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Lobachova IV. Correlation of reproduction rates of Ascanian Merino ewes with air temperature and humidity. Bìol Tvarin. 2025; 27 (2): 7–13. DOI: 10.15407/animbiol27.02.007.
https://doi.org/10.15407/animbiol27.02.007
Received 17.12.2024 ▪ Revision 27.05.2025 ▪ Accepted 03.06.2025 ▪ Published online 10.06.2025

Correlation of reproduction rates of Ascanian Merino ewes with air temperature and humidity

I. V. Lobachova
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The M. F. Ivanov’s Institute of Animal Husbandry in Steppe Regions «Askania-Nova» — National Scientific Selection-Genetic Center of Sheep Breeding, 1 Soborna Str., Askania-Nova, Kakhovskyy district, Kherson region, 75230, Ukraine

Sheep are animals whose reproduction is affected by environmental conditions, and knowledge of the dependence of reproduction on climatic parameters will help to adjust the conditions of animal keeping. The purpose of the research was to investigate a correlation between the reproduction rates of Ascanian Merino ewes with such climatic factors as air temperature and humidity and the THI (temperature-humidity index). 3070 data of adult and 1.5-year-old ewes obtained during 2011–2022 were analysed. Methods of variational statistics and correlation analysis were applied. The degree of correlation was determined by the z-value (adjusted r-coefficient). The results showed that the fertility F% and fecundity Fm% had a strong negative correlation with the average daily air temperature in June — z = −0.996 (P<0.05) and −0.951 (P<0.05) respectively and a moderate one with the temperature in June–July −0.776 (P>0.05) and −0.887 (P<0.05), and the prolificacy Pf had a moderate negative correlation with the average daily air temperature in July −0.633 (P>0.05) and a strong one with the temperature in July–August −0.887 (P<0.05). The indices of the sexual activity renewal — index of heat IH_i, index of heat time IHT_i and index of conception time ICT_i — revealed a significant relationship at the level of a moderate–strong with the average daily air temperature in June 0.929 (P<0.05), 0.741 (P>0.05), 0.829 (P<0.05), respectively, which indicates a decrease in the proportion of animals with the manifestation of sexual heat and a delay of the time of the manifestation of first sexual heat and conception with an increase in the temperature in June. The dependence of reproduction rates and indices of renewal on air humidity did not exceed the level of moderate, and the relationship with the THI mainly repeated the nature of the correlation with temperature. It was concluded that the reproduction rates of ewes of the Ascanian Merino breed at a moderate–strong level correlate with the temperature factors. Indicators related to the manifestation and time of heat show a greater level of correlation with the temperature in June, prolificacy — with the July parameter.

Key words: sheep, heat, sexual activity, climatic factors, correlation

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