Somatic cell count, lactoferrin and NAGase activity in milk of infected and non-infected udder halves of dairy goats.

摘要

Based on a repeated sampling the influence of an intramammary infection on the somatic cell count (SCC), the content of lactoferrin (Lf) and the activity of N-acetyl- beta -D-glucosaminidase (NAGase) in goats' milk was investigated. 58 dairy goats (German Improved Fawn) were sampled weekly over 3 consecutive weeks and the udder halves were classified according to the results of the bacteriological analysis of the foremilk samples and the results of their parallel half into three groups: uninfected halves with an uninfected parallel half (NoInf/NoInf), uninfected halves with an infected parallel half (NoInf/Inf) and infected halves with an uninfected parallel half (Inf/NoInf). None of the goats had two infected halves, thus, this group was omitted. 15 out of the 58 goats were infected on one udder half. The bacteria detected were Staphylococcus aureus (n=4), coagulase-negative staphylococci (n=7), corynebacteria (n=3) and esculin-positive streptococci (n=1). Log₁₀ SCC, log₁₀ Lf and log₁₀ NAGase were strongly correlated to each other and changed over the sampling period but not uniformly, revealing a significant effect of the sampling day on the variables (F_6,98=29.13, p<.001). This could not be explained by an underlying effect due to the stage of lactation or the estrus season the animals were in, and therefore needs further investigation. The infection status had a significant effect on log₁₀ SCC (F_2,103=20.22, p< .001), log₁₀ Lf (F_2,103=11.18, p<.001) and log₁₀ NAGase (F_2,103=12.06, p<.001). Inf/NoInf differed significantly from NoInf/NoInf as well as NoInf/Inf for log₁₀ SCC (p<.01) and log₁₀ Lf (p<.001) whereas the NoInf/NoInf did not differ from NoInf/Inf indicating that the infected halves did not influence their uninfected parallel half. For log₁₀ NAGase this was different: infected halves differed significantly from NoInf/NoInf (p<.01) but not from NoInf/Inf which might be caused by a dependency of the udder halves. Results support the approach to monitor mastitis in goats by means of Lf or NAGase instead of SCC. Further studies should explore the effect of other independent variables, such as estrus, on these indicators and aim for thresholds indicating an intramammary infection.