Message from APHA: WELFARE RISKS regarding NOT SHEARING & Bluetongue advice
The circulating BTV3 variant in South West England has prompted discussion on social media forums leading to comments that the likelihood of midge-biting sheep and therefore BTV3 infection will be reduced in fully fleeced sheep and that farmers should not sheep their sheep to reduce risks*.
Given the current temperatures in various parts of the UK, shearing of sheep to alleviate the impacts of heat stress are paramount to meeting the welfare needs of sheep in many areas of the UK at the moment and delaying shearing until October on this basis is not acceptable when heat stress in sheep is a real risk on farm, during transport and at markets.
Economic losses associated with temperature stress in the sheep will include reduced feed intake as an adaptive response to high temperatures resulting in slow growth rate and daily body weight gain. It not only causes physiological /metabolic upsets but can affect carcass and meat quality characteristics by altering the rate and degree of postmortem muscle glycolysis and the resulting pH. In breeding sheep, heat stress will reduce mating behaviour for those being mated in early autumn, increases embryonic mortality, impairs embryo development, reduces lamb birth weight, and increases perinatal lamb mortality, not forgetting significant impacts on breeding rams sperm quality which will carry on for up to 2 months after the temperatures have reduced. The list goes on (see reference)**
Making decisions not to shear now for those not yet shorn can have not only immediate stressful impacts on day to day coping with high temperature including death from heat stress but clearly medium term impacts on marketing sheep for slaughter and medium to longer term impacts for the breeding animals
References :
*This is likely based on the evidence from research conducted during the 2023-2024 Netherlands outbreak that showed that those farmers shearing in July – September 2023 had an increased odds of more sheep being within a herd being infected for BTV in 2024 in seropositive herds (OR: 2.22, 95 % CI: 1.27–3.86) compared to shearing between January and March. One hypothesis given was that that fleece regrowth in sheep sheared earlier in the year partially prevented them being bitten by Culicoides spp. during the outbreak in late summer 2024.
However, it should be noted that this research showed that shearing sheep in spring tended to be associated with a higher probability of the flock as a whole testing BTV seropositive in 2024, compared to shearing in winter (OR: 1.6 (95% CI: 0.95–2.66)). This study also showed that flocks kept indoors as a preventive measure were four times less likely to be BTV seropositive (OR: 0.25 (95 % CI: 0.09–0.67)), compared to outside flocks.
** see this article for a useful review on heat stress and the list of further references to impacts of heat stress