Submitted to: Livestock Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/1998
Publication Date: N/A
Citation: N/A Interpretive Summary: The use of oilseeds in diets of lactating dairy cows results in a reduction of milk protein. In a controlled intake experiment with young growing beef steers, a diet supplemented with roasted soybeans was shown to reduce average daily gain and depress the release of growth hormone, suggesting the additional oil may negatively effect protein production via effects on the hypothalamic axis. This study was conducted to determine if the same effects of feeding roasted soybeans occurs under feedlot conditions. There were no differences in dry matter and protein digestibilities or N balance obtained. The results were not consistent with the controlled intake experiment. They suggested an improvement in performance under feedlot conditions when RSB replaces soybean meal in the diet of beef cattle not implanted. Furthermore, with an estrogenic growth promoter, this advantage for RSB is not realized. This study also points out the limitations in extrapolating results from controlled intake studies to the production situations.
Technical Abstract: Twenty Angus-Hereford steers (216+5 kg BW) and 20 Angus-Hereford heifers (208+5 kg) were used to investigate the individual and combined effects on performance under ad libitum intake feedlot conditions of supplementing diets with roasted soybeans (RSB, roasted at 127§ C for 10 min) compared with soybean meal and implanting or not implanted with an estrogenic growth promoter (SYN; Synovex-S, 20 mg estradiol benziate plus 200 mg progesterone and Synovex-H, 20 mg estradiol Benzoate plus 200 mg testosterone). Four Angus-Hereford steers were used in a digestion and nitrogen balance experiment to estimate possible differences in diet utilization. The feedlow experiment was a 150-d trial divided into 75-d periods and fed a basic diet of 15% orchard grass silage, 15% corn silage, and 70% corn-based concentrate. Treatments were 1) no SYN and fed a soybean meal supplemented diet, 2) no SYN and fed a RSB-supplemented diet, 3) plus SYN and soybean meal,and 4) plus SYN and RSB. For treatments 1,2,3, and 4, respectively, final BW were 443, 452, 495, and 464 kg (SYN,P< .01;RSB by SYN, P<.10; SEM=10 kg),DM intake were 8.6, 8.0, 9.2, and 8.4 kg (RSB,P<.10;SEM=10 kg),ADG were 1.37, 1.42, 1.64, and 1.50 kg (SYN,P< .05;SEM=.04 kg), and gain/DM intake were 160, 179, 183, and 179 (SYN,P<.05;RSB,P<.01;RSB by SYN,P<.05;SEM=1.4 g/kg). There were no differences in digestibilities or N balance obtained.