Age‐related Effects of Feeder Space Availability on Blood Physiological Variables of Broilers Grown to Heavy Weights (> 3 kg)

Abstract

Demand for and consumption of poultry meat has increased dramatically, and is expected to continue in the future due to the relative price‐competitiveness as compared to other meat products. Consumer concern about rapid growth and increased production efficiency is perceived to negatively impact the well‐being of the animal. Hematological analyses including changes in acid‐base balance provide a thorough evaluation of the health status of individuals; and changes are the indicators of internal organ health and systemic homeostasis in both domestic animals and human beings. This study investigated the effects of feeder space availability on blood physiological variables of broilers grown to heavy weights (> 3.0 kg). A total of 1440 1‐d‐old chicks (straight‐run) were obtained from a commercial hatchery. Chicks were equally and randomly allocated to 32 pens based on feeder space treatment assigned. Treatments were four different feeder space allocations: 2.30 (Single feeder), 2.30, 4.60, and 6.90 cm/bird. In order to maintain uniform bird:feeder floor space except for the single feeder, three feeders were installed in each pen. Blood samples (3 ml) were collected from the brachial wing vein of 3 birds per pen on d 27 and 55, which were then analyzed immediately for whole blood physiological variables. The remaining blood samples were centrifuged to collect plasma that was used for corticosterone analysis. Results show there was no effect of feeder space on most of the selected physiological variables, but age had significant effects on most of the examined variables. However, all observed changes were within physiological ranges. Plasma corticosterone was not affected by feeder space and age, indicating absence of physiological stress. The results are in broad agreement with those reported in the literature and contribute to our knowledge of blood physiological and homeostatic variation in developing broilers. In conclusion, expanding feeder allowance does not enhance the welfare of broilers grown to heavy weights.