Impact of feeding regimen on hip height measures in feedlot steers.

摘要

A study using 112 (116 while on pasture) fall born steers calves was conducted to evaluate the effect of plane of nutrition on skeletal growth. All steers were fall born calves obtained from one genetic source, Stewart Ranch in Caddo, Oklahoma. This genetically uniform group represented a blend of Angus and Hereford breeding. The four treatment groups were feedlot (F), July feedlot (JF), October feedlot (OF), and warm season pasture (WP). The F treatment group was placed directly into the feedlot as calves in early May when the trial began. The JF group was rotated among cool season grass paddocks from the onset of the trial until early July, at which time they were placed into the same feedlot conditions as treatment F. The OF group was rotated among cool season grass paddocks from the onset of the trial until late September, at which time they were placed into the same feedlot conditions as treatment F and JF. The WP group was rotated among cool season grass paddocks until mid June, at which time they were rotated among warm season grass paddocks until mid August when they were returned to the cool season grass paddocks until late September. Once removed from pasture in late September they were placed into the same feedlot conditions as treatments F, JF, and OF. Performance data was collected every 28 days which consisted of a hip height (HH) measurement and weight (WT). In addition, complete carcass data was collected at the time of harvest and feed consumption was recorded daily while steers were in the feedlot. Treatment groups were harvested at common end weights and similar degrees of maturity. Results show that an increased energy intake leads to a faster increase in HH and WT growth, along with the ratio of WT:HH. Also there was no indication of treatment differences between OF and WP. Most importantly, there was no difference in the end point values of HH and WT between any treatments among the two measured traits or their ratios. These findings suggest that reduced energy intake does not lead toward increased skeletal growth during any stage of the growing phase or at a common stage of maturity. By evaluating the ratio of WT:HH, results indicate that there is an effect on body mass brought about by energy intake. At no similar points in the growth curve does any treatment exceed the F treatment in HH, nor does JF ever get exceeded by the OF and WP treatments in HH growth. The increase rate of ratio change in the F treatment compared to all other treatments, the intermediate change represented by the JF, and the depressed rate of change represented by treatments OF and WP, suggests that with an increase in energy intake there is a greater increase in WT gain in relationship to HH gain. These results indicate that nutritionally cattle can be altered in their pathway to a common end mature weight. But, more importantly, reduced energy intake does not lead toward increased skeletal size at any point during the growing phase nor does this management practice produce a larger animal at a common end point with respect to weight and visual appraisal of degree of finish.