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The experimental work of the present study was conducted at the Poultry Farm; Agricultural researches and Experiments Station; Faculty of Agriculture, Mansoura University, Egypt. The experimental feeding trial of this study was carried out during the period from June to August 2000. The aim of the study was to investigate the possibility of alleviating the adverse effects of heat stress to which broiler chicks are exposed during the summer season by means of early-age feed restriction (EFR) and dietary supplementation with potassium chloride (KCl), either singly or in combination. A total number of 360 one-day old, broiler-type Hubbard chicks were randomly divided into two halves, each of which was assigned to four treatments (T), and given isonitrgenous and isocaloric starter diets (21.6% CP and ME of 3000 KCal/kg) from 0 to 3 weeks of age and grower diets (19.6% CP with ME content of 2955 KCal/kg) between 3 to 6 weeks of age. Two feeding regimens were imposed on these birds. Chicks of the first half (treatment groups of T1, T2, T3 and T4) were full-fed (FF); on ad libitum basis, during the entire experimental period from 0 to 6 weeks of age.

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