Effects of milking frequency on goat immune status

Abstract

The aim of present study was to identify the effect of milking frequency on immune status of dairy goats. Eleven dairy Majorera goats in the middle lactation were milked during 5 weeks at different milking frequencies. The first and fifth week, goats were milked once a day (09:00), the second and fourth week goats were milked twice a day (09:00, 17:00), and the third week goats were milked three times a day (09:00, 13:00, 19:00). Blood samples were taken once a week each Wednesday. White blood cells count (WBCC) was measured and, after that, blood was centrifuged and the plasma fraction storage at -80°C until subsequent analysis. IgG, IgM and complement system activity (Classical plus alternative and alternative pathway alone) were evaluated. A Proc Mixed procedure was performed by SAS statistic package. Mean blood plasma IgG was 26.7, 17.8, 9.8, 11.7 and 14.8 mg/ml at week 1, 2, 3, 4 and 5 respectively. Blood plasma IgG was significantly higher at week 1 than other periods studied and the level of IgG was reduced as milking frequency was high. Blood plasma IgM was 0.8, 0.9, 1.0, 1.1 and 1.3 mg/ml at week 1, 2, 3, 4 and 5 respectively. The highest blood plasma IgM was observed at week 5, showing an increase trend during the experimental time. WBCC was 14.0, 14.0, 15.0, 13.9 and 13.5x103 cells/ml at week 1, 2, 3, 4 and 5 respectively. WBCC at week 3 was significantly higher than at week 5, although a trend was observed while milking frequency increased the WBCC concomitant increased. Complement system activity measured as Classical plus alternative pathways activation was 44.7, 47.0, 55.2, 71.7 and 71.7 % at week 1, 2, 3, 4 and 5 respectively. Complement activity measured as alternative pathway alone was 28.8, 31.8, 39.2, 42.0 and 40.9 % at week 1, 2, 3, 4 and 5 respectively. Complement activity measured as classical plus alternative pathways and alternative pathway alone were affected (increasing) by milking frequency during the first three weeks, and after that the complement activity still increased. As a preliminary conclusion, milking frequency affect in a different way the innate and acquired immune status of dairy goats. Nevertheless, further studies are necessary.