Effects of including different energy sources in the diet supplemented with small peptides of cottonseed on in vitro rumen fermentation, digestibility and microbial enzymes activity

The aim of the present study was to investigate the effects of different sources of non-fibrous carbohydrates (NFC) in the dairy cow diet supplemented with small peptides of cottonseed (Fortide C) on in vitro ruminal gas production (GP), fermentation parameters, substrate disappearance and microbial enzyme activity. Four iso-energetic and iso-nitrogenous diets were fed, containing 1) maize, 2) barley, 3) wheat or 4) a maize+barley mixture as the main sources of NFC. Each diet was supplemented with 7.05 g Fortide C/kg dry matter (DM) and incubated with media containing rumen liquor for 96 h in vitro. Dietary supplementation of the Fortide C in the wheat grain diet yielded greater gas production (GP) at 16 h of incubation, total GP and potential GP (b) than those containing maize (P<0.05), but similar to barley-containing diet (P>0.05). Other GP parameters including GP at 24, 48 and 72 h of incubation and constant rate of GP (c) were similar among the experimental diets. The highest and lowest DM disappearance, apparently degraded substrates, organic matter disappearance, estimated metabolizable energy, short chain fatty acids and microbial protein synthesis (MPS) were observed in the Fortide C-supplemented wheat and maize diets, respectively (P<0.05). Using wheat in the diet decreased NH3-N compared to the maize diet (P<0.05). Inclusion of wheat in the diet supplemented with Fortide C increased carboxymethyl cellulase and α-amylase activities compared to the maize diet (P<0.05), while it was similar to the barley diet (P>0.05). However, microcrystalline cellulase and filter paper-degrading activities were unchanged among the dietary treatments. Overall, using wheat as the main source of NFC in the dairy cow diet supplemented with Fortide C improved in vitro ruminal fermentation profile, substrate disappearance, MPS and microbial enzyme activity compared to the maize or maize+barley-based diets.