperketolactia (HPH) with management practices of the transition period and herd milk production. Dairy herds (n = 71) were selected based on their inclusion in a herd management risk assessment study (August 2014-March 2018) using a Vital 90 (Elanco) Risk Assessment tool (one assessment per farm). Data from multiple milk recording test-days (Dairy Herd Improvement, DHI; Lactanet) were included in the analysis. Tests performed within ±6 mo relative to each farm's risk assessment date were included (10 ± 2 SD tests per farm). The majority of the farms were located in Ontario (83%). For each farm DHI test, the data set included herd average milk yield (kg/cow per day), average milk fat and protein (%), average somatic cell count (cells/mL), average days in milk (DIM), number of cows tested for ketosis, number of ketosis-positive tests (milk β-hydroxybutyrate ≥0.15 mmol/L), and proportion of cows by parity groups. Overall HPH (5-21 DIM) was calculated based on data available per farm (sum of all positive tests within 5-21 DIM/sum of all cows tested within 5-21 DIM). Each farm average was obtained by considering all test-days. A logit-transformation was applied to hyperketolactia prevalence. Linear regression models (PROC GLM and MIXED of SAS, Version 9.4) were used to predict herd HPH (milk β-hydroxybutyrate ≥0.15 mmol/L within 5 to 21 DIM; the outcome of interest). Four initial models (far-off, close-up, and fresh periods, and DHI) were separately built to assess associations between their variables and HPH; a final model considered variables selected in the initial models. Univariable (liberal P < 0.25) followed by multivariable models were used to build specific models for each period of the risk assessment. Herd prevalence of hyperketolactia was 27 ± 14%, with an average herd size of 141 ± 110 cows. The final HPH model (R² = 24.8%) included weighted milk yield, the proportion of primiparous cows, water access in the close-up period, and access to rest areas or stall access in the fresh period. Herd prevalence of hyperketolactia was negatively associated with milk yield [odds ratio, OR = 0.96 (95% confidence interval 0.92-0.99)] and proportion of primiparous cows [OR = 0.98 (0.96-0.99)]. The odds of hyperketolactia were greater with poor water access and quality (<5 cm of linear access per cow; dirty water; only 1 water location in pen) than with ≥10.2 cm of linear access per cow; clean water; >2 water locations in pen [1.23 (1.11-2.39)] in the close-up period. The odds of hyperketolactia were greater in farms providing limited access to rest areas in the fresh period than in farms providing constant access to rest areas, without dead-ends [1.64 (1.03-2.80)]. In Canadian dairy herds, HPH in early lactation was associated with certain transition-period management practices and was negatively associated with herd productivity.

Animal board invited review: The contribution of adipose stores to milk fat: implications on optimal nutritional strategies to increase milk fat synthesis in dairy cows

A wide range of nutritional and non-nutritional factors influence milk fat synthesis and explain the large variation observed in dairy herds. The capacity of the animal to synthesize milk fat will largely depend on the availability of substrates for lipid synthesis, some of which originate directly from the diet, ruminal fermentation or from adipose tissue stores. The mobilization of non-esterified fatty acids from adipose tissues is important to support the energy demands of milk synthesis and will therefore have an impact on the composition of milk lipids, especially during the early lactation period. Such mobilization is tightly controlled by insulin and catecholamines, and in turn, can be affected indirectly by factors that influence these signals, namely diet composition, lactation stage, genetics, endotoxemia, and inflammation. Environmental factors, such as heat stress, also impact adipose tissue mobilization and milk fat synthesis, mainly through endotoxemia and an immune response-related increase in concentrations of plasma insulin. Indeed, as proposed in the present review, the central role of insulin in the control of lipolysis is key to improving our understanding of how nutritional and non-nutritional factors impact milk fat synthesis. This is particularly the case during early lactation, as well as in situations where mammary lipid synthesis is more dependent on adipose-derived fatty acids.

Effects of monensin supplementation on lactation performance of dairy cows: a systematic review and dose-response meta‑analysis

The aim of this study was to conduct a comprehensive review with meta-analysis to determine the effects of the dose-response relationship between monensin supplementation and dairy cow performance and milk composition. Results from 566 full-text articles and 48 articles with 52 studies were meta-analyzed for pooled estimates. Monensin supplementation up to 23 ppm increased milk production, with the optimal dose being 12.6 ppm. Monensin supplementation at doses ranging from 16 to 96 ppm increased milk production in the prepartum phase (- 28 to 0 day relative to calving). From 60 to 150 DIM, monensin supplementation up to 21 ppm had a significant positive effect on this outcome, while supplementation in the 37 to 96 ppm range caused a decrease in this variable. At 0 to 60 and > 150 DIM, monensin supplementation had no effect on milk yield. At dosages of 22 to 96 ppm, 12 to 36 ppm, and below 58 ppm and 35 ppm, respectively, monensin supplementation resulted in significant decreases in dry matter intake (DMI), milk protein percentage, milk fat percentage, and milk fat yield. Overall, based on the results of this meta-analysis and considering all variables, the recommended optimal dose of monensin could be about 16 ppm.

The impact of environmental and nutritional stresses on milk fat synthesis in dairy cows

Stress reduces milk and milk components synthesis and increases maintenance requirements of cows. The major stress-related alterations involve enhanced secretion of glucocorticoids and increased sympathetic nervous system activity, which results in biochemical and physiologic changes. In dairy cows exposed to social (ie housing conditions, overstocking, regrouping, feed delivery), physiological (ie initiation of lactation and parturition), or physical (ie heat or cold stress) stressors, responses involve alterations in energy balance and nutrient partitioning. The capacity of the animal to synthesize milk fat largely depends on the availability of substrates for lipid synthesis from the diet, ruminal fermentation or adipose tissue stores, all of which can be altered under stress conditions. Indeed, milk fat concentration is particularly responsive to diet and environment modifications, where a wide range of nutritional and non-nutritional factors influence milk fat output. Milk fat synthesis is an energy demanding process, and extremely sensitive to stress factors during lactation and the involvement of multiple organs. Recent studies examining social, physical, and physiological stressors have provided important insights into how differences in milk yield and milk components may be associated with biological responses to stress factors in dairy cows. This review focuses primarily on the role of stress sources and indicators to which the dairy cow is exposed in regulating milk fat synthesis. We will review the role of nutritional and non-nutritional factors on milk fat synthesis in dairy cows under stress conditions.

