The Impacts of Female Access during Rearing on the Reproductive Behavior and Physiology of Pekin Drakes, and Flock Fertility

Abstract

Commercially housed Pekin ducks (Anas platyrhynchos) are typically reared in same sex groups to facilitate separate diet provisioning. Several female ducklings are sometimes mixed into the otherwise all-male pens. This practice is thought to increase flock reproductive success. To evaluate this hypothesis, we reared ducklings in alternating same-sex groups (150 hens or 30 drakes/pen; 8 groups/sex) and evaluated the impacts of rearing on drake mounting behavior, testosterone levels, and flock fertility. At 12 days, three females were placed into four of the male duckling pens. At 20-22 weeks of age, adjacent male and female pens were moved into pens within a breeder barn, and combined to form mixed-sex pens. The number of correctly aligned mounts performed by 10 focal drakes per pen was evaluated over 3 days (12 h/day) at 26, 32, and 45 weeks of age. Circulating testosterone concentrations were analyzed from blood plasma samples collected from the focal drakes at 15 (baseline), 22, 28, 34 and 45 weeks of age. Pen-level fertility was determined at 33-34 and 45-46 weeks of age. Mount and testosterone data were analyzed using a Generalized Linear Mixed Model and a Linear Mixed Model in R 4.0.5, with duck in pen as a random effect. A Linear Mixed Model was used to analyze fertility data, with pen as a random effect. None of the measured variables were impacted by rearing treatment, but all varied with flock age. Physical access to female ducklings during rearing did not enhance flock reproductive success.

Keywords: Pekin duck; behavior; fertility; physiology; reproduction; testosterone.

Figure 1

A marked focal Pekin drake performs a correctly oriented mount on top of a hen. The orientation is head-to-head and tail-to-tail.

Figure 2

Average number of correctly oriented mounts for Pekin drakes over three 12 h observation periods at 26, 32, and 45 weeks of age for same sex rearing groups and mixed sex rearing groups. Mount rate values differed by age (p < 0.001) but not treatment. Mount rate values are presented as estimated marginal means and standard errors.

Figure 3

Number of correctly oriented mounts for individual Pekin drakes over three 12 h observation periods at 16, 32, and 45 weeks of age.

Figure 4

Circulating average testosterone concentrations in drake Pekin ducks from same sex rearing groups and mixed sex rearing groups from 15 to 45 weeks of age. Testosterone levels differed by age (p < 0.001) but not treatment. Testosterone concentration values are back-transformed from a logarithmic transformation and presented as estimated marginal means and standard errors.

Figure 5

Average fertility percentages calculated based on pen-level data collected when ducks were 33 and 34, and 45 and 46 week of age. Average flock fertility differed by age (p < 0.001), but not treatment. Fertility values are back-transformed from a logarithmic transformation and presented as estimated marginal means and standard errors. Fertility was determined based on candling of eggs.