Genetic parameters (heritability coefficients and genetic correlations) of the type of calving, number of stillbirths and birth weight have been evaluated in the population of Holstein Friesian cattle breed. Data sets have been analysed by means of the Mixed Least Square Model (LSMLMW). Besides a random effect of bull-sires, the model has also included the fixed effects of farm, season, sex, the evaluation of viability of calves and types of birth. Estimated heritability values and heritability errors for the type of calving (TC), number of stillbirths (SB) and birth weight (BWT) were low: 0.190 ± 0.062; 0.018 ± 0.006 and 0.149 ± 0.051, respectively. Heritabilities of the analysed traits were evaluated on the grounds of the calves` bull-sires additive value (direct heritability). The values of the genetic correlation coefficients between examined traits ranged from - 0.251 (correlation between the type of calving and number of stillbirths) to 0.340 (correlation between the number of stillbirths and birth weight). [Projekat Ministarstva nauke Republike Srbije, br. TR 31086 i br. TR 46006
In this study a relationship between the milk yield and following reproduction traits: number of inseminations per conception [AIS], service period [SP], age at calving [AC], calving interval [CI] and birth weight [BW] is studied. The research involved dairy cows of European type of Black and White cattle which are being intensively improved by the genes of Holstein -Friesian breed. Mean values of general average for number of inseminations per conception, service period, age at calving, calving interval and birth weight are: 2.00; 98.78; 1088.08; 376.70 and 36.40, respectively. In general, the estimated phenotypic correlations (r p ) between the milk yield over standard lactations and fertility traits were positive and unfavorable, and ranged from 0.24 for the relationship between milk yield and birth weight to 0.70 for relationship between milk yield and age at calving.
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