Comparison on the Response of Ewes to the “Ram Effect” in Seven Bulgarian Breeds

K. NEDELKOV1, N. TODOROV2, D. GIRGINOV1 and М. SIMEONOV3
1 Trakia University, Faculty of Veterinary Medicine, Department of Animal Husbandry, BG - 6000 Stara Zagora,Bulgaria
2 Trakia University, Faculty of Agriculture, Department of Animal Physiology, Morphology and Nutrition,BG - 6000 Stara Zagora, Bulgaria
3 Institute of Forage Crops, BG - 5800 Pleven, Bulgaria

Abstract

NEDELKOV, K., N. TODOROV, D. GIRGINOV and М. SIMEONOV, 2015. Comparison on the response of ewes to the “ram effect” in seven Bulgarian breeds. Bulg. J. Agric. Sci., 21: 189-192

In Bulgaria no experiments have been conducted to study the response rate of local breeds to the “ram effect”. The aim of the present study was to compare the degree of synchronization of oestrus by using the “ram effect” in some of the widely distributed sheep breeds in Bulgaria. For this purpose there were conducted 8 experiments with seven typical Bulgarian breeds: Bulgarian Dairy Synthetic Population Sheep (BDSP), West Stara Planina Sheep (WSPS), Central Stara Planina Sheep (CSPS), Tsigai, Karakachan Sheep (KS), Pleven Blackhead Sheep (PBS), Karnobat Fine-wool Sheep (KFWS) and a total number of 4506 ewes. Rams, equipped with aprons to prevent breeding of oestrus ewes, were used as teasers and also as stimulators of sexual functions of ewes. The synchronising “ram effect” was established by the characteristic peaks in the dynamics of ewes in oestrus and inseminated ewes which were observed between the 16th and 26th after placing teaser rams in the flocks. It was found that all seven Bulgarian breeds responded to the “ram effect” with typical two peaks within there were inseminated between 34.7 and 76% of ewes. From the comparison between different breeds it appeared that the differences were mainly connected with the technique of conducting synchronization, body condition score (BCS) of ewes, level of nutrition and other factors (climatic, grazing conditions, management and etc.) rather than with the breed characteristics. Significantly higher rate of response was established in the experiment conducted with Pleven Blackhead Sheep. The reasons were the lack of fertilization of ewes in oestrus during the first 15 days of the contact with rams, providing an optimal BCS and activation of ram libido before introduction into the flock.

Key words: Bulgarian sheep breeds, ram effect, comparison, response rate, oestrus synchronization

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