Abstract:

The study was conducted to evaluate the performance of California mastitis test, electrical conductivity measurement and lactose content as markers for subclinical-intramammary infection (IMI) in goats. It was performed at Humeimeh research station for Damascus goats, General commission for scientific agricultural research (GCSAR) from February to march 2011 and done on dairy goats aged 2 to 6 years. Milk samples were taken from 134 dairy goats during morning milking according to habitual procedure and screened for evidence of subclinical mastitis by California Mastitis Test (CMT), electrical conductivity measurement (EC) and lactose content (LC) of milk. Positive (+1 to +3) CMT and/or high electrical conductivity milk samples were subjected to bacteriological examination to distinguish between healthy (absence of mastitis agents) and infected (presence of contagious or environmental mastitis agents). The overall prevalence of subclinical mastitis was found to be 24.6%. Percentage of positive (+1 to +3), suspected and negative CMT reactions were 76.85, 8.95 and 14.2%, respectively. The values of electrical conductivity for negative, suspected and positive (+1, +2 and +3) CMT milk samples were 3.93 ± 0.64, 4.47 ± 0.61, 4.68 ± 0.72, 4.81 ± 0.76 and 6.56 ± 0.85 ms/cm, respectively. T-test has been shown statistical differences in California mastitis test reactions and electrical conductivity readings, and not statistically for milk lactose content, between positive and negative results for bacterial growth. Intramammary infection was found in 40.9% milk samples caused by Staphylococcus (75%), alone E. coli (16.6%) or associated with streptococci (8.3%). Correlation coefficient between CMT reactions with electrical conductivity readings was R = 0.494. Higher coefficient correlation for electrical conductivity measurement and Kappa agreement index (R = 0.491 and 0.42 respectively) with positive bacterial growth milk samples than for CMT (R = 0.35 and 0.12 respectively) make the electrical conductivity measurement more compatible with the results of bacteriological analysis than CMT despite a slight increase of CMT sensitivity, and reduced number of real negative cases.

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