Supplementation of Ascophyllum nodosum meal and monensin: Effects on diversity and relative abundance of ruminal bacterial taxa and the metabolism of iodine and arsenic in lactating dairy cows

Previous research has shown that the brown seaweed Ascophyllum nodosum (ASCO) has antimicrobial and antioxidant properties and also increases milk I concentration. We aimed to investigate the effects of supplementing ASCO meal or monensin (MON) on ruminal fermentation, diversity and relative abundance of ruminal bacterial taxa, metabolism of I and As, and blood concentrations of thyroid hormones, antioxidant enzymes, and cortisol in lactating dairy cows. Five multiparous ruminally cannulated Jersey cows averaging (mean ± standard deviation) 102 ± 15 d in milk and 450 ± 33 kg of body weight at the beginning of the study were used in a Latin square design with 28-d periods (21 d for diet adaptation and 7 d for data and sample collection). Cows were fed ad libitum a basal diet containing (dry matter basis) 65% forage as haylage and corn silage and 35% concentrate and were randomly assigned to 1 of the following 5 dietary treatments: 0, 57, 113, or 170 g/d of ASCO meal, or 300 mg/d of MON. Supplements were placed directly into the rumen once daily after the morning feeding. Diets had no effect on ruminal pH and NH3-N concentration, which averaged 6.02 and 6.86 mg/dL, respectively. Total volatile fatty acid concentration decreased linearly in cows fed incremental amounts of ASCO meal. Supplementation with ASCO meal did not change the ruminal molar proportions of volatile fatty acids apart from butyrate, which responded quadratically with the lowest values observed at 56 and 113 g/d of ASCO supplementation. Compared with the control diet or diets containing ASCO meal, cows fed MON showed greater molar proportion of propionate. Diets did not affect the α diversity indices Shannon, Simpson, and Fisher for ruminal bacteria. However, feeding incremental levels of ASCO meal linearly decreased the relative abundance of Tenericutes in ruminal fluid. Monensin increased the relative abundance of the CAG:352 bacterial genus in ruminal fluid compared with the control diet. Linear increases in response to ASCO meal supplementation were observed for the concentrations and output of I in serum, milk, urine, and feces. Fecal excretion of As increased linearly in cows fed varying amounts of ASCO meal, but ASCO did not affect the concentration and secretion of As in milk. The plasma activities of the antioxidant enzymes and the serum concentrations of thyroid hormones did not change. In contrast, circulating cortisol decreased linearly in diets containing ASCO meal. The apparent total-tract digestibilities of dry matter, organic matter, and crude protein increased linearly with ASCO meal, but those of neutral and acid detergent fiber were not affected. In summary, feeding incremental amounts of ASCO meal decreased serum cortisol concentration, and increased I concentrations and output in serum, milk, feces, and urine.

Monensin supplementation downregulated the expression signature of genes involved in cholesterol synthesis in the ruminal epithelium and adipose tissue of lambs

To understand the metabolic mechanisms regulating lipid metabolism by monensin, Afshari male lambs (n = 16) with 41.0 ± 2.4 kg body weight (BW, mean ± SD) at approximately 180 days of age were randomly assigned equally to two dietary treatments. After a 21-day pre-adaptation period, all animals in two groups continued to receive the basal diet, but one group received no monensin supplementation (control) while the other group received 30 mg/day of monensin per animal. Individual BW was recorded weekly to determine the average daily body weight gain (ADG). At the end of the 56-day experimental period, lambs were weighed and slaughtered. Monensin supplementation did not affect BW, ADG, and rumen fermentation characteristics. However, monensin significantly downregulated the sterol regulatory element-binding protein (SREBP)-2 gene expression in all sample tissues (p < 0.05). Also, monensin downregulated expressions of SREBP-1c and peroxisome proliferator-activated receptor (PPAR)-γ in back fat tissues. Monensin increased the expression of 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS)-2, but it decreased the mRNA abundance of HMGCS-1 in the rumen epithelial tissues (p < 0.05). Our data suggest that monensin downregulates cholesterol synthesis via inhibition of HMGCS-1 and impairment of the SREBP pathway, probably due to a crosstalk among different tissues to control energy metabolism.

Effects of Ionophores on Ruminal Function of Beef Cattle

Ionophores have been widely used in the beef and dairy industry for decades to improve feed efficiency and performance by altering ruminal fermentation dynamics, increasing the level of propionate. Ionophores can also reduce ruminal proteolysis and ammonia synthesis, thus increasing the influx of protein into the small intestine in cattle, leading to improvements in performance and efficiency responses. Ionophores indirectly impact ruminal methanogenesis by decreasing the substrate used to produce methane. Despite the consistent benefits of using ionophores in cattle nutrition, their utilization is under public scrutiny due to concerns related to microbial adaptation. However, there is inconsistent evidence supporting these concerns, whereas ionophores are still an important dietary tool to enhance productivity and profitability in beef production systems.

Nutrient digetibility and production responses of lactating dairy cows when saturated free fatty acid supplements are included in diets: A meta-analysis

