Evaluation of bulls of Mikhailovsky type on quantitative and quality indicators of milk of daughters
Evaluation of bulls on quality of offspring is the basic link in system of breeding work with herds and breeds, in creation of new types of a dairy cattle, breeding lines. The selection of two breeding lines of a horned cattle with use of bulls of Mikhailovsky type of the Yaroslavl breed of a dairy cattle now is conducted in Yaroslavl region. Under the existing instruction only milk yields and butter-fat of offspring in comparison with contemporaries is considered at an evaluation of bulls on breeding categories. However the following qualities have a great value: the protein content, technological properties, cheese making suitability, quantity of somatic cells in milk. Besides, at cross-breeding value of bulls is expedient for estimating with application of additional methods: comparison of daughters with mothers and contemporaries, calculation of heritability of signs and prepotence of bulls-fathers, degree of realisation of a parental index in offspring. Three bulls of Mikhailovsky type (with a Holstein thorough-bredness at 75,0; 76,7 and 87,5%) are estimated on dairy effi ciency of the first heifers daughters. Parental indexes of bulls on efficiency of female ancestors, their realisation in offspring which appeared various depending on paratypical factors are calculated. Hereditary conditionality of signs from mothers by a method of correlations in related pairs “mother-daughter” is revealed. The prepotence of each bull is established by the D.T. Vinnichuk’s prepotence index. By results of a complex evaluation the breeding value of bulls is defined and recommendations of improving selection by a protein content to daughters in offspring of a bull of Zevs 1155 are made.