Attainment of puberty by ewes in the first year of life is associated with improved reproductive performance at 2 years of age

Edwards, Sara J.; Juengel, Jennifer L.; O’Connell, Anne R.; Johnstone, P. D.; Farquhar, P. A.; Davis, G. H.

doi:10.1016/j.smallrumres.2014.11.006

Cited by 9 publications

(7 citation statements)

References 21 publications

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“…If it is assumed that 82% of ewe lambs achieve puberty at mating, then the estimated embryo survival probability increased from 0.63 to 0.82 (all flocks). If the proportion of ewe lambs that achieve puberty at mating was included as an extra parameter in the estimation procedure then the maximum likelihood estimated embryo survival probability was 0.73 and the percentage of ewe lambs achieving puberty at mating was 87% (all flocks), consistent with research flock estimates for the percentage of ewe lambs achieving puberty at mating ( Nieto et al, 2013 ; Edwards et al, 2015 ).…”

Section: Resultssupporting

confidence: 57%

“…Note that the embryo survival and ovulation rate estimates were also conditional on the assumption that all ewe lambs are ovulating at mating. Not all ewe lambs achieve puberty at mating and it has been estimated that 82% of ewe lambs achieve puberty in their first year of life in a New Zealand research flock, although this is variable between years ( Edwards et al, 2015 ) and is likely to be variable between farms. This is also consistent with the 89% of Merino ewe lambs that attained puberty at 250 d of age in a single year ( Nieto et al, 2013 ).…”

Section: Resultsmentioning

confidence: 99%

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The role of reproductive loss on flock performance: a comparison of nine industry flocks

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Edwards

Juengel

2021

Translational Animal Science

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The reproductive performance of a sheep flock is dependent on a multitude of complex interacting factors. Attaining optimal flock performance requires information about how the reproductive steps are linked and relate to readily available measurements of the state of the flock. The goal was to use data from nine commercial flocks (greater than 300,000 records) to investigate and model the key reproductive steps affecting flock reproductive performance. We also developed a maximum-likelihood based methodology to predict flock ovulation rate based on measurements of the number of fetuses at mid-pregnancy (detected by ultrasound-scanning). The model was used to determine how changes in pre-mating liveweight, age, predicted ovulation rate, number of fetuses at mid-pregnancy, lamb survival and lamb growth rate affect the total lamb liveweight at weaning per ewe exposed to the ram in each flock. The data from the commercial flocks were also used to investigate the role of ewe age and pre-mating liveweight on each reproductive step. Sensitivity analyses were conducted to identify the key reproductive steps affecting flock reproductive performance, with a focus on understanding how these steps vary between flocks. The elasticity for embryo survival was 60% of that for lamb survival for these flocks and the elasticities for ovulation rate were highly variable between flocks (0.16 − 0.50 for mature ewes). This indicates that ovulation rate was near-optimal for some flocks, whereas there was potential to significantly improve flock performance in suboptimal flocks. The elasticity for ewe pre-mating liveweight was highly variable between flocks (-0.03 to 0.84 for mature ewes and -0.18 to 1.39 for ewe lambs), indicating that pre-mating liveweight ranged from optimal to suboptimal between flocks. For these suboptimal farms, opportunity exists to increase flock performance through improved management of ewe pre-mating liveweight. Reproductive loss was significantly greater in ewe lambs than mature ewes, although the difference is dependent on the stage of reproduction and flock. Predicted ovulation rate was 25% lower for ewe lambs and there was a 30% relative decrease in the predicted embryo survival probability from ovulation to scanning for ewe lambs. There was a 10% relative decrease in lamb survival probability from birth to weaning for ewe lambs and lamb growth rate was 25% lower for ewe lambs.

