Effects of the Use of Rice Grain on Growth Performances, Blood Metabolites, Rumen Fermentation, and Rumen Microbial Community in Fattening Hanwoo Steers.

This study aimed to assess the influence of rice grain in the total mixed ration (TMR) on the growth performance, blood metabolites, rumen fermentation, and rumen microbial community of fattening Hanwoo steers. Two experimental diets were prepared: (i) a TMR containing 33% dry matter (DM) corn grains (Corn TMR) and (ii) a TMR containing 33% DM rice grains (Rice TMR). Twenty-two Hanwoo steers (body weight [BW], 498 ± 32 kg; months, 17 ± 0.5) were distributed into two treatment groups in a completely randomized block design according to BW. The Rice TMR group had a higher final BW and DM intake (DMI) compared to those in the Corn TMR group ( p < 0.01). However, no difference was observed in the average daily gain (ADG) and feed conversion ratio (FCR) between the two treatments. For the rumen fermentation parameters, the molar portion of butyrate in the Rice TMR was higher than in the Corn TMR ( p < 0.01). Streptococcus bovis tended to be higher in the Rice TMR ( p = 0.09). The results of this study suggest that using rice grain as the primary starch source in TMRs may be an alternative option for fattening Hanwoo steers.