Our objective was to perform a series of meta-analyses to evaluate the effects of diets supplemented with saturated free fatty acid (FA) supplements (SFAA) compared with nonfat supplemented control diets (CON) on nutrient digestibility and production responses of lactating dairy cows and to determine whether experimental design affects responses to SFFA. We divided SFFA into C16:0-enriched supplements (PALM, FA supplements with ≥80% C16:0) and C16:0+C18:0-enriched supplements (MIX, FA supplements with ≥80% C16:0+C18:0). The database was formed from 32 peer-reviewed publications with SFFA supplemented at ≤3% diet dry matter (DM). We completed 3 different meta-analyses to meet our objectives. We analyzed the interaction between experimental design (continuous vs. change-over) and treatments (CON vs. SFFA; Meta.1). Regardless of experimental design, we evaluated the effect of treatment (CON vs. PALM vs. MIX; Meta.2) and the effect of 1-percentage-unit increase of MIX and PALM in diet DM (Meta.3). In Meta.1, there was no interaction between treatments and experimental design for any variable. In Meta.2, compared with CON, MIX had no effect on NDF digestibility, milk protein yield and energy corrected milk (ECM), increased the yields of milk (1.20 kg/d) and milk fat (0.04 kg/d), and decreased FA digestibility (5.20 percentage units). Compared with CON, PALM increased NDF digestibility (4.50 percentage units), the yields of milk (1.60 kg/d), milk fat (0.10 kg/d), milk protein (0.04 kg/d), and ECM (2.00 kg/d), and had no effect on FA digestibility. Compared with MIX, PALM tended to increase FA digestibility (3.20 percentage units), increased NDF digestibility (3.50 percentage units), milk fat yield (0.06 kg/d), and ECM (1.20 kg/d). In Meta.3, for each 1-percentage-unit increase of supplemental FA in diet DM, MIX had no effect on NDF digestibility, decreased FA digestibility, increased the yields of milk and milk fat, had no effect on milk protein yield, ECM and milk fat content, and decreased milk protein content. For each 1-percentage-unit increase of supplemental FA in diet DM, PALM increased NDF digestibility, had no effect on FA digestibility, increased the yields of milk, milk fat, ECM and milk fat content, tended to increase milk protein yield, and had no effect on milk protein content. Our results indicate no reason for the restrictive use of change-over designs in saturated FA supplementation studies and meta-analyses. Lactating dairy cows responded better to a FA supplement enriched in C16:0 compared with one containing C16:0 and C18:0.

Effect of Different Combinations of Dietary Vitamin A, Protein Levels, and Monensin on Inflammatory Markers and Metabolites, Retinol-Binding Protein, and Retinoid Status in Periparturient Dairy Cows

The objective of this study was to determine the effect of feeding different combinations of dietary vitamin A supplementation (0 or 110 IU/kg body weight), protein (10.3% or 12.2%), and an ionophore (monensin at 0 or 400 mg/day) on retinoid metabolism and immune function of dairy cows. Eighty multiparous Holstein dairy cows were studied from d -35 to +21 relative to expected parturition in a complete randomized block design with a 2 × 2 × 2 factorial arrangement of treatments. The significance of treatments was declared at p ≤ 0.05. Dairy cows receiving high crude protein (CP) diets with monensin had a greater retinol-binding protein serum concentration than cows receiving high CP diets without monensin (p = 0.04). Animals supplemented with vitamin A showed lower SCC (p = 0.04) and a higher thiobarbituric acid reactive substances concentration (p = 0.06) than cows non-supplemented. Moreover, cows receiving low crude protein diets had a greater haptoglobin concentration (p = 0.01). In addition, cows fed a high crude protein diet had a greater TNF-α expression in peripheral blood mononuclear cells (p = 0.04). Animals fed diets without monensin had a greater serum haptoglobin on day 3 postpartum than those fed monensin (p = 0.01). Moreover, dietary vitamin A increased serum 13-cis retinoic acid postpartum. We conclude that vitamin A, crude protein levels, and monensin fed during the close-up period affect milk somatic cell count, some vitamin statuses, and inflammatory markers during early lactation.

The Use of Monensin for Ketosis Prevention in Dairy Cows during the Transition Period: A Systematic Review

Since the approval by the European Medicines Agency in 2013 of a monensin controlled-release capsule (CRC) for the prevention of ketosis in dairy cows, there has been widespread use across Europe. In recent decades, several papers have investigated the effects of monensin used as a CRC or as a feed additive to improve cattle energy metabolism and improve feed efficiency. Since the CRC is the only form of monensin permitted in Europe in dairy cows, the objective of this review was to report and summarize observations from the literature on the effects of this treatment in transition cows. The peer-reviewed literature published from 1997 was scanned, and papers written in English were evaluated for eligibility. Only papers evaluating the use of monensin in dairy cows for the prevention of ketosis during the transition period were reviewed. In total, 42 papers met the required criteria and were included in this review. The major findings focused on cow metabolism and health, rumen fermentation and milk production and quality. Overall, the review of the existing literature confirmed that monensin delivered as a CRC during the transition period has effects of different magnitude compared to other forms, doses or durations of administration. Studies agree on the antiketotic effects of this treatment, showing evidence of an increased propionate production in the rumen, reduced blood β-hydroxybutyrate, and improved liver function in treated cows, mainly resulting in reduced incidence of peripartum disease. On the contrary, the effects of CRC on ammonia production and rumen microflora are less robust than those reported for other forms. Of importance for the European market is the well-documented absence of any negative impact on milk and cheese production and composition using the CRC treatment.

Effects of calcium salts of palm fatty acids on nutrient digestibility and production responses of lactating dairy cows: A meta-analysis and meta-regression

Our primary objective was to perform a meta-analysis and meta-regression to evaluate the effects of diets supplemented with calcium salts of palm fatty acids (CSPF) compared with nonfat supplemented control diets (CON) on nutrient digestibility and production responses of lactating dairy cows. Our secondary objective was to perform a meta-analysis to evaluate whether experimental design affects production responses to supplemental CSPF. The data set was formed from 33 peer-reviewed publications with CSPF supplemented at ≤3% diet dry matter. We analyzed the interaction between experimental design (continuous vs. change-over) and treatments (CON vs. CSPF) to evaluate whether experimental design affects responses to CSPF (Meta.1). Regardless of experimental design, we evaluated the effects of CSPF compared with CON on nutrient digestibility and production responses of lactating dairy cows by meta-analysis (Meta.2) and meta-regression (Meta.3) approaches. In Meta.1, there was no interaction between treatments and experimental design for any variable. In Meta.2, compared with CON, CSPF reduced dry matter intake [DMI, 0.56 ± 0.21 kg/d (±SE)] and milk protein content (0.05 ± 0.02 g/100 g), increased neutral detergent fiber (NDF) digestibility (1.60 ± 0.57 percentage units), the yields of milk (1.53 ± 0.56 kg/d), milk fat (0.04 ± 0.02 kg/d), and 3.5% fat corrected milk (FCM, 1.28 ± 0.60 kg/d), and improved feed efficiency [energy corrected milk (ECM)/DMI, 0.08 kg/kg ± 0.03]. There was no effect of treatment for milk protein yield, milk fat content, body weight, body weight change, or body condition score. Compared with CON, CSPF reduced the yield of de novo milk fatty acids (FA) and increased the yields of mixed and preformed milk FA. In Meta.3, we observed that each 1-percentage-unit increase of CSPF in diet dry matter reduced DMI, increased NDF digestibility, tended to increase FA digestibility, increased the yields of milk, milk fat, and 3.5% FCM, reduced the content of milk protein, reduced the yield of de novo milk FA, and increased the yields of mixed and preformed milk FA. In conclusion, our results indicate no reason for the restrictive use of change-over designs in CSPF supplementation studies or meta-analysis. Feeding CSPF increased NDF digestibility, tended to increase FA digestibility, and increased the yields of milk, milk fat, and 3.5% FCM. Additionally, CSPF increased milk fat yield by increasing the yields of mixed and preformed milk FA.

