The effect of the oily solution of melatonin crystal administered subcutaneously on oestrus response and conception rates in ewes

Sheep are seasonal polyestric animals. Photoperiod is the most important environmental factor that plays a role in this reproductive mechanisms. Melatonin which secreted from the pineal gland through the photoperiod stimulates oestrus and mating behaviors in sheep. The aim of this study is to investigate the effects of oily solution of melatonin crystal injected subcutaneously (SC) in different doses in 2-3 years old, healthy, multiparous sheep in the anoestrus period on serum melatonin and prolactin levels, estrus occurrence, mating, conception and pregnancy rates. The study group consisted of 280 sheep with an equal number of sheep in each group. Sheep were divided into 5 groups as MEL10 (10mg melatonin /n=70), MEL20 (20mg melatonin/n=70), MEL40 (40mg / n=70), placebo (n=70) and control (n=70) groups. Melatonin groups were injected with an oily solution of melatonin crystal as SC at different doses 11 days before the introduction of ram introduce, while only the oily solution was injected in the placebo group. No treatment was made to the control group. Blood samples were collected from all groups before the melatonin injection and on the 11th day after the injection. Estrus observations were made at 1-15, 15-30, and 30-60-day periods following the introduction of ram introduce. Reproductive parameters' data were kept. According to these data, it was determined that the melatonin level in the blood samples collected before and after the injection increased in the MEL10 (P=0.045) and MEL20 (P=0.0359) groups, while it decreased in the other groups. In addition, it was observed that the prolactin level decreased in the second blood samples collected in all groups (P>0.05). In the MEL10, MEL20, MEL40, placebo and control groups, the estrus rate was 75.71% - 58.57% - 54.28% - 51.42% - 52.85%, respectively; mating rate 61.42% - 57.14% - 52.85% - 48.57% - 50%; pregnancy rate 60% -52.85% - 42.85% - 41.42% - 38.57%; conception rate was determined as 97% - 92% - 81% - 85% - 77%. In line with the data obtained, it was observed that more effective results were obtained in the MEL10 and MEL20 groups. In conclusion; By subcutaneous injection of melatonin in appropriate doses to sheep, the breeding season can be imitated indirectly, heats can be stimulated and mating can be delayed. In addition, pregnancy and conception rates can be increased. It is thought that this method may be an alternative to melatonin implants or different synchronization methods in the future.