The objective of this study was to evaluate the effects of isobutyrate supplementation on rumen microflora, enzyme activities and methane emissions in Simmental steers consuming a corn stover-based diet. Eight ruminally cannulated Simmental steers were used in a replicated 4 × 4 Latin square experiment. The treatments were control (without isobutyrate), low isobutyrate (LIB), moderate isobutyrate (MIB) and high isobutyrate (HIB) with 8.4, 16.8 and 25.2 g isobutyrate per steer per day respectively. Isobutyrate was hand-mixed into the concentrate portion. Diet consisted of 60% corn stover and 40% concentrate [dry matter (DM) basis]. Dry matter intake (averaged 9 kg/day) was restricted to a maximum of 90% of ad libitum intake. Population of total bacteria, cellulolytic bacteria and anaerobic fungi were linearly increased, whereas that of protozoa and total methanogens was linearly reduced with increasing isobutyrate supplementation. Real-time PCR quantification of population of Ruminococcus albus, Ruminococcus flavefaciens, Butyrivibrio fibrisolvens and Fibrobacter succinogenes was linearly increased with increasing isobutyrate supplementation. Activities of carboxymethyl cellulase, xylanase and β-glucosidase were linearly increased, whereas that of protease was linearly reduced. Methane production was linearly decreased with increasing isobutyrate supplementation. Effective degradabilities of cellulose and hemicellulose of corn stover were linearly increased, whereas that of crude protein in diet was linearly decreased with increasing isobutyrate supplementation. The present results indicate that isobutyrate supplemented improved microflora, rumen enzyme activities and methane emissions in steers. It was suggested that the isobutyrate stimulated the digestive micro-organisms or enzymes in a dose-dependent manner. In the experimental conditions of this trial, the optimum isobutyrate dose was approximately 16.8 g isobutyrate per steer per day.

SUMMARYThe objective of the present study was to evaluate the effects of isovalerate supplementation on growth performance and ruminal fermentation in pre- and post-weaning dairy calves. Forty-eight Chinese Holstein male calves at 15 days of age and 45·1 ± 0·36 kg body weight (BW) were assigned randomly to four groups. The treatments were: control, low-isovalerate, moderate-isovalerate (MIV) and high-isovalerate (HIV) with 0, 3, 6 and 9 g isovalerate per calf per day, respectively. Isovalerate was hand-mixed into milk in pre-weaning calves and the concentrate portion in post-weaning calves. The study lasted 75 days, including a 15-day adaptation period followed by a 60-day sampling period. Weaning was conducted when calves were 60 days old. Six calves were chosen from each treatment at random and slaughtered at 30 and 90 days of age. Average daily weight gain increased linearly whether during pre-weaning or post-weaning period with increasing isovalerate supplementation. Dry matter intake linearly increased at 90 days of age with increasing isovalerate supplementation. During weaning, ruminal pH and ammonia nitrogen (N) decreased linearly, whereas total ruminal volatile fatty acid concentration increased linearly with increasing isovalerate supplementation. The ratio of acetate to propionate increased linearly with increasing isovalerate supplementation due to increased acetate concentration and the unchanged propionate concentration. Activities of caboxymethyl-cellulase, cellobiase, xylanase and pectinase linearly increased at 90 days of age, α-amylase and β-amylase activities linearly increased at 30 and 90 days of age. Relative quantities of Butyrivibrio fibrisolvens, Ruminococcus albus, Fibrobacter succinogenes and Ruminococcus flavefaciens increased linearly with increasing isovalerate supplementation. Ruminal fermentation, enzyme activities and cellulolytic bacteria were higher for HIV and MIV than for the control. The present results indicate that isovalerate accelerated growth of calves by improving ruminal fermentation, microbial enzyme activities and cellulolytic bacteria growth during weaning. In the experimental conditions of the current trial, the optimum isovalerate dose was about 6·0 g isovalerate per calf per day.

The objective of the present study was to evaluate the effects of fibrolytic enzymes (FE, containing 160 units of cellulase and 4000 units of xylanase) or isobutyrate (IB) supplementation on ruminal fermentation, microbial enzyme activity and cellulolytic bacteria in dairy calves. Forty-eight Holstein bull calves of 15 days of age and of 44.9 ± 0.28 kg of BW were randomly assigned to four groups in a 2 × 2 factorial arrangement. Two levels of FE (0 g (FE–) or 1.83 g per calf per day (FE+)) and IB (0 g (IB–) or 6 g per calf per day (IB+)) were added. Calves were weaned at 60-day-old and four calves were selected from each treatment at random and slaughtered at 45 and 90 days of age. There was no IB × FE interaction effect. Ruminal pH decreased with IB or FE supplementation for post-weaned calves, whereas concentrations of total volatile fatty acids and acetate increased with IB or FE supplementation for pre- and post-weaned calves. Acetate to propionate ratio increased with IB supplementation, but was unaffected by FE supplementation. Ammonia-N concentration decreased with IB or FE supplementation for pre- and post-weaned calves. For post-weaned calves, activities of CMCase increased with IB or FE supplementation, and activities of cellobiase, xylanase, pectinase, β-amylase and protease increased with IB supplementation. Populations of B. fibrisolvens and F. succinogenes for pre- and post-weaned calves and R. flavefaciens for post-weaned calves increased with IB or FE supplementation. It is suggested that ruminal fermentation and growth performance of calves was improved with IB and FE supplementation, and the combination of IB and FE has the potential to stimulate the growth of pre- and post-weaned dairy calves.

Cellulose-degrading bacteria were identified from distillery lees, and the strains were optimized for fermentation and enzyme production, providing effective strains for the resource utilization of distillery lees and developing cellulase. Based on the univariate test, the response surface test was used to optimize enzyme production conditions for fermentation. The screened strain JZ2 had a clear circle-to-colony diameter ratio of 2.0. The enzyme activities of exoglucanase, endoglucanase, and β-glucosidase were 4.341 ± 0.05 U/mL, 1.874 ± 0.04 U/mL, and 0.739 ± 0.02 U/mL, respectively. The bacterial colonies were large, and the bacterial cells’ morphology was rod-shaped. We identified Bacillus cereus (JZ2) from 16S rDNA sequence homology and phylogenetic tree analysis as belonging to the genus Bacillus in the thick-walled Bacillus phylum. The optimum production conditions of cellulase from strain JZ2 were a fermentation time of 2 d, a rotation rate of 180× g, and a temperature of 26 °C using the response surface method. The enzyme activity of JZ2 was 4.625 U/mL under optimal enzyme production conditions. In addition to good activity, the cellulase from the JZ2 strain may have the potential to convert distillery lees cellulose into useful compounds.

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