A Model to Describe and Predict Post-Peak Changes in Broiler Hatchability

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Abstract
A model to accurately describe and predict hatchability is critical to management. Hatch records of 68 broiler breeder flocks, collected over 4 yr, were analyzed. The data were classified by grower, strain of chicken, ratio of male to females, season, and age. Flock hatchability met commercial expectations and statistically significant differences were attributed solely to age. Neither a strain × age interaction nor strain effect was detected. Hatchability increased rapidly until it reached a peak, and the post-peak decline was not uniform. Post-peak hatchability was best described by a seven-parameter segmented regression model. The three segments of the model consisted of the ascending slope (α), the gradually descending slope (β), and the rapidly descending slope (γ). The other parameters of the model were peak hatchability (Hp), age at peak (Ap), age at breakpoint (Ab) when the decline in post-peak hatchability abruptly shifted, and hatchability at breakpoint (Hb). The model may be used to evaluate the effect of diet and management, to predict hatchability, to assess economic longevity of a broiler breeder flock, and to plan replacement flocks.