Cows evaluation and selection by milk yield evenness

The purpose of research is to develop a new method for assessing cows according to the evenness of milk yield and testing it in farm conditions. The studies were carried out on the basis of the Department of Mechanization and in the conditions of the KFH Mukhametshin Z.Z. the Sabinsky District of the Republic of Tatarstan. Approbation of the method was carried out on 10 first-calf heifers of the Holstein breed. Animals were kept under a loose housing system and robotic milking. Animal performance data was taken from the T4C herd management program. Previously, a detailed analysis of existing methods for assessing the uniformity of milk yield was carried out. Their positive and negative sides are revealed. Based on the results of the analysis, a new method for evaluating and selecting cows according to the evenness of milk yield was proposed. The method involves measuring the milk yield of each animal for certain time intervals (day, decade, month). Next are the coefficients of variation in milk yields of an individual cow and for the entire group. The ratio of the coefficient of variation of an individual to the coefficient of variation of the group is a criterion for the evenness of milk yields. If the criterion value is less than one, the animal is assigned to the desired type. Based on the results of the evaluation of 10 first-calf heifers, it was found that the coefficients of variation in milk yield range from 5.6 to 25.4 %. Animals on this basis are heterogeneous. Having the same conditions of keeping and feeding, cows react differently to them. 6 cows (60 %) were assigned to the desired type according to the evaluation criterion. These animals are characterized by greater resistance to temporary deterioration in the conditions of keeping and feeding, they lose less in milk yield, therefore, they are more preferable from an economic point of view. When forming a breeding core, farms are recommended to select cows there, including in terms of evenness of milk yield.