Effective interbreed selection, which involves family breeding, is an important task today, because the presence of valuable families characterizes the degree of herd selectivity and the level of breeding in it. Therefore, the purpose of our research was to conduct a retrospective analysis of the zootechnical accounting data of dairy productivity and breeding value of cow families at highly productive herd of Public joint-stock company “Stud farm “Stepnoy”, in Kamyansko-Dniprovskyy district of Zaporizhzhya region created by crossbreeding of the females of the Ukrainian Black-and-White dairy breed with Holstein breeders. The analysis included 45 families, with a head count of 8 to 19 heads, including foundation cows. Malta family UA2300205993 had the maximum number of descendants (6 daughters, 6 granddaughters and 6 great-grandchildren), and Malta family UA2300241359 (3 daughters and 3 granddaughters) – minimal. Found to be that the families under control were characterized by a significant level of differentiation in milk yield and fat and protein content in milk. The Mazi family UA230023375 was the best by milk yield, the Lemonka family UA2300233684 – by the fat in milk, by the protein in milk – Nasypa UA2300222571. At the same time, foundation cow Kviten UA2300077306, Nasypa UA2300222571, Yana UA2300248883, Lamysta UA2300198909 and Sokyra UA2300241365 had the most highly productive daughters; their milk yields for higher lactation was in the range 11143.5–12780.0 kg. At the same time high-productive foundation cows did not always receive high-productive daughters. In particular, 3 daughters of the foundation cow Krovlya UA2300229133, whose milk yields for higher lactation was 12671 kg, had lower milk yields by an average of 2704.7 kg. However, foundation cows with low milk yields level had daughters who had this rate significantly higher, including the foundation cow Kviten UA2300077306, Toskana UA2300077167, Liga UA2300034958, Maket UA2300241388 and Manilka UA2300233701, whose highest milk yields level for the highest lactation was in the range 5625–7701 kg, and ho had daughters whose milk yield was higher than their mothers by an average of 4858.5; 3975.3; 3704; 3299.5 and 3186.7 kg respectively.
The granddaughter of the experimental foundation cows ranged from 8413.0 to12942.6 kg, fat content in milk – from 3.50 to 4.13% and protein content in milk – from 3.05 to 3.29%, and the figures of great-grandchildren were respectively 7114.0–11991.3 kg, 3.49–3.92% and 3.00–3.29%. It should be noted that 15 foundation cows gave granddaughters with an average milk yield of over 10000 kg, 13 with a milk yield more than 11000 and 3 – with a yield of more than 12000 and only 2 foundation cows had second generation descendants with an average yield of less than 9000 kg. The grandchildren of 14 foundation cows had over 10000 kg of milk yields, and 7 over 11000 kg.
The breeding value of the foundation cows by the milk yields was within -497 (Liga UA2300034958) – +1614.4 kg (Tsykl UA2300233484), by the fat content in milk – within -0.098 (Hanh UA2300233710) – +0.280% (Stezhka UA2300205863) and by the protein content of milk within -0.073 (Maket UA2300241388) – +0.053% (Stezhka UA2300205863), breeding value by the above indicators of their daughters were accordingly within -554.9 – +819.3 kg, -0.065 – +0.095% and -0.038 – +0.045%, granddaughters – within -326.3 – +786.2 kg, -0.048 – +0.145% and -0.033 – +0.025% and to a great-granddaughters – within -670.5 – +590.3 kg, -0.067 – +0.043 and -0.043 – +0.030%.
The most valuable in the herd relation by milk yield appeared to be Mazi family UA2300233755, Lemonka family UA2300233684 – by the fat content in milk and by the protein content in milk – the Nasypa family UA230022257. Among evaluated families by the nature of changes in breeding values in generations 31 (68.9%) were progressive, 4 (8.9%) were stable and 10 (22.2%) regressive. The prediction of the efficiency of dairy cattle breeding and prediction of certain changes by the productivity indices of subsequent generations can be made by correlation and regression coefficients of the main features: milk yield, fat content, and protein content in milk. The highest and most likely coefficients of correlation (r = 0.39) and regressions (R = 0.42) were observed between the milk yield of foundation cows families and their daughters. Each succeeding generation had declined and the indices of descendants of the third generation were unreliable.
Influence of foundation cows in future generations, depending on the generation and nature of the features of milk productivity, was also different. Milk yield (h2 = 0.26–0.79) was characterized by the highest and most reliable heritability estimate, much lower and unreliable in the second and third generations – the fat (h2 = 0.10–0.22) and protein content in milk (h2 = 0.12–0.24). It indicates that in the controlled herd more attention is paid to milk yield focus breeding. Therefore, to improve family fat and protein content in milk it should be used breeders whose mothers have high fat and protein content in milk.
Correlation between the breeding indicators of black and white cows in Bulgaria