Breeding for resistance to mastitis in United Kingdom sheep, a review and economic appraisal

Abstract

Mastitis is a problem in the sheep industry, and its incidence varies widely with how it is recorded, the breed of sheep and the farm. Virtually all the published information about the genetics of mastitis refers to dairy breeds of cattle and sheep, and there is little information for meat sheep breeds. Many dairy breeding programmes worldwide use the somatic cell count (scc) in milk as an indicator of resistance to clinical and subclinical mastitis, but it is difficult to measure in meat sheep breeds. Molecular genetic technologies may therefore be a more practical way to assess susceptibility to mastitis. This paper reviews the genetics of mastitis and considers the opportunities for breeding for resistance to mastitis, with particular reference to sheep. In addition, to investigate the potential economic effects of mastitis in a purebred sheep population, a computer model of flock dynamics was developed. By making a modest set of assumptions about the key farm parameters that influence lowland sheep production, the model showed that breeding for resistance (or other control methods), if it could reduce the risk of contracting mastitis by 10 per cent, would be worth pounds 8.40 per ewe, equivalent annually to pounds 2.7 million for the purebred sector of the Texel breed alone.

Comparison of bacteriological culture and PCR for detection of bacteria in ovine milk—Sheep are not small cows

“…Risks inherent in the use of antimicrobials in livestock production include the selection and dissemination of pathogens or commensals carrying antimicrobial resistance genes, which may subsequently affect human as well as animal health (Aarestrup et al, 2008). Alternative methods to reduce the incidence of mastitis in dairy as well as meat sheep include breeding for resistance and, experimentally, vaccination (Bergonier et al, 2003;Conington et al, 2008;Pérez et al, 2009). To select or develop targeted mastitis control measures, the causative agents of mastitis need to be known.…”

Global distribution and diversity of ovine-associated Staphylococcus aureus

“…Both clinical and subclinical intramammary infections reduce farm profitability, and impact on ewe health and welfare, and lamb growth rates. Mastitis has been estimated to cost £8.40 per ewe in the UK (Conington et al, 2008). With an estimated national flock of 14.8 million breeding ewes (EBLEX, 2012), this results in a potential cost to the UK sheep industry in excess of £120 M/annum.…”

Divergence of a strain of Pseudomonas aeruginosa during an outbreak of ovine mastitis

“…The economic losses due to mastitis are of major consequence for sheep farmers. In particular, mastitis can result in poor milk yields, changes in milk composition, premature culling of ewes and poor growth rates of lambs (Conington et al, 2008). Mastitis is frequently caused by the introduction and multiplication of pathogenic bacteria in the mammary glands.…”

“…Mastitis is an inflammation of the mammary gland and is a common condition in many sheep-rearing countries (Conington et al, 2008). The economic losses due to mastitis are of major consequence for sheep farmers.…”