Functional Analysis of Growth in Large White Male Turkeys

The Richards and Gompertz functions were used to analyze the growth curves of large white male turkeys. Gompertz function was yt=A*exp (-exp (b-kt)) where; yt is the body weight (g) at age t (weeks), A is asymptotic value and the both parameters b and k adjust slope and point of inflection. On the other hand, Richards function was yt=A*((1+b*exp (-kt)) ^ (-1/n)) where; n is shape parameter determining the position of the inflection point of the curve. The coordinates of the point of inflection are t+=b/k and y+=A/e (e= Eulerian number), t+= (-1/k)*ln│n/b│and y+=A/ for the Gompertz and Richards function, respectively. Body weights were recorded every week from 0 to 18 weeks of age. Data were individually taken from 24 males. Feed and water were supplied ad libitum. Floor space allowance was 0.50 cm2/bird during the study. The coefficient of determination (R2), weight (y+), age (t+) at the inflection point, the ratio of inflection/asymptotic weight (y+/A), degree of maturity (ut=yt/A) in 16th and 18th weeks were the same for both models and were 0.998, 5560 gram, 11.9 day, 0.368, 0.549 and 0.627, respectively.