0758 Effects of feeding different forms of polyunsaturated fatty acids on performance, plasma metabolites, and milk fatty acid composition of dairy cows

Objectives were to determine the effects of feeding different types of PUFA on performance and yield of fatty acids in Holstein cows. Eight ruminally cannulated primiparous cows were randomly assigned to a replicated 4 × 4 Latin square design (28 d; 19 d adaptation, 7 d collection, and 2 d rumen evacuation). Diets were identical except for the type of fatty acid supplements that were incorporated at 2.1% of dietary DM. Supplements were Ca salts (CaS) of palm oil (CaSP), oil (O; a blend of 45% palm and 55% soybean oils), CaS of O in a granular form (CaSOG), and CaS of O in a pelleted form (CaSOP). Intake and yield and composition of milk were averaged from d 20 to 26. The fatty acid profile of milk fat was analyzed in samples collected from d 24 to 26. Blood was sampled at 0, 3, 6, 9, and 12 h relative to feeding on d 26 and analyzed for hormones and metabolites. Ruminal pH was measured for 72 h in each period. Data were analyzed by ANOVA with the MIXED procedure of SAS for a replicated 4 × 4 Latin square. Results of cow performance are presented in Table 1. Results in the text are presented in the following sequence: CaSP, O, CaSOG, and CaSOP. Feeding O increased (P ≤ 0.05) rumen fluid pH compared with CaSP or CaSOG (6.22, 6.31, 6.20, and 6.26 ± 0.07). Plasma concentration of glucose increased (P ≤ 0.05) in O compared with CaSP and CaSOG and tended (P = 0.08) to be greater than CaSOP (64.8, 66.3, 64.7, and 64.9 ± 0.55 mg/dL). Glucagon concentration in plasma tended (P = 0.06) to be greater in CaSP compared with CaSOP (156.4, 152.6, 149.4, and 144.8 ± 8.0 pg/mL). There were no treatment effects on plasma insulin, NEFA, and urea N concentrations. Milk linoleic (3.29, 3.22, 4.88, and 4.71 ± 0.16 g/100 g of fatty acid) and linolenic acids (0.43, 0.46, 0.61, and 0.53 ± 0.02) and total n-3 (0.46, 0.48, 0.64, and 0.56 ± 0.02) and n-6 fatty acid yields (3.78, 3.64, 5.37, and 5.19 ± 0.17) increased (P < 0.01) in cows fed CaSOG and CaSOP compared with cows fed CaSP or O. Conjugated linoleic acids trans-10 cis-12 and trans-9 cis-11 were reduced (P < 0.01) in cows fed CaSP compared with cows fed other treatments (0.004, 0.013, 0.019, and 0.019 ± 0.003). Source of fatty acids did not affect DMI or milk yield, but feeding O as CaS in a pelleted form improved milk fat content. Feeding CaS of O either as granular or pelleted increased content of PUFA in milk fat.