title: Observations on the influence of active immunization against somatostatin on the reproductive performance of sheep and pigs.
abstract: Somatostatin (SRIF) is known to have inhibitory effects in a wide variety of tissues but a role in reproduction has not been described. The present studies describe the influence of SRIF immuno-neutralization on the reproductive performance of sheep and pigs. In experiment 1, Rambouillet x Suffolk ewe lambs were actively immunized against SRIF conjugated to ovalbumin (SI; n = 24) or were not immunized (CT; n = 32). Primary immunizations were initiated at weaning and boosters given at 4-week intervals, as well 10 days before breeding and lambing. Over two years, breeding periods were September and January (in-season) and May (out-of-season). Pregnancy rates were higher for SI than for CT ewes following both in-season (P less than 0.01) and out-of season breeding (P less than 0.06). The number of lambs born per ewe lambing was not affected by treatment. In experiment 2, Yorkshire x Landrace gilts were actively immunized against SRIF-ovalbumin conjugate (n = 37) or were not immunized (n = 38). Primary immunizations were given at 39.8 +/- 1.5 kg body weight and boosters after 4 weeks, 10 days before breeding and at 105 days of gestation. Some SI (n = 15) and CT gilts (n = 17) were slaughtered 10 days after estrus to determine ovulation rates. Remaining SI (n = 22) and CT (n = 21) gilts carried their litters to term. Ovulation rates tended to be higher (P less than 0.1) in SI than CT gilts (11.8 +/- 0.6 vs. 10.7 +/- 0.4). There was no effect of treatment on pregnancy rates to initial breeding (86.4 vs. 90.5% for SI and CT gilts, respectively) but first litter size tended to be larger (P less than 0.07) for SI than for CT gilts (9.95 +/- 0.34 vs. 9.00 +/- 0.38). There was no effect of treatment on litter growth performance during lactation. These data provide evidence that SRIF may be involved in the regulation of reproduction.
authors.affiliation: Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada.
authors.forename: R N
authors.initials: RN
authors.lastname: Kirkwood
authors.forename: R S
authors.initials: RS
authors.lastname: Korchinski
authors.forename: P A
authors.initials: PA
authors.lastname: Thacker
authors.forename: B
authors.initials: B
authors.lastname: Laarveld
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development; D000906:Antibodies / Q000032:analysis; D012098:Reproduction / Q000276:immunology / Q000502:physiology*; D012756:Sheep / Q000276:immunology / Q000502:physiology*; D013004:Somatostatin / Q000276:immunology*; D013552:Swine / Q000276:immunology / Q000502:physiology*; D014611:Vaccination / Q000662:veterinary*
chemical_list: D000906:Antibodies; D013004:Somatostatin