The Association Between Variation in the Seasonal Onset of Oestrus and Litter Size in the Ewe

Hendy, C. R. C.; Bowman, J. C.

doi:10.1530/jrf.0.0400105

Cited by 15 publications

(8 citation statements)

References 6 publications

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“…(1974) that fertility is higher at third oestrus than at puberty. Furthermore, they agree with earlier reports of an increase in fertility during the early part of the breeding season in ewe lambs (Hare and Bryant, 1985) and ewes (Lees, 1978;Hendy and Bowman, 1978). In addition, these results extend earlier observations by demonstrating that mating ewe lambs at third oestrus rather than puberty, will significantly improve lambing performance.…”

Section: Discussionsupporting

confidence: 92%

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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Section: Discussionsupporting

confidence: 92%

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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“…Hendy and Bowman (1974) suggested that good body condition is associated with earliness of breeding but this proposition was not supported by Ducker and Boyd (1974) who could demonstrate no difference in the mean date of first oestrus for Greyface ewes differing in live weight by 14-3 kg. Hendy and Bowman (1974) suggested that good body condition is associated with earliness of breeding but this proposition was not supported by Ducker and Boyd (1974) who could demonstrate no difference in the mean date of first oestrus for Greyface ewes differing in live weight by 14-3 kg.…”

Section: Discussionmentioning

confidence: 97%

“…In a prolific genotype, Hendy and Bowman (1974) associated early oestrus onset with high litter size and demonstrated a progressive increase in litter size from the first to the third oestrous cycle of the breeding season. These data suggest that ovulation rate increases over this time but no such increase could be demonstrated by Sweeney and O'Callaghan (1996) who measured ovulation rate during each of the first five cycles of the breeding season in crossbred ewes.…”

Section: Discussionmentioning

confidence: 99%

Influence of lambing date on subsequent ovarian cyclicity and ovulation rate in ewes

Mitchell¹,

King²,

Aitken³

et al. 1997

Anim. Sci.

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Link to this article: http://journals.cambridge.org/abstract_S1357729800016325How to cite this article: L. M. Mitchell, M. E. King, R. P. Aitken and J. M. Wallace (1997). Inuence of lambing date on subsequent ovarian cyclicity and ovulation rate in ewes. AbstractThe effect of lambing date on the subsequent onset and duration of ovarian cyclicity in Mule (Bluefaced Leicester X Scottish Blackface) ewes was investigated. Nineteen ewes which had lambed in January (16 January 1993 (s.e (14 May 1993 (s.e. 2 days)) and been weaned on 23 August were maintained at pasture as two isolated groups. A raddled vasectomized ram was continually present with each group from 14 July 1993 to 26 May 1994 and marked (oestrous) ewes were recorded twice weekly. Ovarian activity was assessed by measuring peripheral progesterone concentrations in blood samples collected twice weekly and by laparoscopic viewing of the ovaries of all ewes during October, January and March. The onset and duration of ovarian activity were significantly affected by the previous lambing date. For January and May lambing ewes, mean dates of onset were 5 September 1993 (s.e. 2 days) v. 25 September 1993 (s.e. 4 days) (P < 0-001) and of cessation were 5 April 1994 (s.e. 5 days) v. 10 April 1994 (s.e. 3 days). Mean durations of ovarian activity were 212 (s.e. 6) and 195 (s.e. 5) days (P < 0-05) during which 12-4 (s.e. 0-29) and 11-5 (s.e. 0-38) ovarian cycles respectively were recorded. Ovulation rate was not affected by previous lambing date but was significantly lower in March compared with October (January lambing ewes 1-7 (s.e. 0-1) v. 2-3 (s.e. 0-1) (P < 0-001); May lambing ewes 1-6 (s.e. 0-1) v. 2-1 (s.e. 0-1) (P < 0-01)). Results demonstrate that (i) Mule ewes have a potential breeding season of up to 8 months duration; (ii) the onset and duration of ovarian activity can be influenced by previous lambing date; and (Hi) a seasonal decline in ovulation rate may, in practical terms, result in a lower lambing percentage for animals bred towards the end of their natural breeding period. . 3 days)) and been weaned in February-March and 22 comparable ewes which had lambed in May

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“…It would therefore appear that the artificial photoperiod was effective in eliminating the natural seasonal variation (Hendy & Bowman, 1974) in ovulation rate.…”

Section: Discussionmentioning

confidence: 99%

Ovulation and embryo survival rates and plasma progesterone concentrations of prolific ewes treated with PMSG

Rhind¹,

Robinson²,

Fraser³

et al. 1980

Reproduction

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Finnish Landrace x Dorset Horn ewes of two flocks comprising 47 and 51 animals were mated to Suffolk rams at a synchronized oestrus on 9 December (Flock D) and 8 April (Flock A) after treatment with 500 i.u. PMSG. The ewes were slaughtered between 50 and 145 days of pregnancy. The mean +/- s.e.m. ovulation rates were 4.5 +/- 0.24 (Flock D) and 5.0 +/- 0.32 (Flock A) for ewes which conceived to the induced oestrus and the corresponding litter sizes were 2.8 +/- 0.15 and 2.8 +/- 0.18. Mean concentrations of progesterone in the peripheral plasma during pregnancy were higher for Flock D than for Flock A ewes both in early (P less than 0.001) and late (P less than 0.05) pregnancy. An increase in ovulation rate, up to 4 or 5, was associated with an increase in mean litter size. There was evidence that higher ovulation rates were counterproductive.

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The Association Between Variation in the Seasonal Onset of Oestrus and Litter Size in the Ewe

Cited by 15 publications

References 6 publications

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

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

Influence of lambing date on subsequent ovarian cyclicity and ovulation rate in ewes

Ovulation and embryo survival rates and plasma progesterone concentrations of prolific ewes treated with PMSG

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