Abstract
Three experiments were conducted to determine quadratic growth functions based on cumulative protein and energy intake in broiler chickens during starter, grower, and finisher phases of feeding. Indian River male broiler chicks were used for all experiments. In experiment 1, a 4 x 4 factorial design was utilized consisting of 4 levels of dietary protein (16, 20, 24 and 28%) and 4 levels of dietary energy (2970, 3120, 3265 and 3410 kcal ME/kg). These diets were replicated twice and fed to 40 birds/pen for 21 days. The quadratic growth function best describing growth during the starter phase was: BW = 38.28013 + .62604*P + .172768 *E - .009532*P^2 - . 000047201*E^2 + .001238*P*E, where BW = grams body weight; P = grams cumulative protein consumption; and E = Kcal cumulative energy consumption. In experiment 2, three economical starter diets selected from experiment 1 were fed for 21 days after which nine diets in a 3 x 3 factorial arrangement (16, 20 and 24% protein and 3120, 3265 and 3410 kcal ME/kg) were fed for another 21 days. The grower diets were thus replicated 3 times. The quadratic growth function best describing growth through the grower phase was BW = 36.068398 + 1.727053*P + .103206*E - .000072981*P^2 + .000001109*E^2 - .000092706*P*E. This quadratic growth function was not suitable for use in a least cost quadratic programming model because of the positive coefficient describing the quadratic effects of cumulative calorie intake. In experiment 3, nine pens were allocated to each of three economical starter and grower diets selected from the previous two experiments. These diets were fed for 42 days after which finisher diets consisting of 16, 20 and 24% protein and 3120, 3265 and 3410 kcal ME/kg were fed for another 14 days in a 3 x 3 factorial design. The quadratic growth function best describing growth through the finisher phase was BW = 55.447192 + 1.265325*P + .107697*E - .001466*P^2 - .000007127*E^2 + .000165*P*E. This quadratic function accurately predicts growth throughout 8 weeks of broiler production and appears suitable for use in a least cost quadratic programming model.
Obunike, Joseph Chukwunyelu (1990). The quadratic effects of energy and protein in phase fed broilers. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1190527.