Effect of monensin on milk fatty acid profile in dairy cows and on the use of fatty acids for early diagnosis of elevated blood plasma concentrations of nonesterified fatty acids and hyperketonemia

This work examined the effects of precalving administration of continuous-release monensin capsule on postcalving milk fatty acid (FA) profile and on the accuracy of FA as a biomarker in the early identification of cows with elevated blood plasma nonesterified fatty acids (NEFA) and β-hydroxybutyrate (BHB) concentrations. Approximately 3 wk before expected calving, 203 multiparous Estonian Holstein cows were randomly divided into control (CO; n = 116) and experimental (MO; n = 87) groups, and a continuous-release capsule of monensin was administered to the MO cows. Blood samples were taken daily in the first 4 d postpartum, then on the sixth or seventh day in milk, twice in the second week, and thenceforth once per week until the end of the sixth week. Milk samples were taken once from 4 to 7 d in milk, twice in the second week, and thenceforth once per week. Blood samples were analyzed for NEFA and BHB, and milk was analyzed for FA concentrations. Cows with postpartum BHB concentrations ≥1.2 mmol/L at least once during the 6 wk were classified as hyperketonemic (HYK), and cows with NEFA concentrations ≥1.0 mmol/L as having elevated concentration of NEFA (NEFA_H). The ability of FA to predict NEFA_H and HYK cows was studied with logistic regression and receiver operating characteristic curve analysis and the identification accuracy was estimated by area under the receiver operating characteristic curve. For these analyses, we used FA measured on the ninth day after calving. Monensin administration affected FA mobilization and metabolism of the animals as blood NEFA were lower in the MO group on wk 1 and wk 3, and BHB values were considerably lower from wk 1 to wk 4 compared with the CO group. The FA dynamics were generally similar for MO and CO groups. Monensin administration resulted in higher concentrations of C15:0, C16:0, iso C17:0, anteiso C15:0, anteiso C17:0, total trans monounsaturated FA, and C18:2 cis-9,trans-11, and lower proportions of C18:0, C18:1 cis-9, and most of the iso FA. The identification accuracy of NEFA_H and HYK cows was higher in the CO compared with the MO group and for the identification of HYK compared with NEFA_H cows (0.75-0.77 vs. 0.78-0.80 in the CO group, and 0.61-0.66 vs. 0.68-0.75 in the MO group for NEFA_H vs. HYK, respectively). For all FA, the threshold values to identify NEFA_H and HYK cows were different in the CO and MO groups. Results suggest that specific threshold values for the identification of NEFA_H and HYK cows could be applicable only within similar feeding conditions and rumen environment.

Ketone bodies - causes and effects of their increased presence in cows' body fluids: A review

Ketosis is the most common metabolic disease in high-performance dairy cows during the first 6-8 weeks of lactation. Its main symptoms include an excessive amount of so-called ketone bodies in a cow's body fluids. Ketone bodies consist of β-hydroxybutyric acid (βHBA), acetoacetic acid, and acetone. βHBA is the main component with its share of the total volume of ketone bodies in the blood of about 70%. Clinical symptoms of ketosis in cows include loss of appetite, preference for forage to concentrated feed, and acetone odor in their mouth and urine. Those symptoms are accompanied by a production drop, an increase of concurrent illness (mastitis, metritis, and displaced abomasum), and poor reproductive performance. One of the ketosis characteristic effects is an increase in the level of fat in milk (>5%), while protein levels decrease (<2.9%). In the case of subclinical ketosis (SCK), the fat-protein ratio in milk is increased to above 1.4:1. The current consensus for SCK is to consider a cutoff point of βHBA to be at least 1.2 mmol/L in blood plasma. Ketosis prevention is based on keeping perinatal cows in good condition, that is, with around 3.5 points in the five-point body condition scoring, carefully balancing food doses during the first 2 months of lactation with the correct energy-protein ratio. Glucose precursor products should be administered orally, in particular to at-risk herds. Ketosis occurs in 7-14% on average of the total number of cows in a herd. In general, data on the prevalence of SCK vary considerably, depending on their source. Moreover, the problem is mostly observed in poorly-fed animals with high milk production potential. The objectives of this review are to reveal the current situation of ketosis prevalence, the possibility of diagnosis, consequences in dairy cows and to provide some recommendations for ketosis treatment and prevention.

