THE RELATIONSHEEP OF THE BREEDING VALUE OF BULLS WITH THE PRODUCTIVITY OF THEIR MOTHERS AND THE BREEDING VALUE OF THEIR PARENTS BREEDING
Authors: Kulakova M. B. , Polupan Yu. P. 
Published: January 2022

Having a correlation between the pedigree value of the parents and the productivity of the mothers with the pedigree value of the offspring (inheritance through "father-son" and "mother-son") would increase the likelihood of selecting breeders at the stage of custom mating to obtain repair bulls.

According to the contradictory results of research by various authors, the tendency is low to directly link the breeding value of bulls in milk productivity of daughters with milk yield and milk fat of mothers and slightly higher – with the breeding value of their parents. At the same time, the degree of straightness or curvature of such relative variability remains little studied, which became the goal of our research.

The research was conducted based on the results of the evaluation of dairy and dairy-meat bulls used in domestic herds during 1997–2004. The analysis included information on the breeding value of 293 bulls, estimated by the method of estimated breeding value UA (EBV), and the parents of bulls – the estimated breeding value (EBV) method or the method of best unbiased linear forecast (BLUP) in foreign countries (ETA, FW, ICC, PTA, ZW , EBV, BV, GB). These broods were estimated at an average of 54 daughters in 4.4 herds with an average recurrence rate of 64%. The average milk productivity of bull daughters for 305 days of the first lactation was 5471 kg of milk with 3.79% fat and 3.29% protein, daughters of bull parents – 7099 kg, 3.78% and 3.21%, respectively. In the mothers of bulls, productivity was taken into account for the highest and the average was calculated for all taken into account lactations. According to the vast majority of the considered features, the asymmetry index did not exceed 1, and the excess – 3 units, which indicates a close to normal distribution and legitimacy of the use of parametric statistics. The predominant assessment of breeders for a small number of daughters and a small number of herds logically determined a statistically significant level of positive asymmetry (2.99 ± 0.142 and 2.79 ± 0.142, respectively) and excess (12.21 ± 0.284 and 11.48 ± 0.284) for these parameters.

The direction of relative variability and the degree of its straightness or curvature was assessed by the comparison of group means. According to each of the determinants of the parents, five groups of offspring were formed. According to the mother's milk yield, the class interval for the highest lactation is 1500 kg, according to the average mother's milk yield – 1000 kg, according to the father's selection index – 300 units and according to the father's breeding value – 400 kg. The parameters of the variation series were calculated by the methods of mathematical statistics and biometrics using the software package Statistica 12.0.

Comparative analysis revealed a significant level of intergroup differentiation of milk productivity of daughters and breeding value of bulls with different milk yields of their mothers for higher lactation.

With the increase in the milk yield of mothers of bulls from less than 7.5 to more than 12 tons, hopes, the yield of milk fat and protein in the daughters of the firstborn are steadily increasing. The growth of breeding value of offspring with increasing milk yield of their mothers for better lactation is crooked. In particular, in the group with milking of mothers 10501–12000 kg the pedigree value of broodstock on milking of daughters decreased in comparison with the previous adjacent class (9001–10500 kg) by 110.3 ± 88.98 kg, on milk yield – by 5.0 ± 3.44 kg, milk protein – by 4.8 ± 4.72 kg. There is almost no intergroup difference in breeding value in terms of fat and protein content in daughters' milk.

Another component of the selection of repair bulls by origin is the breeding value of their parents. Comparative intergroup analysis shows a curvilinear increase in milk yield, milk fat and protein yield of first-born daughters and breeding value of bulls on these grounds with increasing the complex selection index of their parents.

In the first two adjacent classes there is even a slight decrease in the productivity of daughters and the breeding value of breeders. Increasing the breeding value of sons begins only in groups from the parents of improvers. The maximum value of the difference in milk productivity of daughters was observed between groups of parents with a selection index of more than +700 and within -200… + 100 units.

A comparative analysis of groups on the pedigree value of the father of a bull by milking also found that the increase in the breeding value of parents is accompanied by a curvilinear increase in the breeding value of sons and the average milk yield of their daughters. According to the average breeding value of bulls in terms of milk fat and protein content, the intergroup difference does not show a clear pattern with the breeding value of the father in terms of milk yield, is multidirectional and in most cases does not reach a statistically significant level.

A certain level of relative variability has been established between the milk productivity of mothers above and above all lactations, the breeding value of fathers and the breeding value of sons and the milk productivity of their daughters. With the increase in the productivity of mothers and the breeding value of fathers, the breeding value of the bulls of sons and hopes, the yield of milk fat and protein in the milk of daughters increases curvilinearly. Increased productivity of daughters' cows and breeding value of breeders are more likely to be provided by the high level of productivity of their mothers and breeding value of parents. Taking into account the milk productivity of mothers for all lactations in the selection of broodstock does not provide a significant increase in the probability of obtaining improvers compared to taking into account the milk yield of mothers for higher lactation.