Effects of Zeranol upon luteal maintenance and fetal development in peripubertal gilts.
Eighty gilts were utilized to determine whether zeranol implants could maintain hCG-induced corpora lutea (CL) in peripubertal gilts and to examine the effects of a Zeranol implant on fetal development. Crossbred gilts (171+/-0.3 days of age, 109.1+1.4 kg) were blocked by weight and ancestry to control (n=40) or treatment (n=40) groups. To induce ovulation and CL maintenance, treated gilts received 500 IU of hCG i.m. and a Zeranol ear implant (Ralgro, 36 mg; day 0). All gilts were checked once daily for estrus with a mature boar from days 3-58 of the experiment. On day 42, treated gilts received two 10 mg injections of Lutalyse (PGF(2)alpha) spaced 6 h apart. Treated gilts not displaying estrus within 7 days of PGF(2)alpha received two additional 10 mg of PGF(2)alpha spaced 6 h apart on day 49. On days 44-58, gilts detected in estrus were inseminated twice, 24 h apart with pooled semen via AI. Blood samples were obtained on days 0, 7, 18 and 42 and analyzed for serum progesterone (P(4)). Bred gilts were slaughtered on days 58-62 of gestation. Ovulation, as determined by serum concentrations of P(4) on day 7 of the experiment, was induced by hCG in 79.5% of treated gilts. Zeranol implants, however, failed to increase (P>0.05) the proportion of gilts available for breeding (treated, 21/39; control, 18/40). Of gilts inseminated on days 44-58, 16/21 treated gilts and 16/18 control gilts were pregnant at slaughter on days 58-62 of gestation. Number of fetuses (7.5 versus 12), fetal weight (83 versus 121 g), fetal length (117 versus 132 mm) and fetal survival (45% versus 78%) were reduced (P<0.001) by Zeranol implants. These data indicate that treatment of peripubertal gilts with a 36 mg Zeranol implant did not increase the proportion of gilts available for breeding while causing deleterious effects upon the fetuses.
Trout
William E
WE
Department of Animal Sciences, Lilly Hall of Life Sciences, Purdue University, West Lafayette, IN 47907-2054, USA.
Herr
Cory T
CT
Richert
Brian T
BT
Singleton
Wayne L
WL
Haglof
Stanley A
SA
Diekman
Mark A
MA
D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D003338:Corpus Luteum / Q000187:drug effects* / Q000502:physiology; D004968:Estrogens, Non-Steroidal / Q000494:pharmacology*; D005260:Female; D010060:Ovulation / Q000187:drug effects; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D013552:Swine / Q000196:embryology* / Q000502:physiology*; D015029:Zeranol / Q000008:administration & dosage / Q000494:pharmacology*
D006063:Chorionic Gonadotropin; D004968:Estrogens, Non-Steroidal; D011374:Progesterone; D015029:Zeranol