A comparative study of reproductive performance in organic and conventional dairy husbandry

A comparative cohort study of reproductive performance in organic and conve ntional dairy husbandry was conducted using longitudinal data from the Norw egian National Board of Animal Production Recording from January 1, 1994 to December 31, 1996. The present study is the first study comparing reproduc tive efficiency in organic and conventional husbandry in which characterist ics such as herd size, breeding season, milk yield, parity, breed, use of a rtificial insemination (AI), and geographical distribution were taken into account. The organically managed cohort comprised 998 lactation periods, an d the conventionally managed cohort comprised 3016 lactation periods. Both groups were similar in herd size and geographical distribution. The followi ng reproduction variables were studied: days open, calving interval, calvin g to first AI interval, calving to last AI interval, and AI per cow. No con sistent difference in reproductive performance was found between the cohort s before adjustments were made for milk yield, breeding season, service, an d parity. After inclusion of these independent variables in the repeated me asures, mixed-model analyses, reproductive efficiency of organically manage d dairy cows was impaired compared with those under conventional management . In organic dairy farming, breeding efficiency was difficult to maintain i n cows bred during winter. Organic husbandry proved more efficient than did conventional husbandry in converting roughage into milk. Furthermore, the average multiparity percentage was higher in organically managed cows.