Application of non-linear modelling to efficiency and nutrient partitioning in broilers and broiler breeders

Abstract

Nutritive values of feedstuffs used in broiler rations vary significantly. Corn and wheat are theprimary energy sources in many broiler diets, depending on geographical availability. As feed is a largeproportion of live production costs, broiler operations may decrease diet nutrient density to reduce overalldiet cost, however this reduction may have a negative impact on broiler performance and yield. The performance, yield, and allometric relationships were examined in broiler offspring from North American orEuropean male lines crossed with Ross 708 breeder females (NA x 708; EU x 708, respectively), and feddiets of differing dietary balanced protein (DBP) levels. Growth and performance were examined on corn-(Corn Experiment) and wheat (Wheat Experiment) based diets. It was thought the EU x 708 broilers wouldhave higher growth and yield performance on wheat-based diets compared to the NA x 708 broilers due toprimary cereal use during genetic selection. In each experiment, 1,600 broilers were allocated into 32 pensof 50 birds with 4 replicate pens per treatment. Part 1 of the thesis focused on the growth performance,yield, efficiency and allometric growth of the pectoralis muscles, drum + thigh, liver, heart, fat-pad, andsmall intestines of the broiler. Results indicated DBP and genetic strain were significantly interrelated onthe influence of growth and development of broilers.Part 2 of the thesis studied the energy partitioning of broiler breeder pullets reared in commercialsettings. Maintenance requirements are studied in broiler breeders due to the need for feed restriction tomaintain healthy body weight and reproductive performance of the flock. However, many studies have beenperformed in research settings which can not replicate industry conditions. Metabolizable energy of maintenance (MEm) was estimated utilizing data collected from 8,558 Ross 308 broiler breeders reared in floorhousing at two commercial breeder operations. MEm per metabolic body weight (BW/kg0.67) requirementswere lowest during periods of high feed restriction. Our estimation of maintenance was consistent withother studies under tightly regulated research settings.