Effects of different forages and kenaf silage on in vitro rumen fermentation and growth performance of Hanwoo steer.

The present study evaluated the feed value of a new forage resource, kenaf, for the ruminant animal. Rumen fermentation characteristics and digestibilities of kenaf (K) and its silage (KS) were compared with those of rice straw (RS) and ryegrass (RG) in an in vitro study. The effects of KS feeding on growth performance of Hanwoo steer were also investigated. In vitro rumen fermentation using 0.5 g of dried and ground forage and 50 mL of rumen inoculum was performed for 72 hours. For rumen fermentation characteristics, total gas production of KS was significantly higher than that of others at 48 h. Gas productions of RG and K were significantly higher than others at 72 h. Ammonia nitrogen did not differ among groups at both of 48 and 72 h. For IVDMD, K showed significantly higher values than others at 48 h (P < 0.05). At 72 h, RG and K showed significantly greater IVDMD than the others treatments (P < 0.05). No difference between RG and K for IVDMD was found. Total volatile fatty acid and acetate production were significantly higher in the order of K > RG > KS > RS, regardless of incubation time (P < 0.05). In propionate production, RG was significantly higher than others at 48 and 72 h (P < 0.05). Thirty-six Hanwoo steers were assigned into three groups (RS, RG, and KS) based on a complete randomized design for a feeding trial. Growth performances were measured for 172 days. During the early period (0 ~ 43 days), average daily gain (ADG) of K was significantly lower than that of other treatments (P < 0.05). However, during the following days, no significant differences in ADG between groups were detected. At the end of trial, a significantly decreased feed requirement (feed/gain) was found in the KS group (P < 0.05). In conclusion, results of ruminal fermentation characteristics and feeding trial showed that kenaf and its silage can be used as forage resource for ruminants, and these resources could be beneficial for farm in terms of nutrition for animal and economics for farm. [ABSTRACT FROM AUTHOR]