Investigating Mastitis In Meat-Producing Sheep: Incidence, Prevalence, and Animal- and FarmLevel Risk Factors

Abstract

An infection of the mammary gland causes damage to the udder tissue, affecting animal welfare and causing significant economic losses to the farmer. This cross-sectional study investigates the incidence, prevalence, and risk factors of clinical mastitis in meat-producing sheep flocks during the 2025 lambing season in the Netherlands. A questionnaire was completed on 22 farms in the Netherlands and udder examinations and body condition scoring (BCS) was conducted in 390 ewes. Univariable and multivariable analyses identified early supplementation of concentrates before lambing, feeding unfertilized silage and a higher culling rate to be associated with a higher incidence of mastitis reported by the farmer. This findings suggest that current feeding practices during late pregnancy may influence mastitis risk. No significant associations were found between animal-level risk factors and the incidence of mastitis reported by the farmer in the lambing season of 2025. The mean incidence of clinical mastitis reported by farmers in the lambing season of 2025 was 7.4 cases per 100 ewes per year. The observed prevalence based on visual and palpable udder abnormalities was 26.7%. More than half of the mastitis cases detected during the study were not known by the farmer, indicating potential gaps in mastitis detection. A plausible explanation for this notable gap is insufficient monitoring, as 95.5% of the participating farmers reported checking udders for abnormalities only immediately after lambing and before mating. As these are the only check moments, any new infections that develop in between without visible behavioural change in the ewe or lambs can be missed.