title: Reproductive and endocrine characteristics of delayed pubertal ewe-lambs after melatonin and L-tyrosine administration.
abstract: The investigation was carried out to study the impact of melatonin and L-tyrosine administration on the onset of cyclicity in delayed pubertal ewe-lambs. Fifteen delayed pubertal ewe-lambs (age >16 months) were used in this study after being assigned randomly into three groups. In the first group (melatonin treated group, n = 5), each lamb was administered 3 mg melatonin orally at 16:00 hours from 1 July to 15 September while in the second group (L-tyrosine treated group, n = 5), each lamb was administered L-tyrosine at the level of 100 mg/kg b.w. as a single oral dose. The third group (n = 4) served as control. Lambs were exposed to mature, fertile rams daily and blood samples were collected twice weekly. The progesterone concentrations (P4 evaluations) were significantly higher (p < 0.05) in treated groups than the control group. Ovarian activity, assessed by P4 evaluations, showed that all animals in the first group came in oestrus and from them four got pregnant (80%) while in the second group, only three lambs came in heat and from them two became pregnant (40%). On the contrary, none of the control lambs showed oestrus. In conclusion, this study confirmed that the oral administration of melatonin and L-tyrosine played an essentially physiological roles to induce cyclicity in delayed pubertal ewe-lambs and improved their reproduction.
authors.affiliation: Department of Animal Reproduction and Artificial Insemination, National Research Center, Dokki, Giza, Egypt. ekhairi@gmx.at
authors.forename: K A
authors.initials: KA
authors.lastname: El-Battawy
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D004971:Estrus / Q000187:drug effects*; D005260:Female; D008550:Melatonin / Q000008:administration & dosage* / Q000494:pharmacology; D010507:Periodicity; D011374:Progesterone / Q000097:blood; D011897:Random Allocation; D012741:Sexual Maturation / Q000187:drug effects*; D012756:Sheep / Q000502:physiology*; D014443:Tyrosine / Q000008:administration & dosage* / Q000494:pharmacology
chemical_list: D014443:Tyrosine; D011374:Progesterone; D008550:Melatonin