The present study was carried out 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/or dietary
supplementation with potassium chloride (KCI). Three hundred and sixty, one-day-old,
broiler-type Hubbard chicks were randomly divided into two halves, each of which was
assigned to four treatments (T), and given starter diets from 1 to 21 days of age, then,
the birds were switched to grower diets from 22 to 42 days of age. Two feeding
regimens were imposed on these birds. Chicks of the first half (T1, T2, T3 and T4)
were full-fed (FF) during the entire experimental period from 0 to 6 weeks 0 fa ge,
while birds of the other half (T5, T6, T7 and T8) were subjected to feed restriction;
only dunnq the first week of life. Each of the starter and grower diets were isocaloric
and isonitrogenous, and originally contained about O.B% K. Diets of T1 and T5 were
unsupplernented with KCI and served as controls, while diets for chicks of T2 and T6,
T3 and T7 or T4 and TB, were supplemented with KCI at levels of 0.75, 1 5,and
2.25%, respectively. Thus, in these diets, supplemental K CI plus basal K provided
dietary K levels of O.B, 1.2, 1.6 or 2.0%, respectively. The criteria of response were live body weight, weight gain, feed intake, feed
conversion ratio, mortality rate, carcass traits, and economic efficiency. The obtained
results can be summarized as follows: Early feed restriction (during the first week) had
no significant effects on final body weight (at 6 weeks of age), weight gain, mortality
rate of chicks or their carcass traits, but significantly decreased feed intake and
improved the efficiency of feed utilization. Dietary KCllevels of 1.5 or 2.25% resulted
in significant increases In live body weight, improved the efficiency of feed utilization
of chicks and attained the lowest mortality rate, while carcass traits were not affected.
The use of early-age feed restriction, and/or supplemental KCI especially at a level of
1.5 or 2.25% reduced mortality rate, and improved weight gain and feed conversion of
chicks. But because the combination of early-age feed restriction and dietary inclusion
of KCI at a rate of 2.25% significantly improved the viability of chicks as evidenced by
no observed mortality, it had the advantages over the other treatments; for the sake of
safety and economic use under hot environmental conditions of summer season, as is                 the case of the present study.