Treatment of cystic ovarian disease in dairy cows with gonadotrophin-releasing hormone: a field study.

In a field trial in the Netherlands 765 dairy cows were treated during 869 lactations with 500 micrograms gonadotrophin-releasing hormone (gonadorelin i.m.) for cystic ovarian disease (COD) between June 1987 and April 1996. COD was defined as the presence of a large follicle (> 2.5 cm) on one or both of the ovaries in the absence of a corpus luteum. Two treatment groups were formed, based on the interval from parturition to first treatment, with day 60 being the cut-off between groups 1 and 2. The aim of this study is to examine whether there is a relationship between the moment of diagnosis and treatment (before or after day 60 post partum) and its result. In group 1 90.0% of first treatments were effective and in group 2 93.3% (p = 0.08). This was reflected by the slightly higher number of treatments needed for animals in group 1 (1.11 versus 1.07, p = 0.08). The efficacy rate after one treatment did not significantly differ between the groups (1.63 versus 1.69, p = 0.40) and nor did the interval between 1st insemination after treatment and conception (p < 0.63). In conclusion, it can be stated that gonadorelin is effective as therapy irrespective of the timing of diagnosis and treatment.