PSXII-17 Fiber content in diets for feedlot lambs: carcass characteristics

Abstract

Abstract The objectives of this trial were to evaluate the effects of levels of fiber in high-grain diets on carcass characteristics of feedlot lambs. Fifty-eight Dorper x Santa Inês ram lambs (initial BW 20.7 ± 1.19 kg and 75 ± 10.83 d old) were assigned to a randomized complete block design. The treatments were defined by the fiber (“Coastcross” hay) content in the diets (CP: 16,12% ± 0.92): 0F: no forage diet (NDF: 10.4%); 5F: 5% of forage (NDF: 12.1%); 10F: 10% of forage (NDF: 15.0%); 15F: 15% of forage (NDF: 15.5%); 20F: 20% of forage (NDF: 20.8%) and 25F: 25% of forage (NDF: 23.5%). The experiment lasted 89 days, at the end of this time, the animals were slaughtered (169 ± 10.83 d old) to evaluate carcass characteristics. There was a quadratic response for slaughter BW (0F: 46.3; 5F: 48.1; 10F: 49.4; 15F: 50.3; 20F: 48.5; 25F: 43.3 kg; P < 0.01), hot carcass weight (0F: 24.8; 5F: 25.6; 10F: 26.0; 15F: 25.7; 20F: 24.3; 25F: 21.8 kg; P = 0.01), cold carcass weight (0F: 24.3; 5F: 25.1; 10F: 25.4; 15F: 25.1; 20F: 23.8; 25F: 21.2 kg; P = 0.01) and longissimus dorsis area (0F: 16.3; 5F: 16.5; 10F: 17.4; 15F: 16.5; 20F: 16.0; 25F: 15.1 cm2; P = 0.04). There was a linear decrease in the hot carcass yield (0F: 53.0; 5F: 53.3; 10F: 52.5; 15F: 50.9; 20F: 50.1; 25F: 50.2%; P < 0.01), cold carcass yield (0F: 52.0; 5F: 52.2; 10F: 51.4; 15F: 49.8; 20F: 49.0; 25F: 48.9%; P < 0.01) and body wall thickness (0F: 16.2; 5F: 17.0; 10F: 16.3; 15F: 16.3; 20F: 15.1; 25F: 13.6 kg; P = 0.01). There was no effect on subcutaneous fat thickness. In conclusion, the diet with up to 5% of forage allowed higher carcass yield; however, the heavier carcasses were produced by the lambs that received 10F diet.