Altering the ratio of palmitic, stearic and oleic acids in diets with or without whole cottonseed impacts production responses and energy partitioning of dairy cows

Abstract Text:

We evaluated the effects of varying the ratio of dietary palmitic (C16:0), stearic (C18:0), and oleic (cis-9 C18:1) acids in diets with or without whole cottonseed on nutrient digestibility and production response of dairy cows. Twenty-four mid-lactation Holstein cows were used in split plot Latin square design. Cows were allocated to a main plot receiving either a basal diet without whole cottonseed (SH, n=12) or a basal diet with whole cottonseed (CS, n=12; 8% diet DM). Within each plot a 4×4 Latin square arrangement of treatments was used in four consecutive 21-d periods. Fatty acid (FA) treatments were: 1) Control (CON; no supplemental fat); 2) C16:0 supplement (PA; ~80% C16:0); 3) C16:0 and C18:0 supplement (PA+SA; ~40% C16:0 + ~40% C18:0); and 4) C16:0 and cis-9 C18:1 supplement (PA+OA; ~45% C16:0 + ~35% cis-9 C18:1). The final 5 d of each period were used for sample and data collection. The statistical model included the random effect of cow and the fixed effects of basal diet, FA treatment, period, and their interactions. Compared with SH diets, CS diets increased milk fat yield (1.71 vs. 1.51 kg/d; P=0.05), yield of preformed milk FA (623 vs. 507 g/d; P<0.01), and BW gain (1.0 vs. 0.71 kg/d; P=0.04), tended to increase yield of de novo milk FA (396 vs. 383 g/d; P=0.06), but reduced NDF digestibility (41.9 vs. 46.4%; P<0.01) and total FA digestibility (74.2 vs. 76.3% P=0.05). Compared with other treatments, PA increased yield of milk fat (1.60, 1.70, 1.64 and 1.64 kg/d; P<0.05) and 3.5% FCM (45.2, 47.8, 46.8 and 46.5 kg/d; P<0.01) for CON, PA, PA+SA and PA+OA, respectively. PA+OA increased BW gain compared with other treatments (0.82, 0.84, 0.70 and 1.05 kg/d; P<0.05) for CON, PA, PA+SA and PA+OA, respectively. PA and PA+OA tended to increase NDF digestibility compared with PA+SA and CON (43.2, 44.9, 43.1 and 44.5%; P<0.10) for CON, PA, PA+SA and PA+OA, respectively. Compared with the other treatments, PA+SA reduced 16-carbon (77.6, 73.0, 66.0 and 79.1%; P<0.01), 18-carbon (79.2, 79.5, 72.0 and 79.7%%; P<0.01), and total FA digestibility (78.6, 77.4, 68.2 and 79.4%; P<0.01) for CON, PA, PA+SA and PA+OA, respectively. In conclusion, diet inclusion of C16:0 increased energy output in milk, while inclusion cis-9 C18:1 increased BW gain. The combination of C16:0 and C18:0 reduced NDF and FA digestibilities, which likely explains its reduced performance compared with other treatments.

Keywords: Fat supplementation, animal performance, fatty acids