Regulation of puberty and reproduction in female lambs: A review

Quirke, J. F.

doi:10.1016/0301-6226(81)90029-4

Cited by 34 publications

(17 citation statements)

References 80 publications

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“…Similar to these results, it has been reported that the incidence of silent ovulations is also greater in lambs than in mature ewes during the normal onset of the breeding season (Quirke, 1981). It has been proposed that the sensitivity of the hypothalamus-pituitary axis to the increase of estrogens may be lower in lambs that in mature ewes (Whyman, 1978).…”

Section: Discussionsupporting

confidence: 72%

Reproductive response of mature and nulliparous yearling ewes to the ram effect during the non-breeding season

Ungerfeld

2016

Small Ruminant Research

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Section: Discussionsupporting

confidence: 72%

Reproductive response of mature and nulliparous yearling ewes to the ram effect during the non-breeding season

Ungerfeld

2016

Small Ruminant Research

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“…In addition, the ewes that conceived presumably did so during the second or third cycle after their first oestrus, as observed by Hare and Bryant (1985). The remainder of the ewes were detected in oestrus by either teasers or rams but failed to conceive, perhaps reflecting low quality of ovum or a high incidence of prenatal mortality (Quirke, 1981;McMillan and McDonald, 1985). Despite this problem, it is clear that genetic strategies that increase growth rate will not only advance puberty but also result in greater fertility and reproductive rate in Merino ewe lams.…”

Section: Discussionmentioning

confidence: 89%

Selection for superior growth advances the onset of puberty and increases reproductive performance in ewe lambs

Ariza-Nieto

Ferguson

Macleay

et al. 2013

Animal

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The reproductive efficiency of the entire sheep flock could be improved if ewe lambs go through puberty early and produce their first lamb at 1 year of age. The onset of puberty is linked to the attainment of critical body mass, and therefore we tested whether it would be influenced by genetic selection for growth rate or for rate of accumulation of muscle or fat. We studied 136 Merino ewe lambs with phenotypic values for depth of eye muscle (EMD) and fat (FAT) and Australian Sheep Breeding Values at post-weaning age (200 days) for live weight (PWT), eye muscle depth (PEMD) and fat depth (PFAT). First oestrus was detected with testosterone-treated wethers and then entire rams as the ewes progressed from 6 to 10 months of age. Blood concentrations of leptin and IGF-I were measured to test whether they were related to production traits and reproductive performance (puberty, fertility and reproductive rate). In total, 97% of the lambs reached first oestrus at average weight 39.4 6 0.4 kg (mean 6 s.e.m.) and age 219 days (range 163 to 301). Age at first oestrus decreased with increases in values for PWT (P , 0.001), and concentrations of IGF-I (P , 0.05) and leptin (P , 0.01). The proportion of ewe lambs that achieved puberty was positively related with increases in values for EMD (P , 0.01), FAT (P , 0.05) or PWT (P , 0.01), and 75% of the ewe lambs were pregnant at average weight 44.7 6 0.5 kg and age 263 days (range 219 to 307). Ewe lambs that were heavier at the start of mating were more fertile (P , 0.001) and had a higher reproductive rate (P , 0.001). Fertility and reproductive rate were positively correlated with increases in values for EMD (P , 0.01), FAT (P , 0.05), PWT (P , 0.01) and leptin concentration (P , 0.01). Fertility, but not reproductive rate, increased as values for PFAT increased (P , 0.05). Leptin concentration increased with increases in values for EMD (P , 0.001), FAT (P , 0.001), PWT (P , 0.001), PEMD (P , 0.05) and PFAT (P , 0.05). Many of these relationships became non-significant when PWT or live weight was added to the statistical model. We conclude that selection for genetic potential for growth can accelerate the onset of puberty and increase fertility and reproductive rate of Merino ewe lambs. The metabolic hormones, IGF-I and leptin, might act as a physiological link between the growing tissues and the reproductive axis.Keywords: ewe lambs, phenotypic selection, ASBV, reproductive efficiency ImplicationsGenetic selection can improve the rates of growth and muscle development in sheep, and should also permit reproduction at a younger age because the onset of puberty depends on attainment of sufficient body mass. Our data support this hypothesis, suggesting that phenotypic and genetic selection for growth or muscling will improve the reproductive performance of Merino ewes mated to lamb at 1 year of age. These findings will inform bio-economic models and promote genetic selection strategies with a view to improving profitability of sheep production systems by achieving improvements i...

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“…Typically, some 20 to 40% of animals mated during the breeding season remain barren, although lambing peformance does vary with breed, management and environmental factors (Quirke, 1981;Dyrmundsson, 1983). Furthermore, the vast majority of animals produce singletons and multiple births are relatively uncommon (Dyrmundsson, 1973).…”

Section: Introductionmentioning

confidence: 99%

A comparison of ovulation rate and late embryonic mortality in ewe lambs and ewes and the rôle of late embryo loss in ewe lamb subfertility

Beck

Davies

1996

Anim. Sci.

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An investigation was conducted to compare late embryonic losses in ewe lambs and ewes and to determine the effect of inducing embryonic mortality on day 15 of pregnancy on reproductive function in ewe lambs. Ovulation rate and embryo survival were determined, at 15 and 30 days after mating, in a total of 83 ewe lambs and 67 ewes. Ovulation rate was lower, at spontaneous oestrus, in ewe lambs (1-07) than in ewes (1-25; P < 0-05). There was no difference in embryo survival at day 15, as 79% of ewe lambs and 80% of ewes contained expanded conceptuses. However, embryo survival was lower in ewe lambs (69%) than ewes (88%) at day 30 (¥ < 0-05). Embryonic mortality was induced in an additional 18 ewe lambs with an intrauterine injection of colchicine on day 15 post mating. Four of these animals had normal length oestrous cycles, six had inter-oestrus intervals ranging from 22 to 35 days and eight did not return to oestrus. Overall, the results of this study demonstrate that low ovulation rate and late embryonic losses make a significant contribution to subfertility in ewe lambs. Moreover, conceptus death is associated with luteal persistence, which may reduce reproductive performance by preventing remating.

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Regulation of puberty and reproduction in female lambs: A review

Cited by 34 publications

References 80 publications

Reproductive response of mature and nulliparous yearling ewes to the ram effect during the non-breeding season

Reproductive response of mature and nulliparous yearling ewes to the ram effect during the non-breeding season

Selection for superior growth advances the onset of puberty and increases reproductive performance in ewe lambs

A comparison of ovulation rate and late embryonic mortality in ewe lambs and ewes and the rôle of late embryo loss in ewe lamb subfertility

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