Abstract
Age and live weight at the first fruitful insemination of replacement heifers is an important link in the breeding process. A study was made of the influence of several factors on the productive longevity of cows of the Holstein-Friesian breed. The relationship between lifelong milk yield and longevity with the age of the first fruitful insemination is higher (r = 0.10-0.23) than with the live weight at the first insemination (r = 0.04-0.13). The breed of animals does not affect the degree of relationship between age and body weight at the first fruitful insemination and their productive longevity. Increased indicators of productive longevity are characteristic of animals of Gilan Dairy Farms and ASA Animal Husbandry, inseminated at an earlier date of 14-16 months. with increased live weight. Analysis of the results obtained allows us to conclude that the factor ‘farming’ in the dispersion complex had a slight effect on the indicators of productive longevity of cows.
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