Effects of supplementation with narasin, salinomycin, or flavomycin on performance and ruminal fermentation characteristics of Bos indicus Nellore cattle fed with forage-based diets

The aim of the present study was to evaluate the inclusion of narasin, salinomycin, or flavomycin for 140 d on ruminal fermentation parameters, apparent nutrient digestibility, and performance of Nellore cattle offered a forage-based diet. In experiment 1, 32 rumen-cannulated Bos indicus Nellore steers [initial body weight (BW) = 220 ± 12.6 kg] were assigned to individual pens in a randomized complete block design according to their initial shrunk BW. Within block, animals were randomly assigned to 1 of 4 treatments: (1) forage-based diet without feed additives (CON; n = 8), (2) CON diet plus 13 ppm of narasin (NAR; n = 8), (3) CON diet plus 20 ppm of salinomycin (SAL; n = 8), or (4) CON diet plus 3 ppm of flavomycin (FLA; n = 8). The experimental period lasted 140 d and was divided into 5 periods of 28 d each. The inclusion of feed additives did not impact (P ≥ 0.17) dry matter intake (DMI), nutrient intake, and apparent total tract digestibility of nutrients. Nonetheless, steers fed NAR had lower (P < 0.01) molar proportion of acetate compared with CON, SAL, and FLA steers, whereas ruminal acetate tended to be greater (P < 0.09) for SAL vs. CON and FLA, but did not differ (P = 0.68) between CON vs. FLA steers. Ruminal propionate was the highest (P < 0.01) for steers fed NAR and did not differ (P > 0.20) between CON, SAL, and FLA. Consequently, NAR steers had the lowest (P < 0.01) Ac:Pr ratio, whereas Ac:Pr did not differ (P > 0.18) among CON, SAL, and FLA. Total volatile fatty acids were greater (P < 0.04) for NAR and CON vs. SAL and FLA, but did not differ (P > 0.67) among NAR vs. CON and SAL vs. FLA. In experiment 2, 164 Nellore bulls (initial shrunk BW = 299 ± 2.5 kg) were assigned to feedlot pens for 140 d in a randomized complete block design. Within block (n = 10), animals were randomly assigned to the same treatments used in experiment 1. Average daily gain was greater (P < 0.01) in NAR vs. CON, SAL, and FLA bulls, and did not differ (P > 0.12) between CON, SAL, and FLA bulls. Bulls fed NAR had greater (P < 0.02) DMI (as kg/d or % BW) and final shrunk BW compared with CON, SAL, and FLA bulls, whereas DMI and final shrunk BW did not differ (P > 0.26) between CON, SAL, and FLA bulls. Feed efficiency, however, was not impacted (P = 0.51) by any feed additives used herein. Collectively, narasin was the only feed additive that benefited performance and ruminal fermentation of Nellore animals fed a forage-based diet.

Comparison between two preventive treatments for hyperketonaemia carried out pre-partum: effects on non-esterified fatty acids, β-hydroxybutyrate and some biochemical parameters during peripartum and early lactation

The objective of this study was to compare the effect of two different preventive protocols, on serum β-hydroxybutyrate (BHB) concentration and liver health indices pre-partum and during early-lactation in high-yielding Holstein dairy cows. One hundred cows were randomly divided into three groups: control group (CTRL, n = 20, without preventive treatment), second group (SUPP, n = 40 animals treated with a compound based on acetyl-methionine, inositol, cyanocobalamin, l-alanine, l-arginine, l-threonine, l-glutamic acid supplementation and α-lipoic acid) and third group (MON, n = 40 animals treated with monensin). Blood samples were collected from all cows at on 3 occasions pre-partum and 3 occasions post-partum. Body condition (BCS) score was evaluated and glucose, non-esterified fatty acids (NEFA), BHB, triglycerides, total cholesterol, alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltransferase (GGT), total bilirubin, total proteins, globulins, albumin and urea concentrations were assessed. Two-way repeated measures analysis of variance was applied. Statistically significant differences among the three experimental groups were found in the values of all studied parameters (P < 0.05). Our results confirm the established beneficial effect of MON treatment in decreasing BHB levels and increasing glucose availability after calving. Serum biochemical analysis revealed the expected post-partum alterations attributable to adaptations that influenced the metabolism and liver function in CTRL, whereas these alterations were reduced or absent in SUPP and MON. Results from the present study suggest that both preventive protocols, but in particular SUPP, could positively affect selected indicators of energy metabolism reducing the risk of hyperketonaemia and increase of liver function in Holstein dairy cows, both pre- and post-partum.

Effects of prepartum diets varying in dietary energy density and monensin on early-lactation performance in dairy cows

Our objectives were to evaluate the effects of prepartum monensin supplementation and dry-period nutritional strategy on the postpartum productive performance of cows fed monensin during lactation. A total of 102 Holstein cows were enrolled in the experiment (32 primiparous and 70 multiparous). The study was a completely randomized design, with randomization restricted to balance for parity, body condition score, and expected calving date. A 2 × 2 factorial arrangement of prepartum treatments was used; the variables of interest were prepartum feeding strategy [controlled-energy diet throughout the dry period (CE) vs. controlled-energy diet from dry-off to 22 d before expected parturition, followed by a moderate-energy close-up diet from d 21 before expected parturition through parturition (CU)] and prepartum monensin supplementation [0 g/t (control, CON) or 24.2 g/t (MON); Rumensin; Elanco Animal Health, Greenfield, IN]. Lactation diets before and after the dry period contained monensin at 15.4 g/t. During the close-up period, cows fed CU had greater DM and NE_L intakes than cows fed CE. Calf BW at birth tended to be greater for cows fed CU than for those fed CE but was not affected by MON supplementation. Diet did not affect calving difficulty score, but cows supplemented with MON had an increased calving difficulty score. We found a tendency for a MON × parity interaction for colostral IgG concentration, such that multiparous MON cows tended to have lower IgG concentration than CON cows, but colostral IgG concentration for primiparous MON and CON cows did not differ. Postpartum milk yield did not differ between diets but tended to be greater for cows supplemented with MON. Milk fat and lactose content were greater for cows fed CU than for those fed CE, and lactose content and yield were increased for cows supplemented with MON. Solids-corrected and fat-corrected milk yields were increased by MON supplementation, but were not affected by diet. Overall means for postpartum DMI did not differ by diet or MON supplementation. The CU diet decreased the concentration of nonesterified fatty acids during the close-up period but increased it postpartum. Neither diet nor monensin affected β-hydroxybutyrate or liver composition. Overall, postpartum productive performance differed little between prepartum dietary strategies, but cows fed MON had greater energy-corrected milk production. In herds fed monensin during lactation, monensin should also be fed during the dry period.

