Limits on hogget lambing: the fertility of the young ewe

Edwards, Sara J.; Juengel, Jennifer L.

doi:10.1080/00288233.2016.1253592

Cited by 19 publications

(14 citation statements)

References 73 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The model components are outlined in the following sections, which are based on the relationships used to investigate the reproductive performance of a research flock ( Shorten et al, 2020 ). The reproductive performance of ewe lambs is lower than that of mature ewes ( Edwards and Juengel, 2017 ) and therefore separate models were considered for ewe lambs and mature ewes. Ewe age ( A ) terms are omitted from each equation for the ewe lamb models.…”

Section: Methodsmentioning

confidence: 99%

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

Shorten

Edwards

Juengel

2021

Translational Animal Science

View full text Add to dashboard Cite

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.

show abstract

Section: Methodsmentioning

confidence: 99%

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

Shorten

Edwards

Juengel

2021

Translational Animal Science

View full text Add to dashboard Cite

show abstract

“…Rearing additional replacement hoggets to a productive age (or purchasing additional replacements) incurs a number of costs [ 1 , 2 , 7 ], including fewer sale lambs, increased management and feed costs, reduced selection pressure, potential biosecurity risks and increased greenhouse gas emissions. In addition, the reproductive performance of ewes increases as they age [ 8 ], so having an unnecessarily high proportion of younger ewes in a flock, due to increased wastage, reduces overall flock productivity due to a lower average flock age [ 1 ]. Using a bioeconomic model, Farrell reported that for a New Zealand North Island Hill Country sheep farm with 21% of the flock lost annually due to wastage, a reduction in wastage to 5% could increase cash profit by 33% [ 1 ].…”

Section: Introductionmentioning

confidence: 99%

Ewe Wastage in New Zealand Commercial Flocks: Extent, Timing, Association with Hogget Reproductive Outcomes and BCS

Flay

Ridler

Compton

et al. 2021

Animals

View full text Add to dashboard Cite

Ewe wastage is the combination of on-farm mortality and premature culling. Internationally, there is limited research on actual wastage incidence and causes in commercial sheep flocks. To the authors’ knowledge, this is the first study that reports both lifetime wastage and detailed annual wastage in a sample of commercial New Zealand flocks. This study utilized data collected from 13,142 ewes from four cohorts on three commercial New Zealand farms (Farm A 2010-born, Farm A 2011-born, Farm B, Farm C), during the period 2011–2017, as they aged from replacement hoggets to 6-year-old ewes (Farm A and Farm B) or 3-year-old ewes (Farm C). Data collection visits occurred at three or four key management times each year, namely pre-mating, pregnancy diagnosis, pre-lambing and weaning. At each visit, body condition score (BCS) was assessed and any ewes that were culled or had died on farm were recorded. As this was a lifetime study, each ewe was assigned an outcome and corresponding ‘exit age’. By the end of the study, all ewes that had exited their respective flocks, were classified as either prematurely culled, or dead/missing, or if still in the flock, as censored, and either the exact date or interval in which they exited the flock was recorded. Semi-parametric competing risk (premature culling vs. dead/missing), interval-censored survival models were developed to: 1. describe the association between hogget reproductive outcomes and risk of subsequent wastage, and 2. assess pre-mating BCS as a predictor of wastage in that production year. Of the 13,142 enrolled ewes, 50.4% exited their respective flocks due to premature culling and 40.0% due to on-farm dead/missing, giving a total of 90.4% that exited due to wastage. Annual mortality incidence ranged from 3.5 to 40.2%. As a hogget, wastage incidence ranged from 7.6 to 45.4%. Pregnancy or rearing a lamb as a hogget did not increase risk of subsequent wastage. In all years, pre-mating BCS was a predictor of ewe wastage, with odds of wastage lower with increasing BCS. Therefore, farmers should focus on improving pre-mating BCS to 3.5/5.0 by assessing ewe BCS at weaning, allowing poorer-BCS ewes to be managed to gain BCS before re-breeding.

show abstract

“…Breeding ewe lambs at 7 to 10 months of age can increase lifetime reproductive performance [ 1 , 2 ] and farm profitability [ 3 , 4 , 5 ]. The number of offspring weaned from ewe lambs is highly variable and generally poor in comparison to older ewes [ 6 , 7 , 8 , 9 ]. Ewe lambs that are heavier at breeding due to improved nutrition pre- and post-weaning consistently achieve higher fertility and reproductive rates, although the responses vary significantly between individual flocks and breeds [ 10 , 11 , 12 , 13 , 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

The Number of Offspring Weaned from Ewe Lambs Is Affected Differently by Liveweight and Age at Breeding

Thompson

Bowen

Keiller³

et al. 2021

Animals

View full text Add to dashboard Cite

In this paper, we tested the hypothesis that ewe lambs that are heavier and older at breeding will wean more offspring, due to increased reproductive rate and offspring survival and lower maternal mortality. To test this hypothesis, we analyzed data from more than 11,500 maternal composite ewe lambs collected over eight years. The ewe lambs had full pedigree records including birth type, age and liveweight at breeding plus records of the birthweight and survival of their offspring and the dam. The average liveweight and age at breeding was 40.2 kg and 228 days. The reproductive rate and weaning rate responses to liveweight at breeding were curvilinear (p < 0.001), and if ewe lambs achieved 45 kg by the start of breeding, their reproductive rate and weaning rate were within 5% of their maximum. By contrast, the effects of age at breeding on weaning rate was linear and increased by 0.4% per day, despite a quadratic (p < 0.01) effect of age at breeding on reproductive rate which increased only marginally when ewe lambs were older than 8 months at breeding. Increasing liveweight (p < 0.05) or age (p < 0.001) at breeding increased survival of their offspring, however an extra 10 kg of liveweight or 30 days of age at breeding increased offspring survival by less than 5%. Both liveweight (p < 0.001) and age (p < 0.01) at breeding also influenced survival of the ewe lamb dam but survival rates exceeded 95% across the range in liveweights from 30 to 55 kg and ages from 6 to 9 months. This understanding of the trade-off between age and liveweight at breeding will assist farmers to optimize the management of their ewe lambs, given the earlier they can be bred successfully the easier they can be integrated with the breeding of the adult ewe flock the following year.

show abstract

Limits on hogget lambing: the fertility of the young ewe

Cited by 19 publications

References 73 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

Ewe Wastage in New Zealand Commercial Flocks: Extent, Timing, Association with Hogget Reproductive Outcomes and BCS

The Number of Offspring Weaned from Ewe Lambs Is Affected Differently by Liveweight and Age at Breeding

Contact Info

Product

Resources

About