The relationships of dairy ruminal odd- and branched- chain fatty acids to the duodenal bacterial nitrogen flow and volatile fatty acids

Supplementation of isoacids to lactating dairy cows fed low- or high-forage diets: Effects on performance, digestibility, and milk fatty acid profile

Our objective was to determine the effects of isoacids (ISO) on the lactation performance, digestibility, and milk fatty acids (FA) profile of Holstein cows fed 2 forage NDF levels (FL). The study lasted 10 wk (including 2 wk for covariate) using a randomized complete block design. Sixty-four mid-lactating Holstein cows (662 ± 71 kg BW, 119 ± 51 DIM, 2 ± 0.9 parity [±SD]) were blocked by parity, DIM, and prior milk yield (MY) for multiparous cows or genetic merit for primiparous cows, and randomly assigned to 1 of the 4 diets (n = 16). Diets were arranged as a 2 × 2 factorial, with 2 FL containing 21% forage (HF) and 17% forage NDF (LF) without (WIA) or with ISO supplementation (IA; 7.85 mmol/kg of DM and 3.44 mmol/kg of DM for isobutyrate and 2-methylbutyrate, respectively). Diets were balanced for similar NEL (1.58 Mcal/kg of DM), CP (16.0%), and total NDF (27.2%). Feed intake and MY were recorded daily. Nutrient digestibility for each cow was determined using indigestible NDF as a marker, and fecal samples were collected at 8-time points (4-h intervals between samples). Individual cow milk samples composited over a 10-wk period were analyzed using GC for FA profile. The statistical model included FL, ISO, and FL × ISO as fixed effects and block as a random effect (lme4 in R). The ISO did not affect DMI, and LF cows had greater DMI than HF cows (27.8 vs. 26.0 kg/d). However, ISO increased MY (34.7 vs. 37.2 kg/d) and ECM (41.9 vs. 39.0 kg/d) by 7% in cows fed the HF but not in those fed the LF diet, suggesting a FL × ISO interaction. Interestingly, ISO increased ADG (0.4 kg/d) but decreased MUN by 9% only in LF diet as indicated by the FL × ISO interaction. Additionally, ISO increased DM, OM, NDF, and CP digestibility by 10% to 24% in HF, but not in LF (FL × ISO). As expected, ISO increased milk odd-chain FA profiles in the IA groups irrespective of FL; for example, the IA had greater C15:0 (1.87 vs. 1.54 g/100g FA) and a tendency to be greater C17:0 levels (0.86 vs. 0.76 g/100g FA) compared with WIA groups. Overall, ISO improved MY and nutrient digestibility in cows fed the HF diets, whereas it increased ADG and decreased MUN in cows fed the LF diet. Additionally, ISO increased milk odd-chain FA (C15:0 and C17:0) regardless of FL.

Adding of Allium mongolicum regel extracts to lamb feedlot diets influences 4-alkyl-branched fatty acids deposition and the meat quality during storage

The present study aimed to investigate the effect of dietary supplementation with Allium mongolicum Regel extracts on the 4-alkyl-branched fatty acid deposition and meat quality during storage. Small-tailed Han sheep were divided into four groups (n = 15) and fed for 75 days with a basal diet (CK), CK supplemented with A. mongolicum Regel powder (AMR), A. mongolicum Regel water-soluble extract (AWE), or A. mongolicum Regel ethanol-soluble extract (AFE). The results revealed that both AMR and AWE diets decreased the 4-alkyl-branched fatty acids content in longissimus thoracis. Diet × storage time interactions were observed for acid value (AV), peroxidase (POx), glutathione peroxidase (GSH-Px), and total volatile base nitrogen (TVB-N). Patterns of change for AV, POx, and GSH-Px over time leading to the interactions were not readily apparent and changes were more governed by main effects. Dietary supplementation with AMR and AWE increased the total antioxidant capacity, total superoxide dismutase, and inhibited total bacteria counts compared to those in the CK lambs. The AWE diet also decreased the yellowness and hue angle. Overall, A. mongolicum Regel and its extracts could be used as a source of natural bioactive compounds in the lambs' diet to extend the storage time of their meat.

