The Effects of the Hot, Humid Tropical Climate and Early Age Feed Restriction on Stress and Fear Responses, and Performance in Broiler Chickens

A Al-Aqil,I Zulkifli,A R Omar,M A Rajion,A Q Sazili

doi:10.5713/ajas.2009.90021

Abstract

The present study was conducted to determine the effects of two types of housing systems and early age feed restriction on stress and fear reactions, and performance in broiler chickens raised in a hot, humid tropical climate. On day 1, chicks were housed either in windowless environmentally controlled chambers (temperature was set at 32°C on day 1 and gradually reduced to 23°C by day 21) or in conventional open-sided houses (OH) with cyclic temperatures (minimum, 24°C; maximum, 34°C). An equal number of chicks from each housing system was subjected to either ad libitum feeding (AL) or 60% feed restriction on day 4, 5 and 6 (FR). The CH birds showed greater weight gain, higher feed consumption and better feed conversion ratios (FCR) than their OH counterparts. Feeding regimen had negligible effect on overall performance. Neither housing nor feeding regimen had a significant (p<0.05) effect on mortality rate. Although the CH birds were less stressed, as measured by plasma corticosterone concentration (CORT), than those of OH, the former showed longer TI duration suggesting higher magnitude of underlying fearfulness. A significant (p<0.05) effect of housing on heterophil/lymphocyte ratios was only noted among the AL birds where the CH birds had higher values than OH. Collectively, these results suggest that although OH birds had poorer performance and higher level of stress than CH, the former were less fearful. Although FR had negligible effect on growth performance, the regimen alleviated both stress and fear reactions in broilers.

Highlights

Tropical countries like Malaysia are constantly facing the challenge of excessive heat and humidity
Feed conversion ratios of FR birds were significantly better than their ad libitum feeding (AL) counterparts from day 1 to 14
The CH birds had significantly (p

Summary

Introduction

Tropical countries like Malaysia are constantly facing the challenge of excessive heat and humidity. Depressed growth rate and decreased feed consumption of broilers raised in higher temperature environments have been reported in many studies over a number of years (Daghir, 1995a). In Malaysia where the ambient temperature ranges from 24°C to 34°C, maintaining an optimum climatic environment in a conventional open-sided house is a Previous studies (Zulkifli et al, 1994a, b, 2000a) under artificially controlled conditions have consistently shown that early age feed restriction enhanced the ability of chickens to withstand high ambient temperatures as juveniles than those fed ad libitum throughout the experiment. The only reported study on early age feed restriction and heat tolerance in chickens under the natural tropical hot, humid conditions is by Zulkifli et al (2004). The authors reported that the early age feed restricted birds had better cumulative feed conversion ratios, and survivability rate than those fed ad libitum throughout

Methods

Results

Conclusion