Influence of climatic elements on the reproductive traits of Romanov sheep in the Bilogora region, Croatia

The study aimed to determine the influence of air temperature, amount of precipitation and sunlight duration on the reproductive traits of the Romanov sheep in the Bilogora region, Croatia.Animals were kept in a fenced rotating pasture with access to stables during the night. Sheep were naturally mated. During three consecutive years (2019-2021), reproductive performance data were collected for four sheep flocks (n=26-57). Data on air temperature, sunlight duration, and daily precipitation volumes were obtained from the Croatian Meteorological and Hydrological Service (CMHS), Zagreb, Croatia, from the nearest meteorological recording station, located within 5-15 km of farms. A total of 425 ewes were mated, of which 399 successfully conceived and 851 lambs were born, with an average litter size of 1.63. The average fertility during the study was 93.88%. Lambing distribution was not equally distributed throughout the year as 73% of all lambs were born during winter and spring (winter 51.88%; spring 21.31%; summer 13.53% and autumn 13.28%). Sexual activity was lowest from the end of March to May, while the peak of sexual activity was from the end of August to October. There was a positive or negative correlation (P<0.0001 (Kruskall-Wallis)) between air temperature, sunshine duration and amount of precipitation with certain reproductive traits (number of pregnant and non-pregnant ewes). Daily average air temperatures were highest in summer but drop suddenly at the start of the breeding season in early autumn. Also, the day begins to shorten, and night begins to become longer which is crucial for shortday breeder species such as sheep and goats. Other factors, such as relative humidity and rainfall, can also directly or indirectly impact sexual activity and significantly affect fertility. The results indicate that air temperature, amount of precipitation, and sunlight duration during different months or seasons could influence the reproductive traits of Romanov sheep in Bilogora region, Croatia.