A comparison of production and management between Wisconsin organic and conventional dairy herds

Abstract

An observational study was conducted in Wisconsin to compare production and management on organic and conventional dairy farms. Thirty organic dairy herds, where antimicrobials are rarely used for calves and never used for cows, were compared with 30 neighboring conventional dairy farms on which antimicrobials were routinely used for animals of all ages. A seven-page questionnaire regarding milk production, milking practices, housing, incidence of the major dairy diseases and medical treatments was used to assess management and production during 2000–2001. Body condition scores (BCS) of lactating cows and environmental and animal sanitation scores (EASS) were also collected on each of two occasions. The organic herds had significantly fewer cattle than did the conventional herds ( P=0.017). The average daily milk production per cow in organic dairy herds (20.2 kg/day) was lower than that of conventional herds (23.7 kg/day). The incidence of clinical mastitis (CM) on organic farms (28 cases per 100 cow-years at risk) was not statistically different from that of on conventional farms (32 cases per 100 cow-years at risk). No significant difference in bulk tank somatic cell count (BTSCC) was observed between organic farms (262,000 cells/ml) and conventional farms (285,000 cells/ml). The average annual cull rate was 18.0 cases per 100 cow-years for the conventional farms and 17.2 for the organic farms ( P=0.426). Our paired t-test results indicated significantly higher parasite burden on organic dairy farms; however, no significant difference between the two farm types when controlling for season (March and September), grazing intensity (no grazing, little grazing, grazing with access to housing and grazing only) and herd average milk production per cow. There was little evidence of other fundamental differences between the two farm types in other management and production parameters.