title: Evaluation of the influence of melatonin implants during the gestation period in sheep from a selenium-deficient region.
abstract: OBJECTIVE
  To evaluate the possible effect of melatonin implants on blood glutathione peroxidase (GSHPx) activity and in the prevention of selenium (Se)-responsive disorders in sheep from an Se-deficient region.
  
  
  METHODS
  Randomized controlled clinical trial.
  
  
  METHODS
  100 Merino ewes.
  
  
  METHODS
  Ewes of the same age, parity, body weight, body condition, and reproductive and health history were randomly allotted to 1 of 2 groups (control and implanted) of 50 sheep each. Treatment consisted of implants of melatonin (18 g) administered SC in the pinna of the right ear 6 weeks prior to introduction of rams. The control group did not receive implants. Hematologic and serum biochemical analyses were performed at various points before and after treatment, in addition to determinations of erythrocyte mean corpuscular fragility (MCF) and blood GSHPx activity. The incidence of Se-responsive disorders in lambs was recorded in both groups.
  
  
  RESULTS
  Hematologic and serum biochemical analyses yielded values within respective reference ranges for both groups. Significant differences between groups were evident in MCF at early mating (lower in the implanted group vs the control group) and in blood GSHPx activity at early mating, gestation, and early lambing (higher in the implanted group vs the control group). There were significantly fewer lambs with nutritional myodystrophy in the implanted versus the control group.
  
  
  CONCLUSIONS
  Use of melatonin implants in sheep may improve reproductive performance and yield an earlier start of breeding season. The stimulating effect of melatonin on GSHPx activity may protect against oxidative damage during the first stage of gestation.
authors.affiliation: Department of Animal Medicine, University of Extremadura, Campus Universitario, 10071, Cáceres, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Andrés
authors.forename: Joaquín
authors.initials: J
authors.lastname: Sánchez
authors.forename: Antonio
authors.initials: A
authors.lastname: Jiménez
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D004343:Drug Implants; D005260:Female; D005979:Glutathione Peroxidase / Q000097:blood; D008550:Melatonin / Q000008:administration & dosage* / Q000494:pharmacology*; D011247:Pregnancy; D012621:Seasons; D012643:Selenium / Q000172:deficiency*; D012756:Sheep; D012757:Sheep Diseases / Q000517:prevention & control*
chemical_list: D004343:Drug Implants; D005979:Glutathione Peroxidase; D012643:Selenium; D008550:Melatonin