The impact of environmental temperature on ewe reproduction, adaptive responses during insemination, and productive characteristics of the lambs obtained from them

Abstract

The reproductive function of ewes and the development of their offspring are largely influenced by their clinical condition and the temperature of the environment. The maximum temperature values have significantly increased over the last two decades, making climate change a pressing issue for sheep breeding worldwide, including Ukraine. The consequences of exposure to high temperatures of the outside air, above all, in the mating season, can be marked by a significant increase in the heat load on the body of the brood stock, a decrease in clinical indicators and reproductive capacity. On the other hand, the current understanding of how these components interact is insufficient, which conditions the relevance of this work. In order to determine the effective terms of insemination of sheep in the mating season of 2021, taking into account the terms of insemination and the characteristics of the outside air temperature, three technological groups of ewes were formed, which were in the same flock and were artificially inseminated with freshly obtained sperm from the same breeders in August–September: from August 15 to August 27; from August 28 to September 9 and from September 10 to September 21. It was discovered that ewes inseminated between August 28th and September 9th were less adaptable to environmental conditions, experiencing increased daily fluctuations of body temperature, pulse and breathing rates, stillborn lambs, cases of abortion, and decreased preservation of young animals, including ewe lambs, which are highly valuable in breeding – by 15.8% and 10.9% concerning the initial and final phases of the insemination period. However, the young lambs born from ewes inseminated between August 15th and August 27th had the highest survival rate until weaning due to better survival of ewe lambs compared to those inseminated during later phases of the mating season against the background of a lower percentage of output of rams until the moment of weaning against ewes that were inseminated from August 28 to September 9. It has been shown that the growth rate of lambs during early postnatal development varies depending on the timing of their mothers' insemination. Ewes inseminated between August 15th and 27th produced lambs with the highest weight at 90 days, reaching 26.81 and 24.18 kg, respectively; 20.1% and 26.8% more than rams, and 19.1% and 18.8% more than female lambs whose mothers were inseminated in the middle and at the end of the breeding season. A similar picture is characteristic of the average daily growth values. It was determined that the formation of clinical indicators, and above all, the body temperature of young animals born from mothers fertilized at the beginning and in the middle of the mating season, was the most intense. The results of this study made it possible to understand the adaptive mechanisms of the response of sheep to changes in environmental temperature, which will be useful in future investigations to determine its effect on the thermopotential and clinical condition of lambs during the first day after birth, which is the most critical.