Presence of Cathelicidin-1 in Milk as an Indicator of the Severity of Mammary Infection in Ewes

Aims: The importance of cathelicidin-1 as an indicator of the severity of mammary infection in ewes. Background: Mastitis is an important disease of sheep, affecting their health and welfare. Objective: The association of the presence of cathelicidin-1 in milk samples from ewes with mastitis with the severity of the infection. Methods: Ewes were intramammarily inoculated with Mannheimia haemolytica or Staphylococcus chromogenes. Conventional (clinical, bacteriological and cytological examinations; milk yield measurements) and proteomics evaluation (2-DE, MALDI-TOF MS) to record cathelicidin-1 spot optical densities in milk samples were recorded. Results: Ewes challenged with M. haemolytica developed clinical and ewes challenged with S. chromogenes subclinical mastitis (P=0.05). The challenged organism was isolated from milk samples from inoculated mammary glands; increased somatic cell counts were also recorded. Cathelicidin- 1 was detected in milk samples from the inoculated side of udders of all ewes. Mean spot density of cathelicidin-1 from samples from inoculated glands of ewes challenged with M. haemolytica was higher than from ewes challenged with S. chromogenes: 2896 ± 973 versus 1312 ± 361 (P =0.034). There were significant correlations between the presence of clinical mastitis / somatic cell counts with the spot density of cathelicidin-1 on 2-DE gels (P=0.043 and P=0.023, respectively). There was also a significant inverse correlation between the mean spot densities of cathelicidin-1 in milk samples and the milk yield of respective ewes on D10 (P =0.031). Conclusion: Potentially, cathelicidin-1 could be used as a marker to indicate the severity of damage to the mammary parenchyma.