Utilization of Grass Silage by Growing Cattle: Effect of a Supplement Containing Ruminally Protected Amino Acids

Source: D. M. Veira, J. R. Seoane and J. G. Proulx
Sixteen crossbred steers (278 +/- 4.9 kg) were used to determine the influence of supplemental ruminally protected lysine and methionine on performance of growing cattle fed grass silage. During the 154-d experiment, all steers were allowed ad libitum consumption of a good-quality grass silage during the hrst 70 d and of a lesserquality silage during the remaining 84 d of the trial. The steers received a supplement of .5 kg/d of barley with or without a mixture of ruminally protected amino acid (RPAA) containing 8.2 g of lysine and 2.6 g of methionine. Compared with controls, steers supplemented with RPAA showed 16.3% improved (P < .03) ADG (.92 vs 1.07 kg/d). Dry matter intake was not affected (P > .50) by treatment and averaged 2.03% BW across treatments. Supplementation with RPAA improved fedgain by 13.6% (7.88 vs 6.81 for control and RPAA treatments, respectively, P < .01). Plasma levels of methionine, lysine, arginine, and glutamic acid were higher (P < .05) and of histidine were lower (P < .001) when RPAA were fed These results indicate that feeding RPAA can improve the performance of growing steers fed grass silages of varying qualities.