EFFECT OF MELATONIN ON THE REPRODUCTIVE CHARACTERISTICS OF RAMS OF NORTH EAST BULGARIAN FINE FLEECE BREED

Some ruminant species, including sheep, show a markedly seasonal breeding cycle. There is evidence for the practical use of the pineal hormone melatonin to improve reproduction in sheep but the mechanism of action of the hormone in rams is less known. Studies have shown significant breed differences as a result of its application. The purpose of this study is to obtain more comprehensive data about the effects of melatonin on the fertility of rams of Northeastern Bulgarian fine fleece breed characterized by a marked seasonal cycle of reproduction. Detailed andrological studies involving the breed are absent and no statements and results of studies published on this subject could be found in the literature so far. We tested the capabilities of melatoninadministered both by diet and injection of a subcutaneous implant containing the hormone (Melovin, Ceva Animal Health, France). Dilution of semen was made using thinner buffer base containing a combination of carbohydrates. Results show increased motility, increased survival and a decrease in the percentage variation in the ejaculate pathological forms in the treated animals. Slightly better results are obtained from the implanted animals compared to rams receiving hormone alimentary. Protecting and promoting properties of the hormone are important for the reproductive capacity and improve the reproductive performance of rams. Results and statements presented in this study can be used mainly by livestock rearing this breed, but the experience learned from the research will also be useful for farmers working on breeding and other local Bulgarian sheep breeds.