A comparison of somatic cell count between organic and conventional dairy cow herds in West Germany stressing dry period related changes

Abstract

Mastitis is one of the major threats to animal health and thus to productivity in all dairy farming systems. Previous studies of organic dairy herds have indicated better udder health in organic herds, as compared to conventional herds but opposite results have also been reported. In view of the great implications that the dry period (DP) has on udder health, we aimed to compare milk performance data between organic and conventional dairy herds by specifically addressing the relation of somatic cell counts in milk (SCC) before and after the DP. On 68 farms (35 organic, 33 conventional) in Western Germany individual cow and herd production data were recorded next to data on SCC (herd, individual) between June 2002 and June 2004. For data analysis, SCC values > 150,000 cells/mL were defined as indicative for disorders of udder health. Milk yield per lactation ( Y) in organic herds amounted to 85% of the yields recorded for conventional herds; no differences were observed for herd size (HS) and age of cows ( A). For milk fat in bulk tank milk, no differences were established between the two management systems (MS); for milk protein there was a trend towards lower concentrations in milk from organic herds. The time course of SCC and of bacteria count in bulk tank milk was not different between organic and conventional herds. In organic herds, the portion of cows with individual SCC < 150,000 cells/mL in samples collected during the 3 months before and after the DP was lower ( P = 0.001) than in conventional herds. In addition, cows with individual SCC > 150,000 cells/mL during the 3 months preceding and following the DP were more frequent than in conventional herds. Following up the SCC of cows with either SCC below or above 150,000 cells/mL, the portion of cows in conventional herds that passed from elevated SCC before the DP to decreased SCC after the DP was higher ( P < 0.01) in conventional than in organic herds. For increasing SCC values above the 150,000 cell/mL threshold from drying-off to early lactation, there was a trend ( P = 0.07) for higher portions of cows in organic herds. These results should not be interpreted to simply reflect the use of antibiotic dry-cow therapy in conventional herds. However, they indicate that with the exception of synthetic antibiotics, all diagnostic measures and animal care at drying-off provide a means to improve mammary gland health regardless of the MS.