A total number of 675 one - day old unsexed Arbor Acres broiler chicks
were used to study the effect of dietary metabolizable energy ( ME ) and poultry fat
(PF) on broiler chick performance, nutrients digestibility coefficient and economic
efficiency during hot summer season. Birds were randomly divided into 9 equal
groups with three replicates of 25 birds each .Three levels of metabolizable energy
were used, being 3000 (low level) , 3100 (recommended level) and 3200 K cal ME
/ Kg ( high level) for growing period (1- 4 weeks of age) with constant crude protein
level ( 23 % ) .While, for finishing period ( 5 - 7 weeks of age) at 20 % crude protein,
3100 ( low level) , 3200 ( recommended level) and 3300 Kcal ME / Kg ( high level
).Each level of metabolizable energy was supplemented with three levels of poultry fat
in a 3 x 3 factorial arrangement to alleviate the side effects of heat stress (29-36 "C)
on broiler performance .The three levels of poultry fat were 0,3 and 6% of the diet
representing P F1,PF2 and P F3, respectively. T he birds were allocated in a littered
floor poultry house in an open system under the same conditions of management up
to 7 weeks of age. The overall results showed that the average values of body weight ( BW) ,
body weight gain (BWG), feed conversion ratio ( FCR ) and performance index ( PI )
were improved significantly ( P < 0.05 ) with high level of either metabolizable energy
or poultry fat especially during the finishing period . Data showed that only the
digestibility coefficient for both crude protein ( CP ) and ether extract ( EE ) were
improved significantly ( P < 0.05 ) when broiler chicks were fed diets containing high
level of either metabolizable energy or poultry fat .Results indicated that the average
values of abdominal fat increased significantly ( P < 0.05 ) with using high level of
either metabolizable energy or poultry fat .While, there were no significant differences
for both dressing, giblets and mortality rate values d ue to dietary treatments .Data
also indicated that using high level of either metabolizable energy or poultry fat
recorded higher values for economic efficiency compared with other experimental
groups. Therefore ,"it is suggested to increase dietary metabolizable energy more than
recommended level during both growing and finishing periods when adding fat up to 6
% of the diet to alleviate the side effects of heat stress on the performance of broilers.