Transient reductions in milk fat synthesis and their association with the ruminal and metabolic profile in dairy cows fed high-starch, low-fat diets

Sub-acute ruminal acidosis (SARA) is sometimes observed along with reduced milk fat synthesis. Inconsistent responses may be explained by dietary fat levels. Twelve ruminally cannulated cows were used in a Latin square design investigating the timing of metabolic and milk fat changes during Induction and Recovery from SARA by altering starch levels in low-fat diets. Treatments were (1) SARA Induction, (2) Recovery and (3) Control. Sub-acute ruminal acidosis was induced by feeding a diet containing 29.4% starch, 24.0% NDF and 2.8% fatty acids (FAs), whereas the Recovery and Control diets contained 19.9% starch, 31.0% NDF and 2.6% FA. Relative to Control, DM intake (DMI) and milk yield were higher in SARA from days 14 to 21 and from days 10 to 21, respectively (P < 0.05). Milk fat content was reduced from days 3 to 14 in SARA (P < 0.05) compared with Control, while greater protein and lactose contents were observed from days 14 to 21 and 3 to 21, respectively (P < 0.05). Milk fat yield was reduced by SARA on day 3 (P < 0.05), whereas both protein and lactose yields were higher on days 14 and 21 (P < 0.05). The ruminal acetate-to-propionate ratio was lower, and the concentrations of propionate and lactate were higher in the SARA treatment compared with Control on day 21 (P < 0.05). Plasma insulin increased during SARA, whereas plasma non-esterified fatty acids and milk β-hydroxybutyrate decreased (P < 0.05). Similarly to fat yield, the yield of milk preformed FA (>16C) was lower on day 3 (P < 0.05) and tended to be lower on day 7 in SARA cows (P < 0.10), whereas yield of de novo FA (<16C) was higher on day 21 (P < 0.01) in the SARA group relative to Control. The t10- to t11-18:1 ratio increased during the SARA Induction period (P < 0.05), but the concentration of t10-18:1 remained below 0.5% of milk fat, and t10,c12 conjugated linoleic acid remained below detection levels. Odd-chain FA increased, whereas branched-chain FA was reduced during SARA Induction from days 3 to 21 (P < 0.05). Sub-acute ruminal acidosis reduced milk fat synthesis transiently. Such reduction was not associated with ruminal biohydrogenation intermediates but rather with a transient reduction in supply of preformed FA. Subsequent rescue of milk fat synthesis may be associated with higher availability of substrates due to increased DMI during SARA.

Effects of narasin supplementation on dry matter intake and rumen fermentation characteristics of Bos indicus steers fed a high-forage diet

This study evaluated the effects of narasin on intake and rumen fermentation characteristics of Bos indicus steers offered a high-forage diet for 140 d. On day 0 of the study, 30 rumen-fistulated Nellore steers [initial body weight (BW) = 281 ± 21 kg] were assigned to 30 individual pens in a randomized complete block design according to their initial BW. Animals were randomly assigned to 1 of the 3 treatments: 1) forage-based diet without narasin (CONT; n = 10), 2) CONT diet plus 13 ppm of narasin (13NAR; n = 10), and 3) CONT diet plus 20 ppm of narasin (20NAR; n = 10). The forage used was Tifton-85 (Cynodon dactylon spp.), whereas the carrier for narasin was a 50:50 mixture of soybean hull:corn. The experimental period was divided into 5 periods of 28 d each. Throughout the experimental period, total dry matter intake (DMI) was recorded daily, whereas mineral salt intake was recorded weekly. Blood and ruminal fluid samples were collected on day 0 (prior to treatment feeding), 28, 56, 84, 112, and 140 of the study. Moreover, total tract apparent nutrient digestibility was performed for a 5-d period every 28 d. No treatment effects were observed on forage, mineral, concentrate, or total DMI (P ≥ 0.22). Nonetheless, 13NAR tended to have a greater mineral intake vs. 20NAR cohorts (P = 0.08) Narasin-supplemented animals had reduced rumen acetate, Ac:Pr ratio, as well as greater (P ≤ 0.02) rumen propionate concentrations vs. CONT cohorts. Moreover, 13NAR increased rumen propionate and decreased butyrate, Ac:Pr vs. 20NAR cohorts (P ≤ 0.01). Throughout the experimental period, narasin-supplemented animals had reduced ammonia concentrations vs. CONT cohorts (P < 0.01), whereas no differences were observed between 13NAR and 20NAR (P = 0.80). No treatment or dose effects were observed (P ≥ 0.23) on DM, organic matter (OM), protein, neutral detergent fiber (NDF), acid detergent fiber (ADF), and mineral digestibility. Animals fed 13NAR had a reduced mean plasma urea concentration vs. CONT cohorts (P = 0.03), whereas no further differences were observed (P ≥ 0.12). In summary, narasin supplementation to beef steers offered a high-forage diet did not impact forage, mineral, and total DMI, as well as nutrient digestibility, whereas rumen fermentation characteristics, rumen ammonia, and plasma urea concentrations were positively impacted and lasted throughout the experimental period. Additionally, 13 ppm of narasin resulted in a reduced Ac:Pr ratio and rumen ammonia when compared to animals supplemented with 20 ppm.

Effects of fixed-time artificial insemination using triptorelin on the reproductive performance of pigs: a meta-analysis

