Abstract

Depot leuprolide acetate is widely used to control avian reproduction, despite variable results. Treatment schedules are still empirical and vary widely. Furthermore, no information is available on differences in sensitivity between avian species or timing of treatment during the breeding cycle. The objective of this study is to investigate the effect of leuprolide acetate on egg production and fertility, semen quality, and circulating reproductive hormones in two duck species (mallard and black duck). In a pilot study, two male (one mallard, one black duck) and two female (one mallard, one black duck) ducks were injected with 2 mg/kg Lupron® (TAP Pharmaceuticals, Inc., Deerfield, IL) intramuscularly. Ducks were housed in pairs and had produced two clutches of eggs that were removed before study onset. Three blood samples were collected daily before treatment, and blood sampling continued weekly for 5 weeks following treatment. Egg production recommenced 8 days after treatment in the female black duck and 6 days after treatment in the female mallard. All six black duck eggs were infertile; however, this pair had demonstrated similar low fertility in previous clutches. All eight mallard eggs were fertile. Following treatment, no decrease in plasma LH concentrations was measured in the male ducks. Plasma testosterone concentrations measured 1 hr after treatment increased substantially (black duck, ~3-fold; mallard, ~45-fold) in both males, which persisted throughout following blood sampling 1 wk later (black duck, ~2.5-fold; mallard, ~11-fold). In the females, circulating LH, PdG, E1-glucuronide, and testosterone concentrations did not decrease after Lupron® injection. However, 2 weeks after treatment, plasma LH concentrations declined in both females, and steroid hormones decreased in the female mallard, most likely coinciding with end of egg production and onset of incubation, rather than a suppressive effect of Lupron®. These results indicate that following Lupron® treatment, male and female mallard and black ducks continued to show reproductive behaviors including pair-bonding, copulation and egg-laying, resulting in fertilized eggs for the mallards. Additional experiments (including semen evaluation) are ongoing with 28 pairs of mallard and black ducks. In conclusion, preliminary data reveal that a single injection of 2 mg/kg leuprolide acetate administered during the breeding season does not suppress reproductive function in male and female mallard and black ducks.