Vet Column 4-5-10
Fort Collins, Colo.
Potential finishing performance of feeder cattle can be affected by previous plane of nutrition, body composition, body weight, age and breed type. In order to achieve adequate frame size before entering the finishing phase, weaned calves are often placed into a backgrounding or stocker program. Some cattle, however, go directly to finishing after weaning. Investigators from Oklahoma State University and Colorado State University recently published data describing the effects of a winter growing program on subsequent finishing performance, carcass merit, and body composition.
Steers that are fed to have greater rates of body weight gain during backgrounding are fatter for all measures of carcass composition upon feedlot entry compared with steers that have been nutritionally restricted. Rate of body weight gain during finishing can be influenced by plane of nutrition and energy density of the diet during the growing phase. This experiment was designed to examine varying rates of fat accumulation during backgrounding, but similar body weight gain, upon performance during the finishing phase.
British crossbred steers (260 head) were utilized in this project. Varying diets fed post-weaning involved free access to a high concentrate diet; grazing on wheat pasture with unrestricted forage availability; a sorghum silage-based growing diet; and a controlled access, high concentrate diet.
Feeder cattle that are fatter typically garner price discounts compared with leaner cattle because of expected decreased performance and efficiency during the finishing phase. It has been shown in other studies that calves exhibiting greater fat composition at feedlot entry did not have reduced finishing average daily gain or feed efficiency compared with calves with less fat composition at feedlot entry.
Results from this study indicate that calves fatter at feedlot entry had improved finishing average daily gain and feed efficiency compared with calves that were leaner at feedlot entry. The present study also found that calves fatter at feedlot entry had greater gains of carcass protein and energy during the finishing phase. Also, increasing grain content of the growing diet resulted in greater fat content of the empty body.
Conclusions from this study indicate that growing programs which increase body fat composition will not negatively affect subsequent feedlot performance and efficiency. When fed to a common 12th-rib fat end point, growing programs that alter body composition before finishing will not significantly alter carcass quality or body composition at final slaughter.
When comparing the option of feeding calves at weaning in the feedlot through finishing without a backgrounding phase, final carcass composition and carcass quality may not be necessarily improved as compared with calves placed on a growing diet before finishing. Similarly, calf-fed steers may not be more energetically efficient during finishing than steers previously backgrounded. This study would indicate that one approach is not necessarily better than the other.
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