Milk yield, milk composition, fatty acid profile and indices of milk fat quality as affected by feeding with extruded full-fat soybean

Abstract

The aim of the study was to evaluate the effect of extruded full-fat soybean in diets of dairy cows on nutrient intake, milk yield, content and daily production of milk components, fatty acid (FA) profile and indices of milk fat quality. Four lactating Holstein cows were divided into control group fed a diet containing extruded rapeseed cake (R) and the experimental group fed a diet in which a part of extruded rapeseed cake was substituted by extruded full-fat soybean (RS). Dry matter intake (DMI), milk yield and milk composition were recorded. Milk FA profile was determined with subsequent calculation of atherogenicity index (AI), peroxidisability index (PI), desaturation indeks (DI) and spreadability index (SI) characterising quality of milk fat. Cows fed diet containing RS had higher DMI (17.8 kg/d) than cows fed diet containing R (16.8 kg/d, P<0.05). Milk yield in RS (19.5 kg/d) was higher compared to R (17.6 kg/d, P<0.05). Content of protein and casein was lower in RS than in R while content of lactose and urea was higher in RS than in R (P<0.05). Experimental diet (RS) compared to control (R) had higher (P<0.05) content of unsaturated FA (31.64 % and 30.69 %, respectively). Content of polyunsaturated FA in RS (4.03 %) was significantly higher (P<0.05) than in R (3.66 %) mainly due to differences in C 18:2n6c, C 18:3n6 and C 18:3n3 FA (P<0.05). Proportion of short-, medium- and long-chain FA was similar in both groups (P>0.05). PI was higher (P<0.05) in RS than in R being 5.54 and 5.06, respectively.