Effect of nonfiber carbohydrate and crude protein levels in the formula of feed on in vitro rumen fermentation characteristics and growth performance of weaned Hanwoo calves

Abstract

This study was conducted to determine the effect of nonfiber carbohydrates (NFC) and crude protein (CP) present in formula feed on the rumen fermentation characteristics and growth performance of weaned Hanwoo calves. Forty weaned calves were randomly assigned to four dietary groups based on NFC and CP levels as follows: high NFC (HN) at 38%-42%, low NFC (LN) at 33%-36%, high CP (HP) at 25%-26%, and low CP (LP) at 23%-24%. These groups were categorized as HN-HP, HN-LP, LN-HP, and LN-LP groups. Total digestible nutrients (TDN) and CP levels did not significantly affect the in vitro ruminal total gas, propionate, acetate, and NH$_{3}$-N concentrations after 12 h of incubation. Butyrate concentration was significantly higher in the LN-LP group than in the HN-HP group after 6 h of incubation (p < 0.05). Neutral detergent fiber degradability was significantly lower in the LN-LP group than in the HN-HP group (p < 0.05). The varying CP and NFC levels of formula feed did not significantly affect the growth performance of Hanwoo calves. Therefore, HN and HP levels of formula feed had no significant effect on rumen fermentation and growth performance. In summary, these results suggest that NFC at 33% and CP at 23% in formula feeds are sufficient in satisfying the energy and protein requirements of weaned Hanwoo calves.