The influence of paratypical factors on the character of the lactation curve of Simmental ? Holstein cows

The nature of the lactation curve and milk productivity have been studied in hybrid “Simmental ? red-and-white Holstein” cows with the genotype 1/4   of Simmental breed +3/4 red-and-white Holstein breed and 1/8+7/8 of the same pedigree. The experiment was carried out at Agrosoyuz LLC in Ruzaevka district of Mordovia Republic. According to the study, cows with the 1/8 Simmental +7/8 red-and-white Holstein genotype of autumn-winter calving had the highest milk productivity. Their milk yield amounted to 8224 kg. The milk yield of cows with the 1/4 Simmental + 3/4 red-and-white Holstein genotype was 6901 kg. The coefficient of lactation constancy (CLC) in cows of autumn-winter calving was 96.0 and 97.9%. Next in terms of productivity are winter calving cows, whose milk yield amounted to 6800-8031 kg, with CLC of 94.9 - 97.8%. The lowest productivity was obtained from cows of summer calving period. The LP increases from 88.7 to 97.0% with the increase in cows live weight at first calving in the group of animals with the 1/4 Simmenta l +3/4 red-and-white Holstein genotype. In animals with the 1/8 Simmental +7/8 red-and-white Holstein genotype, the CLC increases from 97.6 to 98.1%. Based on the research conducted, we can conclude that the live weight of first-calf cows should be 580-600 kg. Under these conditions, high milk productivity is very likely. Analysis of the degree of influence of the service period value on the CLC showed the following: this indicator increased by 6.0% in 3/4 Holstein-bred genotype animals with the extension of the service period from 110.7 to 169.9 days; the increase of this indicator was only 1.1% in cows with 7/8 red-and-white Holstein genotype with a service period of 116.0-173.3 days. In highly productive cows, regardless of genotype, an increase in milk yield is associated with higher CLC.