In modern conditions of intensive dairy farming, the first and most important task was to ensure a high level of productivity of cows with simultaneous long-term use. Taking into account the important breeding aspect of the measure for intra-and interlinear breeding, it was considered appropriate to study the efficiency of combining the lines at the breeding of animals of the Sumy intra-breed type of Ukrainian Black-and-White diary breed by traits of longevity. The research on determining the effectiveness of combining the lines at breeding of cows on grounds of duration of use and lifetime productivity was carried out in the herd of pedigree plant PE "Burynske" of Pidlisnivskyi department in Sumy district.
According to the results of evaluation of cows obtained by intrabreeding selection of eight genealogical formations of the experimental herd, was found significant effect of heredity lines on indicators of longevity. According to the estimation of longevity, the offspring of four lines were the best: Valiant, Sjuprim, Starbuck and O. Aivengo. Advantage of daughter progeny of sires Valiants line with the highest longevity over the animals of lines of Montfrech, Matt, M. Chiftein and S. T. Rokita on this basis amounted to 252–526 days (P < 0.01–0.001). The next by lifetime rating was the offspring of O. Aivengo's line sires had an advantage over cows of the above lines with variability of 220–393 days (P < 0.05–0.001).
The same lines (Valianta, Sjuprim, Starbuck and Aivengo) almost did not differ among themselves by the number of used lactations (4.6–4.8) and exceeded cows of remaining lines by 0.6–1.4 lactation. The difference between the maximum and minimum values was reliable at P < 0.001.
The highest yield for a productive life was obtained from cows belonging to the Aivengo line 1189870, which with a high reliability of difference predominated the offspring of all estimated lines with variability from 3532 (P < 0.001; Syuprim line) to 13617 kg of milk (P < 0.001; line Montfrech). High lifetime milk yields differed also descendants of sires lines Sjuprim (29684 kg), Starbuck (26811 kg) and M. Chiftein (26516 kg).
Among the crossed variants with the minimum longevity indicators, offspring derived from bulls-sires of interlinear selection ♂Montfrech × ♀Mett and the reverse cross – (♂Mett × ♀Montfrech) are distinguished. This was explained to a certain extent by the fact that continuators of these lines were only crossbred sires of Ukrainian Black-and-White diary breed. In variants using the parent lines of Monfrech and Matt with maternal lines, the successors of which are Holstein sires, longevity indicators in the offspring obtained from these crosses are improving.
According to the lifetime yield of dairy fat, the highest rates were obtained from offspring with interlinear selection of those sires who have the highest lifetime yield of milk. These daughters are from the crosses ♂Starbuck × ♀Sjuprim (1197.4 kg) and ♂S. T. Rokita × ♀Aivengo (1189.6 kg).
An indicator of the effectiveness of longevity was also milk yield per day of life of dairy cows. Variability in interline selection varied from 8.7 (♂Metta × ♀Monfrech) to 12.0 kg (♂S. T. Rokita × ♀Aivengo). The difference between these variants was 3.3 kg with high reliability (P < 0.001; td = 5.95).
Conclusions. Identified and confirmed statistical significance regularities concerning to influence the level of traits duration of use and lifetime productivity of an alternative selection system of linear breeding convinced about feasibility of regular monitoring to assess the combination of lines in the further breeding selection cows of Sumy intrabreed type of Ukrainian Black-and-White dairy cattle. Re-selection of the best options and rejection of ineffective ones will help to increase the genetic potential of longevity traits.
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