5 YEARS STUDIES ON THE CONVERSION TO ECOL OGICAL MILK-PRODUCTION .1. PRODUCTION TECHNIQUES

On the experimental farm Schaedtbek a dairy herd of 60 cows was splitt ed into two equal groups beginning lst May, 1987. One group was manage d according to the rules of ecological farming, the other group in con ventional management was serving as control. From 1987 to 1992 164 lac tation records in ecological and 151 records in conventional milk prod uction could be evaluated. On farm land managed ecologically the phosp horus content of the soil decreased by 39 per cent in 5 years, the pot assium was reduced by 25 per cent and magnesium by 6 per cent. In ecol ogical fodder production grass-clover proved to be distinctively stabl e in yield, in total, however, 0,20 more hectares main fodder acreage per cow (= + 34 per cent) was needed than in conventional farming due to lower yields in total plant silage and 44 % points more milk produc tion from forage. Regarding nutrient contents and contaminants in feed there were no significant differences. The 305-days-records of dairy cows managed ecologically were 871 kg milk, 0,06 % fat and 0,16 % prot ein lower than those of cows managed conventionally. Comparing of 4 pa irs of monozygous twins there was no indication for genotype-environme nt interactions. Restricting concentrate feeding to 3 kg and 5 kg per day during the first 100 days in first and later lactations resp. prov oked an energy deficit, which resulted in elevated acetone values in m ilk but not in more incidences of metabolic disorders. The economic re sults showed slightly less feed costs per kg milk produced ecologicall y and 12 and 33 per cent less marginal profit per cow and area of fodd er production resp. which must be compensated by higher milk prices un der practical conditions.