Intramammary infections in dairy goats: recent knowledge and indicators for detection of subclinical mastitis

Intramammary infections (IMI) in goats constitute an enormous animal health problem, alter milk composition, lower the hygienic value of milk, impair the processing properties of milk and cause high economical losses in dairy farming today. A great part of IMI in dairy goats can be assigned to the group of subclinical mastitis (SCM) with no outward clinical symptoms. Staphylococci are certainly the most common type of pathogens in goat milk, but the frequency of occurrence of this pathogenic group varies greatly. This review tries to summarise the most recent knowledge about IMI in dairy goats and possible parameters for detecting this disease with the main focus on SCM. The gold standard for mastitis detection is the determination of bacteriological status, but analysis is time-consuming, costly and not relevant for practical use. Suggestions have been made to use parameters like somatic cell count (SCC), the California-Mastitis-Test (CMT), electrical conductivity (EC), milk composition (fat, protein, lactose), N-acetyl-beta-D-glucosaminidase (NAGase), lactoferrin (Lf), beta-Glucuronidase and lactate dehydrogenase (LDH) alternatively. SCC, the most established parameter for the diagnosis of the udder health status in cows, seems to be no reliable parameter for the detection of SCM at the proposed static level of 1 10(6) cells ml(-1), which has been proposed by many authors. SCC in goats shows great variations (e.g., during lactation) and often higher numbers of > 1 10(6) cells ml(-1) without incidence of SCM were measured. SCC can increase solely due to physiological factors (like breed, parity, stage of lactation, estrus), hygienic standards and milking equipment. The impact of IMI on the parameters mentioned above, as well as the efficiency of diagnostic tools is discussed in this review.