A trial was conducted to determine the effect of low-protein diets with constant ME:CP
ratio on performance and carcass characteristics of broilers from 1 to 35 d of age.
Four experimental diets were formulated to have 4 levels of CP and ME, respectively,
in each phase: 23, 22, 21, and 20% CP with 3,036, 2,904, 2,772, and 2,640 kcal/kg
in the starter phase (1 to 10 d); 22, 21, 20, and 19% CP with 3,146, 3,003, 2,860,
and 2,717 kcal/kg in the grower phase (11 to 26 d); and 20, 19, 18, and 17% CP with
3,100, 2,945, 2,790, and 2,635 kcal/kg in the finisher phase (27 to 35 d). Digestible
Lys was maintained at 1.10, 1.02, and 0.90% of the diet in the starter, grower, and
finisher periods, respectively. A total of 1,760 one-day-old Hubbard broiler chickens
were randomly divided into 16 experimental pens, 110 chickens in each pen, and each
diet was offered to 4 replicates at random. Weight gain was linearly decreased (P
< 0.001), whereas feed intake and feed conversion ratio were increased (P < 0.001)
linearly as dietary protein and energy decreased during grower, finisher, and overall
experimental periods. Protein efficiency ratio and energy efficiency ratio were decreased
(P < 0.05) with low-CP and low-ME diets during the grower, finisher, and overall experimental
period. However, carcass yield, breast meat yield, thigh yield, abdominal fat, and
relative liver and heart weights were not affected by the treatments. Feeding broiler
chickens low-CP diets with constant ME:CP ratio has adversely affected the growth
performance, but carcass parameters were unaffected without any increase in abdominal
fat content.