Analysis of poultry fertility data. 3. Analysis of the duration of fertility in naturally mating Japanese quail

The purpose of the present study was to test the appropriateness of iterative least squares regression for the evaluation of fertility data in naturally mating quail. In each of four trials, 20 male and 200 female randombred Japanese quail were housed in stacked breeder cages. Paired females were exposed to their assigned male for a single 48-h period. Eggs were collected for 2 wk following removal of the male, incubated, and fertility determined by visual inspection at egg breakout. In Trials 1 and 3, sexually experienced males were placed with experienced and inexperienced females, respectively. In Trials 2 and 4, inexperienced males were placed with experienced and inexperienced females, respectively. Duration of fertility, by male, was analyzed by iterative least squares, using the model y(x) = gamma/(1 + e beta(tau - x)) Overall fertility was analyzed with a log odds model following transformation to logits. Iterative least squares provided estimates of fertility duration of 3.75 to 9.18 d, with significant (P 0.05) differences in the duration of fertility observed between individual males as well as between the trials. Differences (P 0.05) in overall fertility (17.7 to 58.3%) were also observed, with inexperienced males paired with experienced females exhibiting the lowest overall means. Taken together, these results suggest that iterative least squares may be used to evaluate fertility in naturally mating populations and that reproductive experience can have a profound effect on the interpretation of fertility in naturally mating quail