Effects of added protein and dietary fat on lamb performance and carcass characteristics when fed differing levels of dried distiller's grains with solubles

Abstract

The objectives of this study were to evaluate the influence of dietary protein and fat in dried distiller's grains with solubles (DDGS) on feedlot performance and carcass characteristics finishing lambs. Sixty crossbred lambs (29.16±4.59kg) were allotted into pairs (ewe and wether; 6 pairs/trt) and fed one of five isocaloric dietary treatments: (1) a corn based diet with DDGS included to meet CP requirements (∼25% of DM; CON), (2) CON with DDGS included at twice the amount of CON (∼50% of DM; 50DDGS), (3) CON with added corn protein in the form of gluten meal to be similar of CP in the 50DDGS diet (CON+CP), (4) CON with added vegetable oil to be similar to the crude fat in the 50DDGS diet (CON+VO), and (5) CON with corn protein and vegetable oil added to be similar to the CP and crude fat in the 50DDGS diet (CON+CPVO). Wether lambs were harvested when they obtained a common 12th rib fat depth endpoint of 0.5cm. Ewe lambs were returned to the flock. Data were analyzed using the MIXED procedure of SAS. Contrasts between (1) CON vs. elevated CP diets (50DDGS, CON+CP, and CON+CPVO; PRO), (2) CON vs. elevated fat diets (50DDGS, CON+VO, and CON+CPVO; FAT) and (3) CON vs. diets with both elevated CP and fat (50DDGS and CON+CPVO; PF) were analyzed. Final BW, days on feed, and G:F did not differ as a result of dietary treatment (P≥0.29). However, DMI was decreased (P=0.03) in the lambs fed PRO diets compared with CON fed lambs. Average daily gain tended (P=0.08) to decrease in the lambs fed the PRO diets compared with the lambs fed CON. Lambs did not differ (P>0.05) in HCW, dressing percentage, 12th rib fat depth, LM area, body wall thickness, yield grade, flank streaking, leg score, percent boneless, closely trimmed retail cuts, and LM ether extract. Therefore, these data indicate that DDGS can be included in feedlot lamb diets at levels up to 50% of DM without negatively affecting feedlot performance, carcass quality, and metabolite concentrations.