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Section: Resultssupporting

confidence: 57%

Section: Resultsmentioning

confidence: 99%

The role of reproductive loss on flock performance: a comparison of nine industry flocks

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Edwards

Juengel

2021

Translational Animal Science

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“…In another study, the twinning rate was reported to increase with the LW of the ewe in Awassi sheep, where the highest rate of twin births was at 51-55 kg (Thomson and Bahhady, 1988). Heavier ewes achieved puberty in the first breeding season, had a higher number of lambs, and produced more multiples at 2 years old (Edwards et al, 2014). Kenyon et al (2014) reported a greater effect of ewe LW on reproductive performance in younger ewes than older ewes.…”

Section: Fertility Rate and Multiple Birth Ratementioning

confidence: 93%

Effects of ewe live weight and age on reproductive performance, lamb growth, and survival in Central Anatolian Merino sheep

et al. 2015

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Abstract. The aim of this study was to evaluate the effects of premating ewe weight and age on ewe reproductive performance, lamb growth and survival in Central Anatolian Merino (CAM) sheep.The trial included 4935 ewes and 5548 lambs from 23 breeder flocks in Eskişehir Province. The live weights (LWs) and ages of the ewes were recorded 1 week before the mating season. The number of lambs born, fertility rate, multiple birth rate (MBR), and lamb survival rate (SR) at days 75 and 120 were determined. The effects of the LW and age of the ewe were found to be important for the reproductive performance of ewes and for the lamb's growth rate (P < 0.05-0.001). Ewe MBRs and the birth weight (BW) and LW of the lambs at days 75 and 120 increased proportionally with the increase in LW in ewes prior to mating. The fertility rate and MBR were lower (P < 0.05-0.001) in 1.5-year-old ewes than in older ewes. However, lambs' SR at days 75 and 120 were not affected by the premating LW and age of the ewe. In summary, a better reproductive performance and lamb growth rate in CAM flocks may be achieved by the selection of breeding ewes from ewes weighing more than 60 kg.

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“…Combined, these findings indicate the importance of ensuring ewe lambs reach puberty as early as possible, within the natural breeding season, if the aim is to maximize the numbers successfully bred. Edwards and others [ 89 ] reported that two-tooth reproductive performance was also greater in those that achieve puberty as a ewe lamb, further reinforcing the importance of achieving puberty in the first year of life. Furthermore, Wall and others [ 90 ] reported increased ewe lifetime economic performance among ewes first bred at 18 months of age when they attained puberty as a ewe lamb (in their first year of life) compared to those that had not.…”

Section: Factors Affecting Ewe Lamb Performance Prior To and During B...mentioning

confidence: 94%

“…The ram effect should not be used as a tool to induce puberty in lightweight ewe lambs, as this can increase the risk of reproductive failure in later stages of pregnancy and lactation or in future years. An alternative use of vasectomized rams is to identify ewe lambs that achieve puberty, but are not subsequently bred, as a screening tool to select more fertile/fecund replacements in traditional systems where ewes are bred for the first time at an older age [ 89 ].…”

Section: Factors Affecting Ewe Lamb Performance Prior To and During B...mentioning

confidence: 99%

Breeding Ewe Lambs: An Australasian Perspective

Kenyon

Corner-Thomas

2022

Animals

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A number of potential advantages have been identified for breeding ewe lambs at 7 to 9 months of age, including increased lifetime productivity and profitability. However, breeding at this young age in extensive pastoral systems, such as in Australasia, can be associated with a number of disadvantages resulting in uptake of this management procedure being relatively low. This review highlights the known differences between ewe lamb and mature ewe reproductive performance, thus differing in their management. The review then summaries the scientific literature of factors that affect ewe lamb reproductive success, with a focus on recent studies conducted under extensive pasture-based conditions in Australasia. In particular, this review outlines the importance of ewe lamb live weight and body condition score on their productivity. The potential long-term consequences of breeding a ewe lamb at a young age in terms of her future success and that of her offspring to weaning are briefly outlined. In addition, the potential impacts of selecting progeny born to ewe lambs as future replacement ewes are discussed. Throughout this review, optimal management guidelines from prior to breeding the ewe lambs until rebreeding at 2 years of age are provided. Lastly, areas requiring future research are identified and discussed.

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Attainment of puberty by ewes in the first year of life is associated with improved reproductive performance at 2 years of age

Cited by 9 publications

References 21 publications

The role of reproductive loss on flock performance: a comparison of nine industry flocks

The role of reproductive loss on flock performance: a comparison of nine industry flocks

Effects of ewe live weight and age on reproductive performance, lamb growth, and survival in Central Anatolian Merino sheep

Breeding Ewe Lambs: An Australasian Perspective

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