PERSISTENCE OF SUBCLINICAL INTRAMAMMARY PATHOGENS IN GOATS THROUGHOUTLACTATION

The goal of this study was to determine the persistence of caprine int ramammary pathogens throughout lactation and to detect the bias in dia gnoses when a single milk sample was used. We studied 131 goats throug hout 7 mo of lactation. Goats were sampled monthly, and 1834 milk samp les were bacteriologically analyzed. One hundred sixty-eight pathogens were isolated: 82.5% were micrococci, 9.5% were Gram-negative bacilli , and 8% were corynebacteria. An intramammary infection (IMI) was cons idered a true, persistent IMI when the same pathogen was isolated two or more times consecutively from the same half of the udder. One hundr ed one samples were considered to be truly positive, which produced pe rsistent IMI caused by nine different species (eight Staphylococcus sp p. and one Pseudomonas sp.). Statistical relationships were found betw een staphylococci and true-positive diagnosis and between corynebacter ia and false-positive diagnosis. No relationship involving Gram-negati ve bacilli was detected. A single milk sample had a positive predictiv e value (60%), high sensitivity (96.2%), high specificity (96.1%), and highly negative predictive value (99.8%).