PRODUCTIVE QUALITIES OF COWS OF DIFFERENT GENOTIPIV AND THEIR ADAPTIVE CAPACITY TO HOT WEATHER
Authors: Verbuch I. V. , Medvid O. V. 
Published: August 2022

Goal. To study the influence of breed affiliation on milk productivity, milk quality indicators and adaptability of animals of different genotypes to the action of hot weather conditions. Methods. Zootechnical, physical and biometric analyzes. Results. According to research results, the highest hopes for 305 days of three lactations are in purebred cows of Ukrainian Black-and-White dairy breed with the appropriate indicators: for the first lactation – 5029.1 kg, for the second lactation – 5268.5 kg, for the third lactation – 5386.4 kg, which is more than local cows obtained from crossing cows of Ukrainian Black-and-White dairy breed with bulls of Swiss breed, in terms of lactation, from 93.8 kg to 146.6 kg. For the above-mentioned lactations, local animals have an advantage in fat content of 0.19–0.26% and protein content by 0.14–0.19% and are superior to purebred animals in milk fat yield by 3.0–9.5 kg and protein by 2.6–6.4 kg.

One of the indicators of milk productivity in breeding work with dairy cattle is the index of constancy of lactation, which is determined as a percentage and the closer it is to 100, the more stable will be lactation. According to the index of lactation stability, local animals have a slight advantage, which is 3.6% over purebred peers, with a significant difference (td = 2.11).

Studies on the effect of elevated temperatures on the adaptability of cows of different genotypes were conducted in the period from May to September, when the temperature was 28–37 degrees Celsius. As a result of our research, we found that the change in air temperature from +18°C in the morning to +32–35°C in the afternoon (the second, third decade of July 2021) differently affected the clinical and physiological parameters in cows of different genotypes. The increase in daytime air temperature was accompanied by an increase in the number of respiratory movements in purebred and domestic animals, respectively, by 13.7 ± 0.96 (P < 0.05), and 9.9 ± 0.91, (P < 0.01) breath .movement / min. than in the morning The increase in rectal temperature in purebred and local cows occurred by 0.9 ± 0.09 (P < 0.001) and 0.5 ± 0.13°C (P < 0.001), respectively. The body of local cows was more resistant to the action of elevated ambient temperature, which was manifested in smaller fluctuations in their clinical indicators. At the same time, purebred animals outnumbered local cows by 7.3 breaths / min, respectively, in terms of the increase in the number of respiratory movements and the increase in body temperature. (P < 0.001) and 0.30°C (P < 0.01). The research results show that the coefficient of thermal vulnerability (according to AF Dmitriev) in domestic cows is lower than in purebred animals by 0.12 (P < 0.01). The heat resistance index in domestic cows was higher than in purebred animals by 8.1 (P < 0.01).

We also studied the adaptive abilities of animals to environmental conditions in different periods. For this purpose, during periods of temperature stress (28–37°С), general clinical indicators were determined: internal body temperature and respiratory rate. Based on these data, we calculated the coefficient of thermal sensitivity of cows according to the formula M. V. Benezra (1954). The obtained data show that in all studied periods purebred animals are characterized by greater thermal sensitivity than domestic animals.It should be noted that the most sensitive animals of different genotypes were exposed to hot weather conditions at a temperature of 32–37°C. The coefficient of thermal sensitivity in different study periods in domestic cows was lower compared to purebred animals by 0.11–0.39 (P < 0.001).

According to the results of the research, the dependence of heat resistance of cows on their genotype was established. Local cows have the best adaptive abilities to hot weather conditions, as they have more balanced heat resistance. Conclusions. Comparative analysis of milk productivity shows that the highest hopes for 305 days of the three considered lactations are in purebred cows, which are dominated by local cows, in terms of lactation, from 93.8 to 146.6 kg of milk. At the same time, for the above-mentioned lactations, local animals have an advantage in terms of fat content by 0.19–0.26%, and protein content by 0.14–0.19%, and in terms of milk fat yield, respectively, by 3.0–9.5 kg and protein by 2.6–6.4 kg. At the same time, higher adaptive abilities of local cows to the action of hot weather conditions have been established, as they have more balanced indicators of heat resistance.