[The influence of method of milkability control of] Simmental breed cows on additive components of the variance of bulls-fathers
2006
Djurdjevic, R., Stocarsko veterinarski centar za reprodukciju i vestacko osemenjavanje Velika Plana, Velika Plana (Serbia) | Bogdanovic, V., Poljoprivredni fakultet, Beograd - Zemun (Serbia) | Antov, G., Poljoprivredni fakultet, Novi Sad (Serbia)
By using two methods of calculating milkability for 300 days, the phenotypical and genetic parameters for amount of milk during lactation were appraise. The first method was classical A method, and the second the Test Interval Method by ICAR. Research includes the first lactation (n=636) which is controlled in interval of 26 and 33 days. For appraise of phenotypical and genetic parameters we use the method of the smallest squares-mixed model. By analysing the components of the variances of fathers and the use of intra-class correlation between the groups of step-sisters, who have same father-bull, we appraise the heritability for the amount of milk given by their daughters. The conslusion is that phenotypical differences between methods are significant. Fixed influence of farm, year and season of calving on amount of milk by control periods are important, too. Heritability varies between methods during lactation and althou in one particular method, between 0.054 and 0.32 for the fifth and the tenth control period in classical A method, and between 0.106 and 0.311 for the first and the tenth control period in Test Interval Method. The importance of systematic factors is the reason for using mixed model of appraising genetic parameters because it enables more objective appraise. Following the appraise of heredity during lactation helps in choosing method for selection of cattles in order to get faster informations about additive genetic value of individual candidate for selection.
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