Effect of extruded and roasted soybeans on lactation performance and milk fatty acid profile of early lactating dairy cows

Thirty multiparous Holstein cows (29.80 ± 4.01day in milk; 671.6 ± 31.47 kg of body weight) randomly designed to one of the control (no fat) or 4 diets with either raw soybean, extruded soybeans, roasted soybeans, or tallow, added to provide 1.93% supplemental fat for 8 weeks. Cows fed fat diets had significantly (P<0.01) high NEL intakes and FCM production (P<0.01) when compared to control with no fat. Milk fat yield and percentage of cows fed fat-supplemented diets were significantly (P<0.01 and P<0.02 respectively) higher than control. There was no significant effect of supplemental fat on the milk protein and lactose content and yield. Total saturated fatty acids percentage in milk fat was significantly (P = 0.01) decreased by fat supplementation. Full fat soybeans significantly (P<0.01) decreased concentration of short- to medium- chain (C6:0 to C16:0) saturated fatty acids compared with control, with an outstanding value for extruded soybean. A tendency for lower C6:0 and C16:0 and higher C18:0 contents in the milk of cows fed the supplemental fat was detected (P = 0.14, P = 0.16 and P = 0.11 respectively). Mono unsaturated fatty acid, total C18:1 and trans-11 C18:1 proportion was significantly (P<0.01) increased by supplemental fat. The concentration of milk fat cis-9 trans-11 C18:2 were also increased by all fat sources, but it was only significant for extruded soybeans. There were no significant differences between extruded and roasted soybeans oil in lactation performance and energy balance of dairy cows, as well as milk fatty acid profile however, cows fed roasted soybean had numerically greater FCM production and fat content and yield than cows fed extruded soybeans, and milk fat of cows fed extruded had numerically higher cis-9 trans-11 C18:2 content when compared milk fat of cows fed roasted soybeans (respectively P=0.19, P=0.054).