Results and Discussion
Calculated and analyzed values for CP and amino acid
content are shown in Table 2. Analyzed CP values for all
diets were in good agreement with the calculated
values. Analyzed levels of all supplemental amino acids
were all in close agreement with the calculated values.
The amino acid content in all diets was higher than the
NRC (1994) recommendation for essential amino acids.
Reduction of CP level in the diets had a significant
influence on the live performance of male broilers (Table
3; Fig. 1). As noted in the previous results from our
laboratory, a reduction in the dietary crude protein to levels lower than 22% resulted in a significant reduction performance when added to diets with 16 or 18% CP.
in the BW gain and an increase in the FCR even though The FCR of birds fed the 18% CP diet supplemented
the low CP diets were formulated to provide a minimum with the EAA mixture did not differ significantly from that
of 110% of NRC (1994) amino acid recommendations. of birds fed the 22% CP diet but was significantly less
Addition of a mixture of EAA to bring total dietary levels than that of birds fed the diet with 24% CP. The
equal to that of the 22% CP diet improved performance improvement in FCR of chicks fed the 16% CP diet
slightly when added to the 20% CP diet and significantly supplemented with the EAA mixture was equal to that
when added to diets with 16 or 18% CP. Chicks fed the obtained on the 18% CP diet but was less than that
EAA-supplemented 18 and 20% CP diets did not differ obtained on diets with 22 or 24% CP.
significantly in BW from those fed the 22% CP diet but Addition of the NEAA mixture to provide N equivalent to
were significantly lighter than those fed the 24% CP that from the EAA mixture had variable results. There
diets. Addition of the mixture of NEAA to equal the N was no apparent benefit observed when added to diets
content of the EAA mixture also improved the BW of with 20% CP but a significant improvement when added
chicks fed the 20% and 16% CP diets but had no effect to diets with 18% CP. Addition to the diet with 16% CP
on BW of chicks fed the 18% CP diet. resulted in a numerical but nonsignificant improvement
Reduction in dietary CP had a significant effect on feed in FCR.
conversion by male broilers (Table 3; Fig. 2). Decreasing The nitrogen excretion significantly decreased as the CP
the dietary CP resulted in significant increases in FCR at levels declined, but was increased by the addition of
each reduction in dietary CP level. Addition of a mixture mixtures of EAA or NEAA at each level of CP (Table 3;
of EAA to bring total dietary levels equal to that provided Fig. 3). The increased N excretion that resulted from
by the 22% diet had no significant effect when added to addition of the mixtures of EAA or NEAA suggests that
the diet with 20% CP but significantly improved the supplements were not totally used to support protein