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Title: EFFECTS OF SUPPLEMENTAL PROTEIN TYPE ON INTAKE, NITROGEN BALANCE, AND SITE, AND EXTENT OF DIGESTION IN WHITEFACE WETHERS CONSUMING LOW-QUALITY GRASS HAY

Author
item SALISBURY, M - ANGELO STATE UNIV
item KREHBIEL, C - OKLAHOMA STATE UNIV
item ROSS, T - NEW MEXICO STATE UNIV
item Schultz, Carrie
item Thornton, Laura

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2004
Publication Date: 12/1/2004
Citation: Salisbury, M.W., Krehbiel, C.R., Ross, T.T., Schultz, C.L., Thornton, L.L. 2004. Effects of supplemental protein type on intake, nitrogen balance, and site, and extent of digestion in whiteface wethers consuming low-quality grass hay. Journal of Animal Science. 82(12):3567-3576.

Interpretive Summary: Providing a protein supplement to lambs on low quality feed increased intake and nitrogen balance. Even though the quality of feed may be low, where a protein supplement is fed, adverse reactions to animal performance can be minimized. The financial implications of this study are to illustrate that low quality feed can be used with a supplemental feed with adequate animal growth and performance. This is particularly important in drought stricken areas where high quality feed is scarce for range animals.

Technical Abstract: Two experiments were conducted to determine the effects of supplementing ruminally degradableintake protein (DIP) or ruminally undegradable intake protein (UIP) on N balance (Exp. 1; n = 6 wethers; initial BW = 48.7 +- 4.6 kg) and site and extent of digestion(Exp. 2; n = 5 wethers; initial BW = 36.9 +- 3.1 kg)in whiteface wethers consuming 69% blue grama and 31% love grass hay (mixture = 7.5% CP, 73.0% NDF, 36.0% ADF [DM basis]). Treatments were 1) no supplement (Control), 2) a supplement (219 g/d, as-fed basis) low in UIP (70 g/d of CP; 24.8 g/d of UIP), and 3) a supplement (219 g/d, as-fed basis) high in UIP (70 g/d of CP; 37.1 g/d of UIP). Both experiments were replicated 3 × 3 Latin square designs, with identical feeding and supplementation. Wethers had ad libitum access to the forage mixture and fresh water, and received supplement once daily. In Exp.1, forage intake (percentage of BW) was greatest (P = 0.04) for control,but total DMI (g/d) was greatest (P = 0.05) for lambs consuming supplement. Apparent total-tract OM digestibility was numerically greater (P = 0.11) for supplemented wethers than for controls, whereas totaltract ADF digestibility tended (P = 0.08) to be greater for control wethers. Lambs fed supplements consumed between low and high UIP treatments. Similar to Exp. 1, forage intake (percentage of BW) tended (P = 0.06) to be greater for control than for supplemented wethers in Exp. 2. Ruminal NDF digestibility was 16.3% greater (P = 0.02) for supplemented wethers than for controls. Postruminal NDF and N digestibilities were greatest (P <= 0.03) for controls, but apparent OM digestibility did not differ among treatments at all sites. Duodenal N flow was greatest (P = 0.05) for high UIP and least for control wethers. Nonmicrobial N flow was greater (P = 0.02) for high UIP compared with low UIP or controls. Control wethers had greater (P = 0.05) microbial efficiency. Ruminal ammonia concentration tended (P = 0.08) to be greatest for wethers fed low UIP and least for controls, with high-UIP wethers having intermediate ammonia concentrations. Results from these experiments suggest that in lambs fed low-quality forage there was no difference in apparent total-tract digestion or N balance (percentage of N intake) between lambs fed supplements that had the same CP but differed in the proportion of UIP and DIP; however, supplementing protein (regardless of UIP:DIP ratio) to wethers consuming low-quality forage increased N balance.