Source of dietary lipid may modify the immune response in stressed feeder cattle

¹ Department of Animal Sciences and Industry, Kansas State University, Manhattan, KS 66506-1600
² USDA, Agricultural Research Service, Beltsville, MD 20705
³ Department of Statistics, Kansas State University, Manhattan, KS 66506-1600

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

	Abstract

Five studies were conducted to evaluate the effects of lipid source on performance and health. A total of 332 heifers (195 ± 2.37 kg initial BW) in Trial 1 and 336 heifers (206 ± 1.70 kg initial BW) in Trial 2 were fed diets containing ground flaxseed (FLAX), rolled full-fat soybeans (SOY), or tallow (TAL) at 13, 20, or 4%, respectively (DM basis). All diets were formulated to be iso-nitrogenous and iso-caloric. The ADG and feed efficiency for the first 7 d and for the entire feeding period were greater (P < 0.05) for TAL and FLAX than for SOY. Percentage of animals treated and re-treated for bovine respiratory disease did not differ among dietary treatments. The FLAX treatment increased (P < 0.05) total n-3 polyunsaturated fatty acid (PUFA) concentrations in the plasma, whereas SOY increased (P < 0.05) plasma concentrations of total n-6 PUFA. In Trial 3, 18 steers were individually fed diets containing tallow (TAL) and 18 steers were fed a diet containing rolled full-fat soybeans (SOY; 20% of DM). In Trials 4 and 5, 18 steers were individually fed diets containing tallow (TAL) and 18 steers were fed diets containing ground flaxseed (FLAX; 12.9% of DM). On d 14 and 17 of study 3, 4, and 5, 16 steers from each dietary treatment were injected i.v. with E. coli O55:B5 lipopolysaccharide (LPS), and 2 steers from each diet were injected with saline. Rectal temperatures after LPS challenge were lower (P < 0.05) for SOY and FLAX than for TAL, and plasma TNF was greater (P < 0.05) for SOY than for TAL. Serum haptoglobin and blood fibrinogen increased and white blood cell count decreased in response to LPS, but none of these variables were affected by treatment. Although this research failed to measure a response of lipid source on feedlot morbidity or mortality, these studies indicate that altering the source and type of dietary fatty acids may modify the immune response in stressed feeder cattle, and that performance may be hindered by feeding full-fat soybeans to receiving cattle.

Key Words: endotoxin challenge, immune modulation, lipids, receiving cattle, plasma lipid