Lactation performance formation and life-long use specific of Ukrainian Black-and-White dairy breed cows in Kyiv region farms

Abstract

In recent years, the cows of Black-and-White Dairy breed display a short performance period, fertility reduction and metabolic diseases occurrence. To find methods of high performance animal’s selection the authors studied specific of cows use in ontogenesis. The studied of Black-and-White Dairy cows life-long use under conditions of Kyiv region. It was studied of milk yield age dynamics, maximal performance age, udder type and cows elimination during their use. The daily yield, its heritability (h²) and repeatability (r and r_w) were investigated of first-calving cows. It has been established that the absolute majority (96 %) of cows have bowl-shaped udder and bath-shaped udder. The cows reach maximal lactation performance during the fourth lactation, after that the milk yields decrease. The cows’ performance after the 8^th calving does not differ from first-calving cows. In 51% of animals brought into the herd the first lactation remains the highest. Most highly-productive cows are disposed after the first calving or their performance decreases significantly. The disposal of first-calving cows constitutes almost 22 %. 56 % of cows are decreases before the fourth lactation, when the peak performance is expected. The lactation duration was found to be rather stable (r_w = 0.409; P > 0.999) in ontogenesis.The highest correlation is observed between the duration from fourth to the sixth lactations. Within first lactation daily yields rises during the first and second months. In the third month they stabilized. Further, the milk yields gradually decrease. A high variability of daily yield of the cows should be noted. In every lactation month there were individual cows with the milk yield three times higher than the herd average. During the lactation the highest variability indices (Cv = 30.1-30.4 %) were observed in months one and nine-ten. It has been established that the daily yield of firstlings during the lactation have various heritability coefficients. The milk performance at the beginning and at the end of lactation is the best inherited (h² = 0.31-0.64). The results obtained confirm the possibility of animal’s selection with desirable forms of lactation curve. Theoretically it can be used for optimization of their energy balance during the transit period.