Relative variability of phenotypic traits and indicators of milk productivity of cows
Abstract
The research was conducted on cattle of Black-and-White breed (Holstein and Ukrainian Black-and-White dairy breed) at LLC “Veleten” Glukhiv district of Sumy region (n = 1956) and PJSC “Breeding Plant “Stepnoy” of Kamyansko-Dniprovsk district of Zaporizhzhia region (n = 1981). Based on retrospective data analysis (“Uniform-Agri” – program of dairy herd management) for the period from 2004 to 2017 it was studied the live weight of cows in growing period (newborns, 6, 12; 18 months, at first insemination and after the first calving), body measurements of heifers (height at shoulders, chest depth, chest width, chest girth behind the shoulder blades, oblique body length, width of hips, wrist girth) and traits of reproducibility (age at first insemination, age at first calving, duration of service period, insemination index, fertility index) and milk productivity of cows (milk yields for 305 days, fat and protein content in milk for the first, second and third lactation). Based on our previously obtained data by correlation analysis method it was studied the relative variability of phenotypic traits and indicators of dairy productivity of cows. It is established that the connections of live weight of cows during their rearing with traits of milk productivity were multidirectional and ranged from slightly improbable to moderately significant values. At the same time, in both farms, the most significant highly probable connection was noted between the live weight of animals at the age of 12 months and the milk yield of first-borns that indicates the possibility of selecting heifers at the specified age to provide them future high milk productivity. There was significant variability of the relationship between body measurements and the amount of milk yield of cows for the first, second and third lactation. However, cows of both farms, had direct connection, but a bit weaker in animals at PJSC “Breeding Plant “Stepnoy”. Positive correlation coefficients between indicators of exterior and milk yields of cows give reasons to claim the efficiency of indirect selection of heifers by body measurements. Rational management of dairy farming and high profits depend a lot on knowledge of regularities of correlative variability of productive traits of cows and indicators of reproductive capacity. It is established that the connections between the traits of milk productivity and reproductive capacity of animals were different and ranged from weak to medium and from reliable to improbable. The most significant highly reliable, however, with negative correlation coefficients were observed between milk yield of cows for all studied lactations and their age at the first insemination and the first calving
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