|Galloway Sr, D - UNIV OF ARKANSAS|
|Hallford, D - NEW MEXICO STATE UNIV|
Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 4, 1995
Publication Date: N/A
Interpretive Summary: Supplementation during growing with rumen undegradable protein (RUP), which increased the quantity of protein in the empty body without markedly affecting fat deposition, decreased finishing live weight gain, associated with loss of improvement in protein deposition during growing. The increase in mass of protein in the empty body after supplementation with maize during growing was not diminished greatly during finishing, and the increase in empty body fat mass after finishing was slightly greater than after growing. These changes appeared consequences of a stimulatory effect of altered body composition and associated physiological conditions due to supplementation with maize during growing on subsequent feed intake and nutrient metabolism. Overall, effects of supplementation with maize and RUP on growing and subsequent finishing performance and body composition were additive. These results suggest that the decision as to whether to supplement moderate- to low-quality grass with a cereal grain, RUP or both during growing should be based primarily on supplement cost if sale price is based on live weight after growing. However, with retained ownership and finishing for a set period of time, supplementation with cereal grain during growing may be more profitable than supplementation with RUP. But, if body composition after finishing is of concern, then potential for increased fat and decreased protein concentration in the empty body after finishing elicited by prior maize supplementation should be considered.
Technical Abstract: Crossbred wethers (80, 4 mo of age and 25 +/- 0.2 kg) were used to determine effects of supplementing moderate-to low-quality forage with ground maize (M; 0.7% body weight), a mixture of feedstuffs high in rumen undegradable protein (R; 0.2% body weight) or M plus R on growing (70 d) and subsequent finishing (98 d; 85% concentrate diet) performance and body composition. During growing, wethers consumed ad libitum bermudagrass (BER) or bromegrass (BRO) hay and 0.35% body weight of soybean meal. Empty body fat (4.28, 5.91, 5.20, 6.64, 4.18, 5.17, 4.96, and 6.20 kg; SE 0.357) and protein (4.45, 5.02, 5.05, 5.32, 4.57, 4.84, 4.93, and 5.21 kg for BER-Control, BER-M, BER-R, BER-MR, BRO-Control, BRO-M, BRO-R, and BRO-MR, respectively; SE 0.074) after growing were increased (P<0.05) by supplementation with M or R. Finishing live weight gain (195, 199, 174, 186, 217, 218, 191, and 204 g/d; SE 6.7) was depressed (P<0.05) by supplementation with R, and empty body fat (14.0, 16.3, 14.2, 17.5, 14.7, 16.0, 14.7, and 16.7 kg; SE 0.936) and protein (6.65, 6.92, 6.62, 7.07, 6.78, 6.88, 6.82, and 7.00 kg for BER-Control, BER-M, BER-R, BER-MR, BRO- Control, BRO-M, BRO-R, and BRO-MR, respectively; SE 0.093) after finishing were increased (P<0.05) by M supplementation. In summary, supplementation with R during growing decreased finishing live weight gain, which was accompanied by loss of improvement in protein deposition achieved during growing. Conversely, the increase in empty body protein after supplementation with maize during growing was not greatly diminished during finishing, and the effect on empty body fat was slightly greater after finishing than before.