Milk Production, Composition, and Fatty Acid Profile in Milk from Dairy Cows Fed Increasing Levels of Dietary Soybean...

The objective of this study was to evaluate the effects of dietary inclusion of increasing levels of soybean oil on milk yield, milk composition, and milk fatty acid profile in dairy cows. The experiment was designed as a 4 × 4 double Latin square with 21-day periods and used eight Holstein cows (body weight of 550 ± 19.5 kg and 200 ± 5 days in milk). The treatments evaluated were a basal diet without soybean oil and a basal diet added with 10, 20, or 30 g/kg DM of soybean oil. None of the treatments evaluated affected (p > 0.05) milk yield, dry matter intake, dry matter digestibility, or the concentration of fat, non-fat solids, protein, and lactose in milk. Furthermore, increasing levels of soybean oil included in the diets did not affect (p > 0.05) the milk concentration of butyric, caproic, caprylic, capric, lauric, pentadecanoic, palmitoleic, heptadecanoic, and linoleic fatty acids. However, dietary inclusion of soybean oil decreased (linear effect; p ≤ 0.05) the milk concentration of myristic, palmitic and oleic fatty acids. In contrast, higher concentrations (linear effect; p ≤ 0.05) of stearic fatty acids were observed in the milk of dairy cows fed soybean oil in their diet. In conclusion, dietary inclusion of increasing levels of soybean oil (30 g/kg DM) modifies the fatty acid profile of milk without affecting milk yield or the protein, fat, or lactose content.