THREE DIETARY PROTEIN LEVELS IN THE PRODUCTION OF SQUAB BROILER

Latorre, J. R.

Randel, Paul F.

Salas, Franklyn A.

English

Portal de Revistas Académicas Universidad de Puerto Rico

Research Note 
THREE DIETARY PROTEIN LEVELS IN THE PRODUCTION OF 
SQUAB BROILERS1 
Broiler chick production has been one 
of the fastest growing agricultural enter-
prises in Puerto Rico in recent years, yet 
even with this increase in local production 
the majority of the poultry meat consumed 
on the island is still imported.2 The con-
ventional broiler cycle from hatching to 
processing lasts about 7 weeks. Use of a 
shorter cycle to obtain better tasting meat 
of lower fat content and more efficient feed 
conversion might be a beneficial alterna-
tive for some local producers. Optimal 
feeding practices for short-cycle chick pro-
duction under local conditions might differ 
in some respects from those used in the 
conventional cycle. The objective of the ex-
periment reported here was to test 
isocaloric diets with three different crude 
protein (CP) contents for chicks processed 
at 4 weeks of age. 
One-day old chicks of a commercial 
line, vaccinated against marek, chicken-
pox, aviar tensionavities, New Castle and 
infectious bronquitis, were brought to the 
Agricultural Experiment station in Lajas 
in mid October. One week before the ar-
rival of the chicks, the housing facility was 
thoroughly cleaned and disinfected. Upon 
initial weighing, the chicks were divided 
into three groups of 67 each and placed in 
pens bedded with rice hulls and equipped 
with suspended watering troughs. Artifi-
cial heating was provided in each pen by 
means of a four-incandescent-bulb (60 
watts) heater. 
At night the shed also was artificially 
lighted. Feed in the form of 4 mm diameter 
pellets was weighed and placed in a metal 
tray on the floor. For 6 days each group was 
fed ad libitum one of the experimental diets 
A, B and C (table 1), formulated to contain 
20, 23 and 26% CP, respectively, and 3.14 
Meal metabolizable energy (MEn)/kg on 
the as-fed basis.3 This period of initial feed-
ing was to allow the chicks to become 
accustomed to the experimental diets. 
The study began by subdividing each 
of the original groups into three smaller 
groups of 20 chicks each to obtain three 
replications per treatment. Thus, 180 
chicks in nine pens were used. Extra 
chicks not needed were eliminated from 
the experiment. The birds continued to re-
ceive the same diets as previously, except 
that feed was in mash form during the 3-
week comparison period. Initial weights of 
the groups were recorded at this time for 
purposes of statistical evaluation. Artifi-
cial heating was discontinued. Suspended 
cylindrical feeders, periodically adjusted 
in height from the floor, were kept well 
supplied with the respective feeds. A sam-
ple taken from each lot of the diets was 
prepared for CP determination by micro-
Kjeldahl procedures. 
Before slaughter, feed was withheld 
from the chicks for 1 day and water was 
also withheld during the final hours. After 
live weight (LW) determination the chicks 
were moved, one group at a time, to the 
nearby abattoir. At slaughter the carcasses 
were immediately subjected to standard 
processing and dressed carcasses, without 
giblets, were weighed before refrigeration. 
Statistical analysis of the data was by a 
one-factor analysis of variance, applicable 
to an experiment of completely random 
design,4 
Submitted to Editorial Board 11 October 1993. 
"Boletín Informativo del Departamento de Agricultura de Puerto Rico, 1988. Ingreso 
Agrícola de Puerto Rico 1987-88. 
^National Research Council, 1984. Nutrient Requirements of Poultry. 8th rev. ed. 
National Academy Press, Washington, D.C. 
4Steel, R. G. D. and J. H. Torrie, 1980. Principles and Procedures of Statistics. 2nd 
ed. McGraw Hill Book Co., New York. 
51 
52 SALAS ET AL./SQUAB BROILERS 
TABLE 1. —Percentage formulas and analyzed crude protein content of the 
experimental diets 
Component 
Ground yellow maize 
Soybean meal 
Tunafish mea! 
Vegetable oil 
Salt 
Dicalcium phosphate 
Ground limestone 
Trace mineral and vitamin 
supplement 
Cocci diostat (Coban) 
Crude protein1 
A 
67.52 
14.50 
