Effects of supplemental fat on growth performance and quality of beef from steers fed corn finishing diets

¹ Department of Animal Sciences, Washington State University, Pullman 99164-6351
² Food Science and Human Nutrition, Washington State University, Pullman 99164-6351

^* To whom correspondence should be addressed. E-mail: nelsonm{at}wsu.edu.

	Abstract

To measure effects of dietary fat on feedlot performance, carcass characteristics, and beef appearance, moisture binding, shelf life, palatability and fatty acid content, 126 crossbred beef steers (321.1 ± 0.57 kg) were allotted to a randomized complete block (3) design with a 3 x 2 + 1 factorial arrangement of dietary treatments. Main effects were level of yellow grease (0, 3 or 6%) and alfalfa hay (3.5 or 7%) in corn-based diets containing 15% potato byproduct (PB). The added treatment was 6% tallow and 7% alfalfa in a barley-based diet containing 15% PB. Dry matter intake and ADG were not affected by diet, however G/F and diet NE content increased linearly (P < 0.10) with yellow grease. Kidney, pelvic, and heart fat (2.0 to 2.3 ± 0.07) and yield grade (2.8 to 3.1 ± 0.09) increased linearly (P < 0.05) with yellow grease. Corn plus 6% yellow grease fed steers had lower (P < 0.05) beef firmness and beef texture scores but greater (P < 0.01) fat color score than those fed barley plus 6% tallow. Moisture retention of beef was not affected by dietary treatment except purge score during retail storage which was decreased linearly (P < 0.01) from 2.1 to 1.6 ± 0.06 by level of yellow grease. Steaks from barley plus 6% tallow-fed steers had greater (P < 0.05) shear force than those from steers fed corn plus 6% yellow grease and beef flavor increased linearly (P < 0.05) from 6.2 to 6.7 ± 0.11 as yellow grease increased. Level of yellow grease increased linearly (P < 0.01) transvaccenic acid (TVA) by 61% and CLA content of beef by 48%. Beef from corn plus yellow grease-fed steers had lower (P < 0.05) palmitoleic and oleic acids and greater (P < 0.05) linoleic, TVA, and CLA than beef from barley-tallow fed steers. Feeding yellow grease increased diet energy content which increased carcass fatness, altered beef fatty acid content which increased beef flavor without affecting moisture retention, shelf-life, or cooking properties of the beef. Additionally, beef from corn plus 6% yellow grease-fed steers was more tender and had more polyunsaturated fatty acid content and CLA than of beef from barley plus 6% tallow-fed steers.

Key Words: beef cattle, CLA, fatty acid, transvaccenic acid, yellow grease