Effects of branched-chain volatile fatty acids supplementation on growth performance, ruminal fermentation, nutrient digestibility, hepatic lipid content and gene expression of dairy calves

Abstract

This study evaluated the effects of branched-chain volatile fatty acids (BCVFA) supplementation on growth performance, ruminal fermentation, nutrient digestibility, hepatic lipid content and gene expression of dairy calves. Forty-eight Chinese Holstein male calves (10 months of age; 345 ± 6.4 kg of body weight [BW]) were assigned randomly to four treatments with 0, 60, 120 and 180 mg BCVFA per kg BW per day for each calf. Supplemental BCVFA was hand-mixed into the top third of the daily ration and fed to calves for 100 days to the experimental treatments. Supplementation of BCVFA in calves ration increased ADG and feed conversion linearly. Dry matter (DM) intake was unaffected, but digestibilitiy of DM, organic matter, crude protein, ether extract, neutral detergent fibre and acid detergent fibre increased linearly with increasing levels of BCFVA supplementation. Similarly, Supplementation of BCVFA linearly decreased ruminal pH and ammonia-N but increased total VFAs. Molar proportion of acetate linearly increased, whereas propionate linearly decreased and the ratio of acetate to propionate increased linearly with increasing BCVFA in rations. Relative mRNA expressions of peroxisome-proliferator-activated receptor α and carnitine palmitoyl transferase-1 linearly increased with BCVFA levels. The results suggested that BCVFA supplementation improved ruminal fermentation, nutrient digestibility and growth of calves with promoted hepatic lipid oxidation. Due to the unsignificant difference between 120 and 180 mg groups for all parameters, the optimum supplementary dose of BCVFA was 120 mg per kg BW per day.