title: The effects of melatonin and light treatment on the reproductive performance of yearling Suffolk rams.
abstract: The effects of melatonin and light treatments on the reproductive performance of yearling Suffolk rams was investigated. One group (group A, n = 5) remained in the local light environment (lat. 51 degrees 43'N). The other two groups (group B, n = 5; group C, n = 5) were given a priming period of long days [18 h light (L):6 h dark (D)] during 26 January-9 March. During 9 March-16 October, group B was exposed to short days (9L:15D) and group C was given melatonin implants (Regulin) at 5-weekly intervals. Testis diameter, sexual behaviour and semen quality were used to assess reproductive performance. The responses of groups B and C were similar and peak reproductive performance occurred in these groups significantly earlier than in group A. Peak performance was not maintained in groups B and C throughout the short day and melatonin treatment periods and this has been attributed to refractoriness. The response of group C clearly indicates that melatonin treatment may be considered as an alternative to photostimulation for the preparation of rams for out-of-season breeding.
authors.affiliation: Royal Veterinary College, University of London, Potters Bar, Herts.
authors.forename: M
authors.initials: M
authors.lastname: Hanif
authors.forename: H L
authors.initials: HL
authors.lastname: Williams
mesh_terms: D000818:Animals; D008027:Light; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D010507:Periodicity; D011897:Random Allocation; D012098:Reproduction / Q000187:drug effects* / Q000528:radiation effects; D012756:Sheep / Q000502:physiology*
chemical_list: D008550:Melatonin