Age at first conception of high yielding cows

Black and White low land dairy cattle have very pronounced ability for high production of milk. Fertility is the major trait of cattle and key factor in successful milk production. Fertility traits have pronounced variability and low heritability value. Fertility is regularly limiting factor in attempts to increase the milk yield. Age of dairy cattle at first conception is one of the major reproduction properties. Age of calves at first calving depends mainly on age at first conception. Previous researches have indicated what would be the optimum age at first conception of Black and White heifers. Age at first conception is determined by the date of birth and date of first conception. Knowledge of the strength of the environment factors on age at first conception in high yielding cows is important from the aspect of their inclusion into the model. According to the significance of individual systematic factors, their objective assessment was carried out for the purpose of accurate evaluation of obtained results. Objective of this paper is to study the age at first conception of high yielding Black and white cows through major systematic influences, by applying adequate methodology. Cows comprising the studied sample (n=331) belong to European type of Black and White dairy cattle in final stage of improving of this breed with Holstein-Friesian breed. Average age of dairy cattle at first conception was 491.19?9.36 days or 16.15?0.31 months. According to cows? the values were following: 479.31 days (> 73% HF), 486.12 days (58-73%HF) and 508.14 days (< 58% HF).