Comparing irrigated biodynamic and conventionally managed dairy farms. 2. Milk production and composition and animal health

Ten paired irrigated dairy farms under biodynamic (BD) and conventional (CV) management were compared over a 3-year period (1991-93). The paired farms were located in the irrigation districts of northern Victoria and southern New South Wales and were matched for soil type, cattle breed and farm area. The BD farms practised BD principles for an average of 16 years before the study. The effects of farm management on milk yields and composition and animal health were examined by annually surveying farm managers regarding disease incidence and chemical treatment of animals, and by measuring milk yield and composition and faecal egg counts over the experimental period. The two hypotheses tested were that (1) milk volume and milk solids per cow would be lower under BD management, and (2) the incidence of internal parasitic infection and disease would be lower under CV management. Milk production and milk components produced, both on a per hectare and per cow basis, were 24-36% higher (P < 0.01) under CV management, due to significantly higher pasture intakes (P < 0.001). Although the incidence of parasitic infection was similar for mature cows, CV farms consistently used a greater number of chemical treatments (P < 0.05). Although BD heifer calves <8 months in age had significantly (P < 0.05) higher faecal egg counts, the results highlight the risk of reduced growth rates in calves due to high rates of parasite infection, under both management systems. Somatic cell counts were higher (P < 0.05) under BD management, with this being consistent with the use of significantly less chemical treatments under this management system. The implications of these findings for both CV and BD management for milk production and animal health are discussed. © CSIRO 2007.