Effect of the Prolactin Inhibitor Cabergoline and the Gonadotropin Releasing-Hormone Agonist Deslorelin in the Suppression of Plasma Prolactin Concentrations and Egg Laying in Quail (Coturnix japonica)

Abstract

Egg binding and excessive laying frequently affect avian patients, and in many cases the treatment includes suppression of egg production. Currently, for the suppression of egg production in avian patients, a gonadotropin-releasing hormone agonist, in the form of a deslorelin implant, is often used. However, the commercially available deslorelin implants have an undesired delayed onset, as well as a potential brief increase in gonadotropin secretion after administration ("flare-up" effect) that can lead to oviposition before the actual suppression of gonadotropins. The objective of this study was to investigate whether the prolactin inhibitor cabergoline suppresses ovulation and whether it could be used to bridge the time until the onset of effect by the deslorelin implant. We measured the effect of cabergoline (30 µg/kg PO q24h × 14 days), deslorelin implants (4.7 mg SC), and a combination of both on egg laying and plasma prolactin concentrations in 37 quail (Coturnix japonica) over 6 weeks. Quail were divided into 4 groups: group DesCab (deslorelin implant and cabergoline oral; n = 9); group DesPlac (deslorelin implant and placebo oral; n = 9); group PlacCab (placebo implant and cabergoline oral; n = 9); and group PlacPlac (placebo implant and placebo oral; n = 10). Regular egg laying stopped in 100% (9/9) of birds in group DesCab and 78% (7/ 9) of birds in group DesPlac within 5 days of placing the deslorelin implant. No bird ceased egg production in group PlacCab (0/9), and 10% of birds ceased egg production intermittently in group PlacPlac (1/10). Treatment with the deslorelin implant (P < .001) and with cabergoline (P = .04) had a significant (negative) influence on plasma prolactin concentrations compared with the baseline. The interaction of deslorelin and cabergoline treatment, as well as time after initiation of treatment, did not have a significant effect on plasma prolactin concentrations. These results show that daily oral cabergoline has no significant influence on egg laying and only a minor biologically nonsignificant effect on lowering the relative plasma prolactin concentrations in quail.