Feeding Polyunsaturated Supplements to Grazing Dairy Cows Improve the Healthy Value of Milk Fatty Acids

Abstract

The objective of the experiment was to improve the healthy value of milk fatty acids (FA) by feeding sunflower oil (SO) or sunflower seed (SS) combined or not with fish oil (FO) to grazing dairy cows. Four Holstein cows (515 ± 80 kg liveweight) in late lactation (230 days postpartum) fitted with ruminal cannulae were allotted to a 4 × 4 Latin square design with factorial arrangement of treatments: SS = 1.9 kg dry matter (DM)/cow/d of SS; SO = 0.8 kg/cow/d of SO; SS-FO = SS + 0.24 kg/cow/d FO and SO-FO = SO + 0.24 kg/FO. Cows grazed a high quality pasture offered at 11 kg DM/cow/day. After the afternoon milking cows also received 5.6 kg DM/cow of corn silage and during each milking time cracked corn grain (1.3 kg DM/cow) mixed with a mineral-vitamin premix was fed. Oils and SS were introduced via ruminal cannulae and SS was fed roughly grounded. Milk yield tended (p < 0.07) to increase in SO treatments (9.9 vs 8.7 kg/d). Yields (kg/d) of fat corrected milk (FCM) (8.01 vs 6.37) and milk fat (0.27 vs 0.191) increased (p < 0.05) in SO diets and milk fat content was not affected. Milk protein concentration (40.5 vs 37.0 g/kg) and yield (0.397 vs 0.322 kg/d) were higher (p < 0.05) in SO without effects of FO or their interaction. Milk cholesterol content did not differ. The reduction in the atherogenic saturated FA of milk averaged 63% for C12:0, 51% for C14:0 and 29% for C16:0. Atherogenicity index (AI) of milk was reduced particularly in SS-FO. Basal concentration of cis-9, trans-11 C18:2 (CLA) in milk was 1.39 g/100g FA and increased (p < 0.05) by 144% across treatments without differences between SS or SO. Feeding FO increased (p < 0.05) milk contents of CLA (2.86 to 3.92 g/100g FA) and linolenic acid. Comparing SO or SS with or without FO showed no changes for neutral detergent fiber (NDF) and crude protein (CP) degradation of pasture. Polyunsaturated fatty acid (PUFA) fed to grazing dairy cows had a marked effect on milk FA profile putatively enhancing its healthy value.