Effects of oestradiol benzoate injections, exposure to the boar and age on the attainment of puberty in the gilt
Yang, H.; Hughes, P.E.; Rodway, R.G.; Varley, M.A.
Veterinary Record 122(11): 257-259
1988
ISSN/ISBN: 0042-4900 PMID: 3369056 Document Number: 309628
Thirty Large White cross Landrace prepubertal gilts from five litters were allocated at random within litters to one of six treatments. All the gilts were given three daily i.m. injections of 6 micro g/kg live weight of oestradiol benzoate, the first injection being given at 100 days old or at 20 day intervals thereafter up to 200 days in the 6 treatment groups. From the time the first oestrogen injection was given, until the end of the experiment, the gilts were allowed daily contact with a boar for 20 minutes. The gilts were mated with a mature boar at the appearance of the second oestrus and they were slaughtered 20 days later. The numbers of gilts ovulating in the treatment groups were determined from plasma progesterone concentrations measured twice weekly throughout the experiment. The numbers of gilts ovulating within 10 days of the oestradiol benzoate injections were 3 of 5, 1 of 5, 0, 0, 3 of 5 and 1 of 5, respectively, in the groups first treated at 100, 120, 140, 160, 180 and 200 days old. For those gilts which were successfully mated, no significant differences were observed between the treatment groups in the number of viable embryos per gilt.