Palmitic acid increased yields of milk and milk fat and nutrient digestibility across production level of lactating cows

Abstract

The effects of palmitic acid supplementation on feed intake, digestibility, and metabolic and production responses were evaluated in dairy cows with a wide range of milk production (34.5 to 66.2kg/d) in a crossover design experiment with a covariate period. Thirty-two multiparous Holstein cows (151±66 d in milk) were randomly assigned to treatment sequence within level of milk production. Treatments were diets supplemented (2% of diet DM) with palmitic acid (PA; 99% C16:0) or control (SH; soyhulls). Treatment periods were 21 d, with the final 4 d used for data and sample collection. Immediately before the first treatment period, cows were fed the control diet for 21 d and baseline values were obtained for all variables (covariate period). Milk production measured during the covariate period (preliminary milk yield) was used as covariate. In general, no interactions were detected between treatment and preliminary milk yield for the response variables measured. The PA treatment increased milk fat percentage (3.40vs.3.29%) and yields of milk (46.0vs. 44.9kg/d), milk fat (1.53vs.1.45kg/d), and 3.5% fat-corrected milk (44.6vs. 42.9kg/d), compared with SH. Concentrations and yields of protein and lactose were not affected by treatment. The PA treatment did not affect dry matter (DM) intake or body weight, tended to decrease body condition score (2.93vs. 2.99), and increased feed efficiency (3.5% fat-corrected milk/DM intake; 1.60vs.1.54), compared with SH. The PA treatment increased total-tract digestibility of neutral detergent fiber (39.0vs.35.7%) and organic matter (67.9vs.66.2%), but decreased fatty acid (FA) digestibility (61.2vs.71.3%). As total FA intake increased, total FA digestibility decreased (R2=0.51) and total FA absorbed increased (quadratic R2=0.82). Fatty acid yield response, calculated as the additional FA yield secreted in milk per unit of additional FA intake, was 11.7% for total FA and 16.5% for C16:0 plus cis-9 C16:1 FA. The PA treatment increased plasma concentration of nonesterified FA (101vs.90.0μEq/L) and cholecystokinin (19.7vs. 17.6pmol/L), and tended to increase plasma concentration of insulin (10.7vs. 9.57μIU/mL). Results show that palmitic acid fed at 2% of diet DM has the potential to increase yields of milk and milk fat, independent of production level without increasing body condition score or body weight. However, a small percentage of the supplemented FA was partitioned to milk.