Molecular screening of ovine mastitis in different breeds

Abstract

Clinical and subclinical mastitis directly affect mammary gland function and have a great economic impact on the sheep and goat dairy industries. The present study explores molecular diagnosis of ovine subclinical mastitis as a faster and more precise screening method compared with microbiology and biochemical techniques to assess the molecular and chemical properties of raw milk samples from healthy animals from 3 breeds of sheep raised in Portugal. Based on 16S ribosomal RNA screening by PCR, milk samples from all sheep were categorized as contaminated (n = 123) or noncontaminated (n = 104). For contaminated milk, different specific primers were used for pathogen identification (Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, and Streptococcus uberis). Streptococcus agalactiae was identified as the most frequent agent. We further assessed whether contaminated versus noncontaminated samples were chemically different in terms of fat, protein, lactose, pH, and solids-not-fat. This molecular screening method allowed rapid and efficient identification of contaminated raw sheep milk, including pathogen identification, before significant alterations in milk chemical properties could be detected. This methodology may lead to a specific and efficient animal treatment and consequently less expensive flock management.