The effects on milk yield and composition of incorporating lactose into the diet of dairy cows given protected fat

Twenty-eight Holstein/Friesian dairy cows were divided into four groups of seven. From weeks 4 to 15 of lactation they were given a basal diet consisting of 8 kg hay, 2 kg sugar-beet feed and 2 kg grass nuts, together with a concentrate allowance of 8 kg/day. Concentrates for group A were based on cereals and soya (control). Concentrate B contained 60 g protected fat supplement per kg; concentrate C contained 100 g lactose per kg; concentrate D contained 60 g fat supplement and 100 g lactose per kg. Milk yields were 24 . 6, 27 . 7, 25 . 6 and 26 . 5 kg/day and milk protein concentrations were 32 . 3, 30 . 7, 32 . 7 and 31 . 9 g/kg for groups A, B, C and D respectively The effect of fat supplementation on milk yield and protein concentration was significant (P < 0 . 05) but the effect of lactose was not significant. Milk fat concentration was not significantly affected by treatment. It is concluded that lactose can partially alleviate the depression in milk protein concentration often observed when cows are given protected fat.