EFFECT OF FREE-RANGE PRODUCTION SYSTEM ON BONE DEVELOPMENT, FOOT PAD HEALTH, WEIGHT OF BURSA OF FABRICIUS AND ADRENAL GLAND IN BROILERS
Abstract
Broilers are an important source of animal protein because of their fast growth rate. They are intensively produced under complete confinement, which makes them not express normal bird behaviour or exercise, thus interfering with their welfare. This study was designed to determine whether free-range production system in broiler birds would reduce stress, improve bone development, strengthen the immune system, and improve foot pad health when compared to those in complete confinement system. Four treatments were designed; Treatments A to C where the birds had free-range access at the age of 2, 3 and 4 weeks respectively and treatment D (control) where the birds were on complete confinement throughout. Newcastle vaccine was administered at weeks 2 and 4. Tibia bone ash weight was measured and expressed as a percentage of the weight of the bone. Relative weights of adrenal gland and bursa of Fabricius were used to compare degrees of stress and immune response between treatments respectively. Adrenal gland to the body weight ratio, bursa of Fabricius to body weight ratio and foot pad lesion scores were determined at 2, 4, 6 and 8 weeks of age, and bone development at 6, 7 and 8 weeks. Birds on free-range production system recorded significantly lower adrenal gland-to-body weight ratios than those in confinement (P < 0.05). The longer the birds were on the free-range production system, the larger was their bursa-to-body weight ratio and the difference was significant between treatment A and D and treatment A and C at week 6 (P < 0.05). Bone ash (%) increased with exposure to free-ranging. There was a significant difference (P < 0.05) between tibia ash (%) of the control treatment D and that of treatments A and B. There was also a significant difference (P < 0.05) between tibia ash (%) of treatments A and C at week 6, 7, and 8. There was a positive correlation between tibia ash (%) and the ratio of inner diameter of the tibia to outer diameter expressed as a percentage (Spearman’s correlation of R=0.56). Birds under confinement had severe footpad lesions and the severity reduced with increase