Location: Animal Biosciences & Biotechnology Laboratory
Project Number: 8042-31000-111-006-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2023
End Date: Jul 31, 2025
Objective:
Within the broiler breeder industry, feed restriction regimens are necessary to ensure sufficient reproductive capabilities. However, the long term interplay between early life metabolic shifts and reproductive capabilities during the laying cycle is poorly understood. The goal of this study is to assess how the feeding regimen during broiler breeder rearing can directly influence the underlying reproductive mechanisms and the condition of the gonads during sexual maturation and the breeding cycle. Further, this research will determine if different feed restriction regimens in females and males can provide reproductive advantages during the breeding cycle. The proposed work will determine the impact of feed restriction regimens on ovarian and testes parameters, fertility rates, hatchability rates, circulating hormone profiles, and fat pad steroid hormone signaling.
Approach:
Females and males will be separate sex reared. At 4 weeks of age (woa), chicks will be randomly assigned to one of two feeding programs: (1) 5-2: two non-consecutive ‘off’ feed days per week, with the 7 days of daily allocations dispersed over 5 days; or (2) SKIP: Skip-a-day feed allocation, with birds receiving double their daily allocation every other day. Body weights will be recorded to maintain birds at target weight. During the laying cycle, hens will undergo artificial insemination using pooled screened semen (1:10 male-to-female ratio) to remove the confounding impact of natural breeding. Eggs will be collected and set to assess true fertility, hatchability, and chick quality throughout lay. The breeding pairs will consist of four treatments, referring to the pullet/cockerel feeding regimen: 1. 5-2 female + 5-2 male 2. 5-2 female + SKIP male 3. SKIP female + 5-2 male 4. SKIP female + SKIP male, to determine if there is a reproductive advantage to utilizing different feed restriction regimens in males and females. In addition to egg production, fertility and hatchability measurements throughout the laying cycle, a subset of females will be sampled at 12, 22, 23, 30, and 50 woa representing an immature baseline, post-photostimulation, initiation of egg production, peak fertility, and declined fertility time points, respectively (n=5). At each time point, the following will be collected: (1) blood samples to assess estradiol and progesterone circulating concentrations through radioimmunoassays, (2) ovarian samples for follicle parameter measurements and histology, (3) fat pad samples to determine estrogen and progesterone receptor levels through western blotting, and (4) sperm storage tubules to determine the percentage of sperm storage tubules filled. Similarly, a subset of males will be sampled at 12, 22, 26, 35, and 55 woa representing an immature baseline, post-photostimulation, initiation of semen production, peak fertility, and declined fertility time points, respectively. At each time point, the following will be collected: (1) blood samples to assess testosterone and dehydroepiandrosterone-sulfate circulating concentrations through radioimmunoassays, (2) testes samples for testicular weight measurements and histology, (3) fat pad samples to determine androgen receptor levels through western blotting, and (4) semen samples to determine sperm concentration, morphology, and mobility.
