Sheep & Goats

Genetic and non-genetic factors associated with ewe culling

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Abstract

Culling refers to the deliberate removal of an ewe from the flock and can be classified as voluntary (management decision) or involuntary (unplanned decision). Premature removal of ewes from a flock not only increases female replacement costs but reduces flock productivity through a reduction in ewe output; impacting both economic and environmental flock sustainability. Understanding the reasons, and genetic variability, for ewe culling is essential to enhance flock performance and optimise longevity. The objectives of this study were to examine the factors associated with voluntary and involuntary culling and to estimate the genetic variance for ewe culling. A total of 9,207 ewe culling records from 3,845 ewes collected between 2005 and 2025 were available from a large multibreed Irish research flock. Ewe culling events were recorded within the associated production year. Variance components and risk factors associated with the logit of the probability of ewe culling were modelled using threshold model for ewe culling in ASReml, with an additive ewe effect included as random effect. Potential risk factors included year of culling record, ewe parity, ewe breed composition, ewe heterosis and recombination coefficients and ewe litter size for year of culling record. Over the 20-year period, the mean prevalence of culling was 21.46% (SD = 0.41). A total of 38.81% of ewes had no recorded culling reason, of the ewes with an identified culling reason, age (30.85%), mastitis (26.88%) and udder health (13.23%) were most prevalent. Overall, 58.2% of culling events were classified as involuntary, while 41.8% were voluntary. The individual culling of ewes occurred most frequently at pre-mating (36.12%), post-weaning (19.56%), or following pregnancy scanning (20.03%).Risk factors associated with ewe culling differed by year of culling, parity, ewe litter size, heterosis coefficient and breed (P< 0.001). The predicted probability of an ewe culling increased (P < 0.001) annually from 0.18 (2009) to 0.41 (2025). Ewes that did not rear a lamb within the year of culling had the greatest predicted probability (0.73) of being culled, ewes with single lambs had the lowest predicted probability (0.31) of being culled (P< 0.001). The probability of an ewe being culled increased with ewe parity from 0.09 in first parity to 0.88 in seventh parity (P< 0.001). The greatest predicted ewe culling incidence was recorded in Belclare ewes, while the lowest incidence was recorded in Suffolk ewes (P< 0.001). The genetic standard deviation of ewe culling was 0.69, the direct heritability estimated using the threshold model for ewe culling was 0.13 (0.02). Results from this study highlight that ample genetic variation exists for ewe culling. Knowledge of the animal-level factors associated with ewe culling and the appropriate management of different risk categories could be used to reduce ewe culling on farm.

Keywords: 2026

How to Cite:

Mahony, A., McGovern, F., McHugh, N., Pabiou, T., Purfield, D. & Walsh, H., (2026) “Genetic and non-genetic factors associated with ewe culling”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286592. doi: https://doi.org/10.31274/wcgalp.24060

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