Authors : L. Corona , A. Plascencia , R. A. Ware and R. A. Zinn
Abstract: Four Holstein steers (456 kg) fitted with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square design to evaluate the influence of substituting palmitic acid (Energizer?, IFFCO, EEU; 92% C16:0) for conventional feed fat (yellow grease) on characteristics of digestion and utilization of fat. Treatments were: 1) basal diet, no supplemental fat; 2) 5% of yellow grease; 3) 2.5% of yellow grease and 2.5% palmitate and 4) 5% palmitate. The basal diet contained (DMB): alfalfa hay (40.0%), steam-flaked corn (43.2%), canola meal (7.0%), molasses (8.0%) , and mineral supplement (1.8%). Fat treatments replaced steam-flaked corn in the basal diet. Total fatty acid intake for fat supplemented diets averaged 637 g/d. Inclusion of palmitate increased quantitatively (linear effect, P < 0.01) the flow of palmitate to the small intestine . Ruminal biohydrogenation of unsaturated dietary fat averaged 67%. Based on fatty acid intake (fatty acid g/kg of BW), observed intestinal fatty acid digestion for yellow grease, blend of yellow grease and palmitate-, and palmitate-supplemented diets were 1.00, 1.06 and 1.02 of expected. Ruminal and total tract digestion of OM was not affected (P > 0.20) by fat supplementation. Fat supplementation increased (P < 0.05) ruminal digestion of NDF, and ruminal and total tract digestion of N. Fat supplementation decreased (P < 0.05) ruminal microbial efficiency (g microbial N/kg OM fermented), and protein efficiency (N flow to the small intestine/N intake). Substitution of yellow grease for palmitate increased (linear effect, P < 0.10) intestinal digestion of OM and NDF. There were no treatment effects (P > 0.20) on ruminal pH, VFA molar proportions, or estimated methane production. Calculated NEg for supplemental fats were 4.53 ,4.83, and 4.64 Mcal/kg for yellow grease, yellow grease-palmitate blend, and palmitate, respectively. Intestinal digestion of a supplemental fat consisting of 92% palmitate is equivalent to that of yellow grease (conventional feed fat). Substituting a portion of the supplemental feed fat with palmitate may have a positive associative effect on intestinal fat digestion.
L. Corona , A. Plascencia , R. A. Ware and R. A. Zinn , 2005. Comparative Feeding Value of Palmitate as a Substitute for Conventional Feed Fat in Cattle . Journal of Animal and Veterinary Advances, 4: 247-253.