Effect of intramammary infection by Staphylococcus caprae on somatic cell counts and milk composition in goats

Abstract

Since its identification by Devirese et al. (1983), Staphylococcus caprae has been frequently isolated from udder halves of goats with subclinical intramammary infection (IMI) (Contreras et al. 1995; Poutrel et al. 1996). Several different studies have demonstrated the capacity of Staph. caprae to persist throughout lactation (Poutrel et al. 1996; Contreras et al. 1997; Bedidi-Madani et al. 1998a) and during the dry period (Poutrel, 1984). Bedidi-Madani et al. (1998a) found that isolates of Staph. caprae from udders of uninfected goats express potential virulence factors (different exoproteins and slime); other researchers have occasionally isolated it from clinical cases of goat mastitis (Deinhofer & Pernthaner, 1995), or from human clinical specimens associated with bone and joint infection (Vandenesh et al. 1995; Shuttleworth et al. 1997). In spite of these forms of pathogenicity, some studies have not shown significant increases in somatic cell count (SCC) of milk from goat udder halves infected by Staph. caprae (Deinhofer & Pernthaner, 1995; Poutrel et al. 1996). Moreover, there is a lack of information on the effect of infection by this mammary pathogen on milk yield and composition. Knowledge of repercussions for hygiene and production would be useful in mastitis control programmes in view of the high frequency of isolation (higher than 22% of the staphylococci isolated) of Staph. caprae in dairy goat herds (Contreras et al. 1995; Poutrel et al. 1996). The aim of the present investigation was to ascertain the significance of persistent subclinical IMI by Staph. caprae on SCC, milk yield and physical-chemical parameters of Murciano-Granadina goat milk at mid-lactation.