Fernando Diaz
Ruminal branched-chain volatile fatty acids (BCVFA; isobutyrate, isovalerate, and 2-methylbutyrate) originates primarily from the degradation of branched-chain amino acids (valine, isoleucine, leucine and proline) included in the diet. Ruminal microorganisms utilize BCVFA as a source of carbon skeleton to synthesize branched-chain amino acids. Previous studies reported that dietary BCVFA supplementation enhance cellulolytic bacteria population and fiber digestibility in the rumen.
A recent study published in Animal Feed Science and Technology evaluated Branched-chain volatile fatty acids supplementation on ruminal fermentation and production performance of mid-lactation Holstein cows. The researchers (Wang et al., 2019) fed a TMR diet with or without 80 g of a BCVFA supplement composed of isobutyrate, isovalerate and 2-methylbutyrate (ratio of 1:1:1) top dressed daily.
The basal diet [(50% forage/50% concentrate in a dry matter (DM)] included ensiled corn forage without ears (25% DM), alfalfa hay (15% DM) and oat hay (10.0% DM) as forage sources, wheat bran as non-forage fiber (6.0% DM), ground corn (24% DM) for starch, Â soybean meal (10.6% DM), rapeseed meal (2.5% DM ) and cottonseed cake (5.0% DM) as protein supplements, and mineral and vitamins. Protein, neutral-detergent-fiber (NDF), Â acid-detergent-fiber (ADF), and non-fiber-carbohydrate (NFC) concentrations in the basal diet were 16.6, 40.3, 26.5, and 32.4% DM.
The researchers observed that ruminal microbial enzyme activity (cellulase, xylanase, pectinase, α-amylase and protease) as well as ruminal abundance (% of total bacterial) of the bacteria R. albus, R. flavefaciens, F. succinogenes, B. fibrisolvens and P. ruminicola were greater in the cows fed the BCVFA diet.
Moreover, molar proportion of acetate was increased (62.96 vs. 61.18 Mol/100 mol), and propionate molar proportion (18.39 vs. 20.83 Mol/100 mol) was decreased with BCVFA supplementation. Nutrient digestibility in the total tract was considerably higher in the BCVFA diet. Digestibility of DM, protein, NFC, NDF and ADF were increased by 3.4, 6.3, 6.5, 9.6 and 18.2%, respectively.
Feeding Branched-chain volatile fatty acids increased DM intake and milk yield. Compared with unsupplemented cows, cows receiving the additive consumed more (21.7 vs. 20.8 kg DM/day), produced more milk (32.5 vs. 28.9 kg/day), fat-corrected-milk (33.5 vs. 27.7 kg/day), milk fat (1.36 vs. 1.08 kg/day) and milk protein (1.09 vs. 0.91 kg/day). In addition, milk fat (4.19 vs. 3.73%) and milk protein concentration (3.34 vs. 3.16%) was higher in cows fed the folic acid diet.
In conclusion, these findings indicate that addition of branched-chain volatile fatty acids into lactation diets alters ruminal fermentation, and may improve nutrient digestibility and production performance.
Reference
Wang, Q. Liu, G. Guo, W.J. Huo, Y.L Zhang, C.X. Pei, S.L Zhang. 2019. Effects of rumen-protected folic acid and branched-chain volatile fatty acids supplementation on lactation performance, ruminal fermentation, nutrient digestion and blood metabolites in dairy cows.
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