Saturation Ratio of Supplemental Dietary Lipid on Production Performance of Holstein Cows

Two experiments were conducted to evaluate the effect of supplemental lipid varying in proportion of unsaturated and saturated fatty acids on lactation performance and milk composition. All diets (45% chopped alfalfa hay and 55% concentrates) contained 12% whole cottonseed(as-fed) and were fed as a TMR. Treatments were no supplemental lipid(control, 3% total fatty acids, DM basis) or the addition of 2% supplemental lipidfrom tallow, yellow grease, or a blend (60% tallow:40% yellow grease). In Exp.1, 48 cows were assigned to their treatment diets beginning wk 4 and ending wk 18 of lactation. In Exp. 2, 4 cowsthat completed Exp. 1 were enrolled in a4 × 4 Latin square with 2-wk periods to further study the effects of saturation ratioof the supplemental lipids on milk composition. In Exp. 1, no treatment effectswere observed for DMI, milk production, or milk composition; however, 4%fat-corrected milk tended to increase and fat yield increased for lipid-supplementedtreatments. In Exp. 2, DMI, milk production, and percent and yield of milk fat increasedin lipid-supplemented treatments.Digestible energy intakes tended to increase when yellow grease was the lipid source compared with tallow. In both experiments,milk fatty acid compositionwas affected by supplemental lipid as well as the source of supplemental lipid.No effects on lactation performance wereevident due to the differences in the unsaturated to saturated fatty acid composition of the supplemental lipid source.