Effects of active immunisation of female lambs against androstenedione on LH secretion, onset of puberty and ovulation rate

Ronayne, E.; Fitzsimons, J. T.; Hanrahan, J. P.; Quirke, J. F.; Roche, J

doi:10.1016/s0378-4320(05)80011-9

Cited by 6 publications

(1 citation statement)

References 21 publications

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“…Moreover, there are reports of inadequate luteal function prior to ovulation causing infertility in ewes (Hunter, 1991) and ewe lambs (Davies and Beck, 1992). Therefore, as puberty is normally preceded by a luteal phase (Ronayne, Fitzsimons, Hanrahan, Quirke and Roche, 1991) a deficiency at this time might account for the infertility observed in group A in experiment I. This cannot explain the subfertility of the animals given a single oestrogen and progestagen therapy prior to mating because this treatment would have simulated endocrine changes similar to those that occur during a normal oestrous cycle (Moore, 1988).…”

Section: Discussionmentioning

confidence: 99%

The effect of stage of breeding season or pre-mating oestrogen and progestagen therapy on fertility in ewe lambs

Beck

Davies

1994

Anim. Sci.

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An investigation was conducted to determine the effect of mating at puberty or third oestrus or after pre-mating oestrogen and progestagen therapy, designed to mimic the changes that occur in plasma oestrogen and progesterone concentrations during the 1st, 2nd or 3rd oestrous cycles, on fertility in ewe lambs. Twenty-five ewe lambs were mated at puberty on mean date of 18 October and 21 were mated at third oestrus on 3 December. Of these, 28% and 81% of animals mated at puberty and third oestrus lambed, respectively (P < 0-05). A similar number of ewe lambs were mated within 24 h of ram introduction in the groups given one, two or three consecutive applications of oestrogen and progestagen (25 fig oestradiol benzoate followed 48 h later by a progestagen pessary left in situ for 12 days). Of the 43 corpora lutea, 21 were represented by viable embryos in the 37 animals holding to service after one application compared with 34 out of 46 corpora lutea in 40 animals given three applications (P < 0-05). Furthermore, embryo crown-rump length, embryo weight and amniotic sac width was greater (P < 0-05), on day 32 of pregnancy, in animals given one compared with three applications of oestrogen and progestagen. These results demonstrate that fertility is improved in ewe lambs mated on third oestrus or after progestagen and oestrogen therapy designed to simulate three oestrous cycles.

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