Effects of high-roughage feeding on fattening performance, plasma concentrations of growth hormone (GH) and prolactin (PRL) in Japanese Shorthorn steers

Abstract

Effects of high-roughage feeding on fattening performance, plasma concentrations of GH and PRL were examined in Japanese Shorthorn steers. Japanese Shorthorn steers of 8 months of age were supplied formula and grass silage (formula group, n = 5) or corn silage and wheat bran (corn silage group : high-roughage feeding, n = 5), and the steers were fattened until 23 months of age. There was no significant difference in body weight (BW) through the experimental periods between corn silage and formula groups. Dry matter (DM) intake for 2 months after start of fattening was significantly higher in formula group than in corn silage group (P < 0.05). Total digestible nutrient (TDN) intake for 1 month and 11 to 14 months after start of fattening was significantly higher in formula group than in corn silage group (P < 0.05). Crude protein (CP) intake through the experimental periods was significantly higher in formula group than in corn silage group (P < 0.05). The plasma concentrations of GH were highest at the start of fattening and declined with advancing age ; however, there was no significant difference in GH concentrations between corn silage and formula groups. The plasma concentration of PRL changed seasonally in each group and showed high values in long photoperiod. The present results indicate that the differences in two feed types in this study affect DM, TDN and CP intake ; however, they do not affect BW and the plasma concentrations of GH and PRL. These results suggest that Japanese Shorthorn steers are superior to roughage availability.