Effect of type of roughage on chemical composition and technological value of milk from cows fed TMR diets

An experiment was conducted to determine the degree to which feeding Polish Black-and-White Holstein-Friesian cows with total mixed rations (TMR) differing in the type of “energy” roughages (whole-crop maize silage, MS; winter barley silage, BS) and their proportion (70% or 50% in DM) relative to wilted meadow grass silage (GS) will affect the yield, chemical composition, fatty acid profile and technological suitability of milk, the quality traits and organoleptic score of some milk products (curd cheese, soft rennet cheese, creamery butter), and the fatty acid profile of butter fat. The study was carried out during the second trimester of lactation using 36 cows assigned to four analogous groups with 9 animals per group. It was found that replacing maize silage with barley silage in TMR diets had no significant effect on the yield, chemical composition, fatty acid content and technological suitability of milk, or on the content of major protein fractions and protein substances. Curd cheese and rennet cheese from the milk of cows fed diets with barley and wilted grass silages (groups BS/GS-I and BS/GS-II) and creamery butter from the milk of cows fed diets with a lower (50% DM) proportion of “energy” silages (MS/GS-II and BS/GS-II) were characterized by a higher (P≤0.01) content of solids and fat compared to analogous products from the milk of cows in the other groups (MS/GS-I and BS/GS-I). Butter from the milk of MS/GS-I and MS/GSII cows had a significantly higher content of PUFA (including C18:2 n-6, C18:3 n-6, C18:3 n-3 and CLA), and a lower content of SFA (from C-4 to C-16) compared to BS/GS-I and BS/GS-II cows. Regardless of the type of total mixed ration fed in the second trimester of lactation, the milk and milk products had desirable functional and technological properties.