LACTATION PERFORMANCE OF HIGH-YIELD FIRST-CALF COWS

Abstract

The results are given from the studies on lactation performance of fi rst-calf cows belonging to different sire lines. The research was conducted in 2017 in Novosibirsk region into 42 fi rst-calf cows of black-andwhite Holstein breed, belonging to the sire lines of Wis Ideal and Refl ection Sovereign, during 150 days of lactation. The pipe-line milking of cows was performed by DeLaval milking machines with adjustable pumping. Monitoring of lactation performance, intensity of milk fl ow, content of fat and protein was carried out monthly. The largest daily milk yield of cows of both lines was noted in the second month of lactation. In the fourth and fi fth months of lactation an average daily milk yield of cows belonging to the Refl ection Sovereign line was higher than that of cows of Wis Ideal line. However, in general, there were no signifi cant differences in lactation performance of cows of these lines. In the second and third months of lactation, cows of both lines had a decrease in the content of fat, protein and intensity of milk fl ow with a gradual increase in these indices in the fourth and fi fth months of lactation. First-calf cows with an average daily yield of 22.9 kg of milk had a higher content of fat and protein (by 0.98 and 0.40% respectively) than cows with an average milk yield of 36.6 kg. It was also noted that with the increase in the level of milk yield there was a tendency for the decrease in the latent period of milk ejection refl ex.