14.50 
2.00 
.50 
.40 
.30 
.20 
.08 
21.84 
Treatment 
B 
58.42 
18.50 
18.40 
3.20 
.50 
.40 
.30 
.20 
.08 
24.43 
C 
49.32 
22.40 
22.30 
4.50 
.50 
.40 
.30 
.20 
.08 
27.66 
•'Dry matter basis. 
Mean initial LW at 7 days of age of 
the chicks assigned to treatments A, B and 
C were 97.3,102.0 and 110.8 g. Table 2 pre-
sents treatment means during the 21-day 
comparison period. Treatment B (theoreti-
cally 23% CP diet) resulted in the greatest 
LW gain of 760 g, surpassing C and A by 13 
and 34 g, respectively. Daily gains were 
34.6, 36.2 and 35.6 g in A, B and C. These 
differences between treatments were not 
significant. Wilson et al. showed the di-
etary protein levels as low. as 12, 14, 16, 
and 18% had no significant effects on chick 
weight at 4 weeks of age. 
Differences in feed intake (20-day to-
tal) were not significant. Although the 
feed-intake/LW gain ratio indicated best 
efficiency for treatment B, which required 
.02 and .09 g less feed per gram of gain 
than C and A, respectively, these differ-
ences were not significant. In treatments 
A, B and C 0.37, 0.39 and 0.45g of CP were 
consumed per gram of gain, respectively. 
Korelesky and Rys6 found that the effi-
TABLE 2.—Mean live weight gain, feed intake, carcass weight and dressing percentage, 
and feed, intake per unit increase of liveweight and of carcass weight. 
Criterion 
Liveweight gain per chick 
Feed intake per chick 
Feed/gain ratio 
Dressed carcass weight 
Dressing percentage8 
Feed/carcass ratio3 
(g) 
(g> 
<8fe> 
(g) 
(g/g) 
A 
726 
1369 
1.88 
528 
64.10 
2.79 
Treatment 
B 
760 
1355 
1.79 
548 
63.56 
2.66 
C 
747 
1356 
1.81 
537 
62.57 
2,75 
SE 
10.2 
26.4 
0.03 
6.65 
— 
— 
aNot analyzed statistically. 
5Wilson, J. L. et al., 1984. Dietary protein levels for broiler breeder males. Poultry 
Science 63: 46. (Abstr.). 
bKorelesky, J. and R- Rys, 1980. Effect of reduced dietary protein and amino acid lev-
els on the performance of broiler chickens. Nutrition Abstracts and Reviews, Series B 50: 
376. 
J. Agrie. Univ. P.R, VOL. 78, NO. 1-2, JANUARY/APRIL 1994 53 
ciency of converting dietary protein to LW 
gain was up to 30% greater with low-pro-
tein feeds (14.8% CP) than with higher 
ones (22.1% CP), butNagabhushanam7 re-
ported that the said efficiency was best 
with 18 and 22% CP. The mortality rate 
during the comparison period was only 
1.67%. 
Differences in dressed carcass weight 
were not significant. Dressing percentage 
was highest for treatment A (64.10), while 
B and C had means lower by 0.54 and 1.53, 
respectively. These differences were not 
tested for statistical significance because 
they are too small to be of practical 
importance. 
The most important conclusion to be 
drawn from, these results is that a 22% CP 
diet, the level commonly used with broilers 
in the conventional cycle, is also satisfac-
tory for use in 4-week cycles at the dietary 
energy level in question. The additional 
cost that a higher protein diet would entail 
is not justified. Although treatment B (an-
alyzed 24.4% CP) resulted in the best LW 
gain, dressed carcass weight, and feed con-
version ratio, the present data were 
insufficient to prove that these small dif-
ferences were real. Even if real, the 
magnitude of the effects observed is too 
small to warrant a 3% higher dietary pro-
tein level, which would have a significant 
impact on least cost formulation. A combi-
nation of greater dietary concentrations of 
both CP and MEn might be beneficial and 
should be studied. With the management 
system used herein, it is possible to pro-
duce a Cornish hen-like chick with a mean 
LW of 850 g and dressed carcass weight of 
540 g in a 4-week cycle. 
Franklyn A, Salan 
Department of Animal, Science 
Paul F Randel 
Department of Animal Science 
José R. Latorre 
Department of Animal Science 
Nagabhushanam, N., 1980. Studies on protein and energy relationships in the diet 
of starter chicks. Nutrition Abstracts and Reviews, Series B 50: 105. 


THREE DIETARY PROTEIN LEVELS IN THE PRODUCTION OF SQUAB BROILERS

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THREE DIETARY PROTEIN LEVELS IN THE PRODUCTION OF SQUAB BROILERS

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