P2.146 Thursday, Jan. 5 Sequence position, but not age, significantly influences sex ratios in the domestic chicken PINSON, SE*; NAVARA, KJ; University of Georgia; University of Georgia firstname.lastname@example.org
Birds have demonstrated a remarkable ability to bias sex ratios prior to hatch in relation to a variety of social and environmental conditions. Several studies have found relationships between age or sequence position and biased sex ratios in wild and captive bird populations. There is little information with regards to the influence of these factors on sex ratios of domestic chickens, which are often used as the study species in experimental sex ratio studies. The purpose of this study was to determine if there is variation between the proportion of males produced at different ages or sequence positions in commercially available birds. We collected fertile eggs from randomly selected hens when they were 32, 35, 53, 56, 59, and 63 weeks of age. We also collected fertile eggs from randomly selected hens and assigned the appropriate sequence position to each egg. We incubated the eggs for 8 days and quantified the sexes using a molecular sexing technique. In our study, laying hens produced statistically similar proportions of males for all sampled weeks of age, so age does not appear to be a factor influencing primary sex ratios in chickens; however, there was significant variation between sequence positions. A significantly greater proportion of male offspring was produced from the third egg in the sequence compared to the earlier (χ2=5.085, p=0.02) and later (χ2=3.734, p=0.05) sequence positions. Results of this study suggest that sequence position can influence sex ratios in hens, so it is a factor that should be considered when designing and executing manipulative sex ratio studies in domestic chickens.