Predicting effective caloric value of nonnutritive factors: III. Feed form affects broiler performance by modifying...

Two trials of an experiment were conducted to confirm the relationships among effective caloric value (ECV) of the diet, net energy for gain (NEg), BW, feed conversion ratio (FCR), and broiler behavior. Further, we sought to examine such factors with benefits of pelleting, including feed form history (pellets vs. mash) in females from 2 strains of commercial broilers. Composition of gain was measured on a sample of birds in both trials. In trial 1 birds were reared to 23 d on feed in crumble form, when the birds were provided a feed in pellet or mash form for 7 d. Pelleting the feed increased ECV and total NEg, while decreasing eating and increasing resting behavior. Significant correlations (P < 0.05) among resting, NEg, and ECV occurred. In trial 2, birds were reared to 23 d on a crumble diet and then fed diet in mash or pellet form to 36 d. At 37 d of age, half of the birds from each strain and feed form history combination were switched to the alternative feed form. Interactions of strain by grower feed form were present for BW, initial fat, and body energy content indicating that pelleted feed was required for optimum broiler performance of 1 strain. Grower feed form by finisher feed form interactions were present and demonstrated that birds switched from pellets or mash to the alternate feed form consumed more feed in less time than birds that remained on their previous feed form. Significant correlations were observed in both trials between behaviors and FCR and ECV, whereas NEg reflected these differences in trial 1 but not trial 2. Regression analysis indicated that FCR and subsequently ECV were best predicted by lean gain, whereas NEg was best predicted by fat gain. Further, regression analysis established interactive equations in which ECV was predicted (R2 > 0.99) by eating and resting behavior. The results of these trials indicate that the effects of feed form are caused by a modification of behavior patterns, that ECV is responsive to such behavior changes, and that ECV is an effective estimator of the relative caloric value of genetic, management, and husbandry influences.