Effects of Co-Products and Breed of Sire on the Performance, Carcass Characteristics, and Rates of Ultrasound Backfat and Marbling Deposition in Feedlot Cattle

Recently, high prices have driven producers to replace corn partially or totally with more affordable ingredients. A total of 1,256 DNA-validated progeny from Angus (n = 241), Simmental (n = 599), Simmental × Angus (SA; n = 296), and 75% Simmental (75S; n = 120) sires were used to evaluate the effects of feedlot nutrition and sire breed on the performance, carcass characteristics, and rates of ultrasound backfat and marbling deposition in feedlot cattle. Diets included corn or a corn co-product: dried distillers grains with solubles (DDGS), fresh wet distillers grains, wet corn gluten feed, stored wet distillers grains, or dried corn gluten feed. Dry matter intake for steers fed the co-product diets increased by approximately 8% compared with that of steers fed the high-corn diet. Steers fed the corn co-product diets had greater (P < 0.05) ADG. Steers fed DDGS, wet distillers grains, and wet or dried corn gluten feed deposited approximately 0.02 mm/d more (P < 0.05) backfat than steers fed the high-corn diet. The greatest (P < 0.05) rate of intramuscular fat deposition was in steers fed 40% DDGS. Steers sired by Angus bulls had greater (P < 0.05) DMI than the progeny of Simmental and SA sires. Backfat was greater (P < 0.05) in the progeny of Angus bulls than in the progeny of Simmental, SA, and 75S sires. Steers sired by Angus bulls had the greatest (P < 0.05) marbling score. The greatest rate (P < 0.05) of backfat deposition was observed in the progeny of Angus sires. Steers sired by Angus and SA bulls had the greatest rates (P < 0.05) of marbling deposition. The progeny of Simmental, Angus, and 75S were similar (P > 0.05) in the amount of marbling deposited per centimeter of backfat (184 marbling score units/cm of backfat). This study indicates that co-product diets had less effect on performance and carcass quality than did breed of sire.