Disappearance of signs of heat and induction of ovulation in oestrous queens with gonadorelin: a clinical study

Objectives: The objective of this study was to assess the efficacy of a single intramuscular administration of gonadorelin to induce ovulation in queens in oestrus. Methods: Twenty-seven queens presented in oestrus for elective ovariectomy were divided into a treatment (n = 19) and a placebo (n = 8) group. Treated queens received a 50 µg dose of gonadorelin, while placebo-treated queens were injected intramuscularly (IM) with an equal amount of saline solution. All treatments were performed between the second and fourth days of heat. Results: Two days later, signs of behavioural heat had disappeared in all gonadorelin-treated queens, while 5/8 placebo-treated queens were still in heat. Following ovariectomy, performed 4 days after drug administration, the ovaries of each queen were evaluated histologically and the number of corpora lutea were counted. Sixteen of 19 (84%) gonadorelin-treated queens had ovulated and developed five (range 2–9) corpora lutea, while 3/8 (37%) placebo-treated queens had ovulated and developed five (range 3–6) corpora lutea. Conclusions and relevance: This is the first study to document the efficacy of a 50 µg/cat gonadorelin dose to induce ovulation in oestrous queens when administered IM on days 2–4 following the onset of oestrus.