Abstract
Improvement of the genetic potential in terms of cows’ productivity and creation of high milk-yield cattle with good health and long productive lifetime characteristics is impossible without systematic evaluation of such traits as milk-yield, exterior, and constitution type. The aim of our research was to study the trends in exterior traits genetic selection parameters changing, determine the extent of interconnection between cow productivity traits and constitution type among the Black-Motley and Kholmogory cow breeds of the Udmurt Republic. The research based on cow breeding-stocks was carried out in 2018–2020. The sampled population included 449 specimens. The whole cow population to be analyzed was divided in 3 groups by the productivity level: 1 – low (up to 6,000 kg); 2 – moderate (from 6,000 to 8,000 kg); 3 – high (over 8,000 kg). High milk-yield cows were higher – withers height was higher by 1.5% and 1.4% (P < 0.05) – and had more elongated body (by 1.0% and 0.8%) as compared with the 1st and 2nd group specimens. Low milk-yield cows (up to 6,000 kg) had short stature and big-boned constitution type with better-developed skeleton. They had greater values of such parameters as the chest width (by 1.6%), wide hip width (by 7.3%, P < 0.01), width of loin (by 13.2%, P < 0.01), and metacarpus girth (by 3.2%, P < 0.05). Cows with a productivity level over 8,000 kg of milk per 305 days of lactation had relatively high value of the Pelvic arch length (by 2.0% and 2.3%, Р < 0.05) and the depth of loin (by 1.3% and 1.5%) with insignificant difference in rump bone length. The lowest value of the mean exterior index of constitution type (by 3.0%, P < 0.05) was observed in high milkyield cows that is the evidence of the constitution proportionality, namely, optimal relation between the body volume and the height of a cow. Moreover, the Pelvic arch index – the ratio of the Pelvic arch volume to the body length – also testifies to harmonious constitution. High milk-yield cows demonstrated this index to be the lowest (by 3.8%, Р < 0.01) and featured more harmonious constitution.
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