Effect of melatonin treatment on fertility, fecundity, litter size and sex ratio in ewes

G. Bonev
Abstract. The current study was designed to investigate the effects of administering melatonin alone on reproductive performance and inducing estrus in ewes during anestrous season. In the experiment a significant effect of breed and time of melatonin implants treatment was recorded for fertility, litter size (number of lambs born per ewe) and fecundity in the three breeds under study. Melatonin treatment increased the fertility rate significantly in the two spring treatment periods: March – ewes Group I and IV), and April – ewes Group II in the Pleven Blackhead x Awassi and Ile de France flocks. Regarding litter size, the melatonintreated ewes recorded a significantly higher number of lambs born after treatment in March in the meat breed. The lower result (115% fecundity) was obtained in experimental Group III (Awassi). The melatonin implants improved the fertility in the ewes when inserted in spring (II-94,5%; III – 93,26%; IV – 91,42% ). The highest increment in the number of lambs born per ewes treated in these three breeds was obtained in April – Farm 2. The litter size frequency for the three breeds under study were: (0) 5%, (1) 57,964%, (2)36%, (3) 1,036%. Of particular interest was the frequency of litter size and sex ratios of newborn lambs.