Triptorelin (TRI), a gonadotropin-releasing hormone agonist allowing ovulation synchronization in pigs, is indispensable for fixed-time artificial insemination (FTAI) protocols. However, the effect of FTAI using TRI (FTAI-TRI) on the reproductive performance is controversial. We performed a meta-analysis to determine whether FTAI-TRI affects reproductive performance of pigs, including pregnancy rate (PR), number of pigs born alive per litter (NBA), farrowing rate (FR) and total number of pigs born per litter (TNB). A total of 37 trials from 15 studies were extracted and analysed in Stata. A weighted mean difference (WMD) with 95% confidence interval (CI) was calculated for NBA and TNB, and risk ratio (RR) with 95% CI was calculated for PR and FR. Pregnancy rate, TNB and NBA data were applied to a fixed-effect protocol, and FR data were applied to a random-effect protocol. We found that for weaned sows, the FTAI-TRI group had comparable reproductive performance to the artificial insemination (AI) following oestrus detection (EDAI) group. Fixed-time AI has many advantages, including the elimination of the need to heat-check twice daily, so that FTAI-TRI is a good substitute for EDAI. Subgroup analysis indicated that the optimal timing of triptorelin treatment was 96 h after weaning, which gave significant positive effects on PR (RR = 1.08, P = 0.000) and non-significant positive effects on TNB (WMD = 0.12, P = 0.452). Triptorelin at a dose of 100 μg showed better effects than 200 μg, with significant positive effects on PR (RR = 1.09, P = 0.005) and FR (RR = 1.06, P = 0.036). So a single dose of 100 μg was recommended. The optimal protocol was insemination at 24 h and again at 48 h after triptorelin administration if they remained in standing oestrus, and this provided a significantly higher NBA (WMD = 0.59, P = 0.013) that increased by 0.59. For gilts, the FTAI-TRI group showed decreased (not significant) PR (RR = 0.96, P = 0.127) and significantly decreased FR (RR = 0.93, P = 0.013), TNB (WMD = -0.85, P = 0.006) and NBA (WMD = -0.98, P = 0.000), which were inferior to those in the EDAI group. In conclusion, the effects of FTAI-TRI on the reproductive performance of pigs were parity-, treatment timing-, insemination timing-, and dosage-dependent. Fixed-time AI using triptorelin could effectively replace the EDAI protocol for sows, but not for gilts.

Nutritional strategies for alleviating the detrimental effects of heat stress in dairy cows: a review

Heat stress responses negatively impact production performance, milk quality, body temperature, and other parameters in dairy cows. As global warming continues unabated, heat stress in dairy cows is likely to become more widespread in the future. To address this challenge, researchers have evaluated a number of potentially available nutritional strategies, including dietary fat, dietary fiber, dietary microbial additives, minerals, vitamins, metal ion buffer, plant extracts, and other anti-stress additives. In this paper, we discuss the evidence for the efficacy of these nutritional strategies aimed at alleviating the detrimental effects of heat stress in dairy cows. It was comprised of the treatment (dosage and usage), animal information (lactation stage and number of dairy cows), THI value (level of heat stress), duration of exposure, the changes of feed intake and milk yield (production performance), the changes of milk protein and milk fat (milk quality), the changes of rectal temperature and respiration rate (body temperature), other indices, and reference resources. The results of these studies are presented with statistical justification in the tables. In total, the 49 kinds of dietary interventions derived from these eight types of nutritional strategies may provide an appropriate means of mitigating heat stress on a particular dairy farm based on the explanation of the results.

Effects of chitosan and whole raw soybeans on ruminal fermentation and bacterial populations, and milk fatty acid profile in dairy cows

The objective of this study was to evaluate whether providing chitosan (CHI) to cows fed diets supplemented with whole raw soybeans (WRS) would affect the nutrient intake and digestibility, ruminal fermentation and bacterial populations, microbial protein synthesis, N utilization, blood metabolites, and milk yield and composition of dairy cows. Twenty-four multiparous Holstein cows (141 ± 37.1 d in milk, 38.8 ± 6.42 kg/d of milk yield; mean ± SD) were enrolled to a 4 × 4 Latin square design experiment with 23-d periods. Cows were blocked within Latin squares according to milk yield, days in milk, body weight, and rumen cannula (n = 8). A 2 × 2 factorial treatment arrangement was randomly assigned to cows within blocks. Treatments were composed of diets with 2 inclusion rates of WRS (0 or 14% diet dry matter) and 2 doses of CHI (0 or 4 g/kg of dry matter, Polymar Ciência e Nutrição, Fortaleza, Brazil). In general, CHI+WRS negatively affected nutrient intake and digestibility of cows, decreasing milk yield and solids production. The CHI increased ruminal pH and decreased acetate to propionate ratio, and WRS reduced NH3-N concentration and acetate to propionate in the rumen. The CHI reduced the relative bacterial population of Butyrivibrio group, whereas WRS decreased the relative bacterial population of Butyrivibrio group, and Fibrobacter succinogenes, and increased the relative bacterial population of Streptococcus bovis. No interaction effects between CHI and WRS were observed on ruminal fermentation and bacterial populations. The CHI+WRS decreased N intake, microbial N synthesis, and N secreted in milk of cows. The WRS increased N excreted in feces and consequently decreased the N excreted in urine. The CHI had no effects on blood metabolites, but WRS decreased blood concentrations of glucose and increased blood cholesterol concentration. The CHI and WRS improved efficiency of milk yield of cows in terms of fat-corrected milk, energy-corrected milk, and net energy of lactation. The CHI increased milk concentration [g/100 g of fatty acids (FA)] of 18:1 trans-11, 18:2 cis-9,cis-12, 18:3 cis-9,cis-12,cis-15, 18:1 cis-9,trans-11, total monounsaturated FA, and total polyunsaturated FA. The WRS increased total monounsaturated FA, polyunsaturated FA, and 18:0 to unsaturated FA ratio in milk of cows. Evidence indicates that supplementing diets with unsaturated fat sources along with CHI negatively affects nutrient intake and digestibility of cows, resulting in less milk production. Diet supplementation with CHI or WRS can improve feed efficiency and increases unsaturated FA concentration in milk of dairy cows.

EFFECTS OF DIETARY SODIUM MONENSIN ON THE METABOLIC AND HORMONAL PROFILES OF DAIRY GOATS DURING THE PERIPARTUM PERIOD

Abstract This study aimed to investigate the energetic and hormonal profiles of dairy goats fed diets supplemented with monensin during the peripartum period. Eleven pregnant Saanen goats were subdivided into two random groups, a control group (GC) and the monensin group (MG). The MG group received 40 mg sodium monensin per animal per day for 15 days before partum and throughout the subsequent experimental period. Clinical observations and sample collection were performed at 30, 15, and 7 days before birth; on the day of partum; and at 5, 15, and 30 days after birth. The following biochemical and hormonal profile variables analyzed were: cholesterol, triglycerides, glucose, fructosamine, non-esterified fatty acids (NEFAs) and β-hydroxybutyrate (BHB), cortisol, and insulin. The ruminal fluid pH, chloride content, and volatile fatty acids were also measured. Statistical analysis of the data was performed using repeated measures ANOVA (p < 0.05) and Pearson's correlation. At partum, the MG group had lower values of NEFAs and lower acetate/propionate ratio. MG had higher triglycerides during the entire experiment period. The administration of monensin generated benefits in terms of energy parameters, improving the metabolic status of the dairy goats during peripartum.