Synchronization of rumen degradable protein with non-fiber carbohydrate on microbial protein synthesis and dairy ration digestibility

Background and Aim: Dairy ration formulations should consider the synchronization of the rumen degradable protein (RDP) to rumen undegradable protein (RUP) ratio (RDPR) with non-fiber carbohydrate (NFC) to achieve optimum microbial protein synthesis (MPS), reduce feed costs, and reduce N excretion to the environment. This study aimed to investigate the effect of RDPR and NFC synchronization on in vitro digestibility, fermentability, and MPS. Materials and Methods: The experiment used a 3×3 factorial randomized block design with four replications. The first factor was RDPR (RDPR1=50:50; RDPR2=55:45; RDPR3=60:40) and the second factor was NFC levels (NFC1=30%, NFC2=35%, NFC3=40%). The experimental diets were evaluated using a two-stage in vitro method. The examined parameters included rumen pH, NH3 concentration, total volatile fatty acid (VFA) concentration, the molar proportion of VFAs, rumen microbes (protozoa and total bacteria population), and MPS. Data were analyzed using ANOVA, followed by the Duncan test. Results: The results show that neither RDPR nor NFC affected rumen pH, NH3, total VFA, and the rumen microbe population. The interaction between RDPR and NFC affected the molar proportion of acetate, iso-butyrate, and n-valerate. The combination of RDPR1 and NFC1 produced a lower molar proportion of acetate (49.73%) than the other treatment combinations (>54%). The acetate to propionate ratio was influenced by the NFC levels, in which NFC2 and NFC3 produced the highest ratio (p<0.05). MPS was affected by RDPR and NFC, but not by their interaction. Treatments NFC2 and RDPR3 produced the highest MPS. NFC affected the dry matter and organic matter digestibility (DMD and OMD), with treatment NFC3 resulting in the highest DMD and OMD. Conclusion: The combination of a 60:40 RDPR with 35% NFC resulted in the best synchronization of protein and energy available for MPS and digestion activity in the rumen.

Ruminal cellulolytic bacteria abundance leads to the variation in fatty acids in the rumen digesta and meat of fattening lambs

Ruminal cellulolytic bacteria could be a diagnostic tool for determining the subacute rumen acidosis (SARA) risk in individual ruminants; however, a limited number of studies have investigated the effects of the abundance of ruminal cellulolytic bacteria on the fatty acid (FA) composition of the rumen digesta and the muscle of sheep. Thus, the objective of this study was to evaluate the effect of the variation of rumen cellulolytic bacteria on the rumen fermentation, rumen digesta, and muscle FA composition of fattening lambs fed an identical diet. Forty-eight lambs were reared in individual units and fed a high-concentrate diet consisting of 20% forage and 80% concentrate. All lambs were adapted to diets and facilities for 14 d, and sampling was for 63 d. At the end of the experiment, the rumen fluid, rumen digesta, and longissimus dorsi were collected after slaughter for the measurement of volatile fatty acids, ruminal bacterial DNA, rumen digesta, and muscle FAs. The lambs were classified into the lower cellulolytic bacteria (LCB, n = 10) group and the higher cellulolytic bacteria (HCB, n = 10) group according to the abundance of pH-sensitive cellulolytic bacteria (Ruminococcus albus, Ruminococcus flavefaciens, Fibrobacter succinogenes, and Butyrivibrio fibrisolvens) in the rumen. Ruminal acetate concentration was positively correlated with the number of R. flavefaciens, F. Succinogenes, and B. fibrisolvens (P < 0.05, r > 0.296), whereas propionate and valerate concentrations were negatively correlated with the amount of F. succinogenes and B. fibrisolvens (P < 0.05, r > 0.348). Compared with the LCB group, the acetate (P = 0.018) as well as acetate to propionate ratio (P = 0.012) in the HCB group was higher, but the valerate ratio was lower (P = 0.002). The proportions of even-chain FAs and odd- and branched-chain fatty acid in the rumen digesta of lambs with the HCB were higher (P < 0.05), while the polyunsaturated fatty acids decreased than those in the LCB lambs (P < 0.05), but those FA proportions in the meat were similar between the two groups. The proportion of C17:0 in the meat of lambs in the HCB group was lower than that of lambs in the LCB group (P = 0.033). The proportions of conjugated linoleic acid in rumen digesta and meat were both higher in the HCB group than that in the LCB group (P = 0.046). These results indicated that the ruminal cellulolytic bacteria can alter the FA compositions in rumen digesta and further influenced the FA compositions in the meat of sheep.