Diagnosis and threshold values of subclinical mastitis in goats

This paper reports threshold values of leucocyte count, lactose and chloride contents in relation to California mastitis test (CMT) of milk samples of mastitic and non-mastitic goats. CMT, leucocyte count, lactose and chloride contents of milk were analysed in 204 caprine milk samples collected 4–8 weeks post-parturition. A milk sample was considered mastitic when it had a CMT score of ≥ 1 + in association with threshold values of two of three parameters: leucocyte count (≥ 0.63 millions/ml), lactose ( ⩽ 4.33%) and chloride contents (≥ 0.109%). Leucocyte counts with nil, trace and 1 + CMT reaction, respectively, varied from 0.07–0.81 (mean 0.279 ± 0.013), 0.09–0.81 (mean 0.417 ± 0.039) and 0.31–2.13 (mean 0.812±0.054) million/ml. Lactose contents with nil and trace CMT reaction, respectively, varied from 4.18–5.59% (mean 4.73±0.35) and 4.06–4.78% (mean 4.52±0.089). Chloride contents with nil and trace CMT reaction, respectively, varied from 0.065–0.130% (mean 0.103±0.001) and 0.035–0.115% (mean 0.103±0.003). From 67 milk samples with nil and trace CMT reaction, 26.9% had Micrococcus sp., Staphylococcus aureus, Citrobacter and Escherichia coli which showed that mere isolation of bacteria was not sufficient to incriminate with mastitis unless the milk also had inflammatory parameters. Validity of different tests in relation to CMT showed that false % was lowest for leucocyte count (7.l), followed by lactose contents (11.8 ), suggesting that these tests had better predictive values than chloride contents. The best correlation was between CMT and leucocyte count, followed by CMT and lactose content. The results indicated that lactose test could be a useful, quick and readily available tool for routine checking of udder health under Indian rural conditions.