Short communication: Meta-analysis on therapy of bovine endometritis with prostaglandin F2α-An update

The objective of the study was to update a prior meta-analysis on the efficacy of the treatment of bovine endometritis with PGF_2α. Clinical endometritis in cattle is defined as the presence of a purulent or mucopurulent vaginal discharge after 20 or 26 d, respectively, postpartum. Although the prevalence and impact of this disease are well known, the questions of whether and how to treat endometritis are still controversially discussed. Hence, to ensure timeliness of scientific results, we updated an existing meta-analysis published in 2013 that showed no treatment effect of PGF_2α in cases of bovine endometritis. As in the prior meta-analysis, a comprehensive literature search was conducted. After applying specific inclusion and exclusion criteria, 3 trials remained that could be added to the 6 trials in the initial meta-analysis. Data for each trial were analyzed using the meta-analysis software Review Manager (version 5.3; The Nordic Cochrane Centre, Copenhagen, Denmark). Estimated effect sizes of PGF_2α were calculated on calving to first service interval (CFSI) and calving to conception interval (CCI). As revealed by the initial meta-analysis, PGF_2α treatment still had no effect on both reproductive parameters. Heterogeneity remained substantial for CFSI and CCI and even increased for CCI compared with the initial meta-analysis. Subgroup analysis, however, did not reveal a source of heterogeneity. In updating the meta-analysis, publication bias for trials reporting CCI became even more pronounced, suggesting that studies with higher standard error (i.e., usually smaller studies) that reported a prolonging effect on CCI after a PGF_2α treatment were less likely to be published. Finally, although the number of trials published on the chosen topic and their comparability are still limited, this update of our meta-analysis now provides results that are based on approximately twice the number of included cows. The overall outcome, however, has not substantially changed and a positive effect of a PGF_2α treatment in case of clinical endometritis could not be shown. Therefore, we do not recommend a treatment of bovine endometritis with PGF_2α as a means to improve reproductive performance.

Effects of a combination of plant bioactive lipid compounds and biotin compared with monensin on body condition, energy metabolism and milk performance in transition dairy cows

The aim of this study was to test whether a combination of plant bioactive lipid compounds (also termed ‘essential oils’) and biotin (PBLC+B) could decrease the mobilization of body reserves and ketosis incidence in postpartum dairy cows. We compared non-supplemented control (CON) cows with cows receiving monensin (MON) as a controlled-release capsule at d -21, and with cows receiving PBLC+B from day (d) -21 before calving until calving (Phase 1) and further until d 37 after calving (Phase 2), followed by PBLC+B discontinuation from d 38 to d 58 (Phase 3). The PBLC+B cows had higher body weight and higher back fat thickness than CON cows and lesser body weight change than MON and CON cows in Phase 3. Body condition score was not different among groups. Milk protein concentration tended to be higher on the first herd test day in PBLC+B vs. CON cows. Milk fat concentration tended to be highest in PBLC+B cows throughout Phases 2 and 3, with significantly higher values in PBLC+B vs. MON cows on the second herd test day. Yields of energy-corrected milk were higher in PBLC+B vs. CON and MON cows in Phase 2 and higher in PBLC+B and MON cows vs. CON cows in Phase 3. The incidence of subclinical ketosis was 83%, 61% and 50% in CON, PBLC+B and MON cows, respectively, with lower mean β-hydroxybutyrate values in MON than in PBLC+B cows in Phase 1 prepartum. The serum triglyceride concentration was higher in PBLC+B vs. CON cows on d 37. No differences were observed in serum glucose, urea, non-esterified fatty acids, cholesterol and bilirubin concentrations. Aspartate transaminase and γ-glutamyltranspeptidase but not glutamate dehydrogenase activities tended to be highest in MON and lowest in PBLC+B in Phase 2. We conclude that PBLC+B prevent body weight loss after parturition and are associated with similar ketosis incidence and partly higher yields of energy-corrected milk compared to MON supplementation of dairy cows.

Effect of the ionophore monensin and tannin extracts supplemented to grass silage on populations of ruminal cellulolytics and methanogens in vitro

This study examined whether the methane-decreasing effect of monensin (∼21%) and different hydrolysable tannins (24%-65%) during in vitro fermentation of grass silage was accompanied by changes in abundances of cellulolytics and methanogens. Samples of liquid (LAM) and solid (SAM) associated microbes were obtained from two rumen simulation technique experiments in which grass silage was either tested in combination with monensin (0, 2 or 4 mg d^-1) or with different tannin extracts from chestnut, valonea, sumac and grape seed (0 or 1.5 g d^-1). Total prokaryotes were quantified by 4',6-diamidino-2-phenylindol (DAPI) staining of paraformaldehyde-ethanol-fixed cells and relative abundances of ruminal cellulolytic and methanogenic species were assessed by real time quantitative PCR. Results revealed no change in absolute numbers of prokaryotic cells with monensin treatment, neither in LAM nor in SAM. By contrast, supplementation of chestnut and grape seed tannins decreased total prokaryotic counts compared to control. However, relative abundances of total methanogens did not differ between tannin treatments. Thus, the decreased methane production by 65% and 24% observed for chestnut and grape seed tannins, respectively, may have been caused by a lower total number of methanogens, but methane production seemed to be also dependent on changes in the microbial community composition. While the relative abundance of F. succinogenes decreased with monensin addition, chestnut and valonea tannins inhibited R. albus. Moreover, a decline in relative abundances of Methanobrevibacter sp., especially M. ruminantium, and Methanosphaera stadtmanae was shown with supplementation of monensin or chestnut tannins. Proportions of Methanomicrobium mobile were decreased by monensin in LAM while chestnut and valonea had an increasing effect on this methanogenic species. Our results demonstrate a different impact of monensin and tannins on ruminal cellulolytics and gave indication that methane decrease by monensin and chestnut tannins was associated with decreased abundances of M. ruminantium and M. stadtmanae.