CORRELATED VARIABILITY OF DOMESTIC AND FOREIGN ASSESSMENT OF THE BREEDING VALUE OF BULLS

The purpose of the research was to determine the repeatability of estimates of the breeding value of bulls by offspring in foreign countries and in controlled herds in Ukraine. The study was conducted based on the results of native (by the method of calculated breeding value – CBV, n = 1093) and foreign (the best linear unbiased prediction – BLUP, n = 161) assessment of the breeding value of sires with a repeatability of more than 60% of ten dairy and double breeds, given in the catalogues of bulls for the reproduction of breeding cattle in 2003–2013. By breed affiliation, these 713 bulls are classified as Holstein, 92 – Ukrainian Black-and-White Dairy, 85 – Ukrainian Red- and-White Dairy, 59 – Ukrainian Red Dairy, 47 – Simmental, 40 – Angler, 36 – Swiss, 11 – Red Steppe, 7 – Red Danish, 3 – Lebedyn breeds. By country of birth (selection), the largest representation (439 bulls) had sires of native breeding, 235 bulls used in the specified period (or their sperm products) were imported from Canada, 154 – from Germany, 117 – from the USA, 37 – from Austria, 36 – from the Russian Federation, 20 – from Denmark, 19 – from Hungary, 17 – from the Netherlands, 7 – from Great Britain, 4 – from the Czech Republic, by 2 – from France, Latvia and Estonia and by one from Bulgaria and Lithuania. On each sire the information about the year and the method of evaluation by offspring, the number of daughters, herds and repeatability, average milk yield, the content and yield of milk fat and protein in daughter’s milk, the breeding value of bulls on these traits was taken into account. Prior to receiving an estimate for offspring in Ukraine, 161 sires were evaluated abroad. 
Correlation analysis established a statistically significant (P < 0.001), but relatively low (27.8–51.7%) level of correlated variability of the breeding value of bulls and the average productivity of their daughters. On the yield, the correlation coefficient was 44.5 ± 2.71%, on the fat content – 51.7 ± 2.59%, protein content – 27.8 ± 3.30% and milk fat yield – 42.8 ± 2.74%. Consequently, the average milk production of daughters cannot be considered as a reliable criterion for assessing the genetic value of sires. 
The breeding value of sires by the milk yield of daughters closely correlates with that of milk fat and protein (97.3...97.9%) and reveals a low connection (-2.7...-7.8%) with their content, which confirms the natural antagonism of quantitative and qualitative traits of milk production. Consequently, selection on the basis of milk production should be carried out at independent levels with a low probability of obtaining bulls, which simultaneously improve quantitative and qualitative traits. 
Correlation analysis revealed a low and in most cases not reliable level of correlated variability of native and foreign estimates of the breeding value of bulls. On the yield, the repeatability of foreign and native assessment of the breeding value of sires was 33.6 ± 7.29% (P ˂ 0.001), by fat content – 13.0 ± 7.67% (P = 0.093), by milk fat yield – 8.6 ± 7.71%, by protein content – -0.1 ± 7.83% (P = 0.991), milk protein yield – 23.7 ± 7.61% (P = 0.002) and by the complex breeding index – 13.8 ± 7.66% (P = 0.074). Thus, the level of breeding value of sires determined abroad can be considered only as a preliminary one for their selection into native herds, which does not guarantee the corresponding breeding effect due to the different reaction rate in the interaction "genotype – environment". Quite reasonable so is the requirement of the native instruction on the selection of bulls concerning the mandatory reevaluation of imported bulls as well as sires, whose sperm products were purchased by import into Ukraine.