Growth modeling of pasture or confinement-raised broiler chickens

Abstract

Objective: To evaluate the growth of pasture or confinement-raised broiler chickens, using the Gompertz, Logistic and Richards models, and identify the most appropriate.

Methodology: One hundred ten straight-run broilers Ross 308 were distributed in two systems: pasture or confinement. Birds were weighed every week until 56 d of age. Three growth models (Gompertz, Logistic and Richards) were considered and compared based on three goodness of fit criteria (coefficient of determination, Akaike information criterion and Bayesian information criterion).

Results: The initial (L) and exponential (K) growth rates of the Gompertz and Logistic models, respectively, were higher in confined birds (L = 0.1232, K = 0.0779) compared to those raised in pasture (L = 0.0944 , K = 0.0657). The maximum relative growth (K) of the Richards model was lower in chickens in confinement (0.0129) than in pasture system (0.0153). With the three models, higher asymptotic weights (WA) were estimated for confined chickens (3,967.1 to 9,095.5) compared to pasture birds (2,461.7 to 5,192.6). According to the criteria considered, the Richards model had the best fit.

Implications of study: The results are only valid for straight-run Ross 308 broiler chickens and under the specified management conditions.

Findings: The growth of pasture or confinement-raised broiler chickens can be described with the Gompertz, Logistic and Richards models, however, the latter has a better fit.