The Effect of Crude Protein Intake on Poultry Average Daily Gain
Daphne Ardizzone, Cody Gerber, Stephanie Hucko, Kedrick Miller, and Jamie Pozezinski
ANSC 324 Group 2 9:30 A.M.
This study was conducted to determine if decreasing dietary crude protein (CP) would decrease
average daily gain (ADG) in broilers.
Three different types of diets each having a different
amount of CP were fed to two replicate cages of five chicks per cage from day 1 to day 14.
Chicks were weighed every seven days for two weeks.
The CP levels for diets 1 (control), 2, and
3 were 23.0, 20.5, and 19.1 %, respectively.
The control diet was formulated to meet NRC (1994)
requirements for CP and the other diets were formulated to meet minimum NRC requirements for
amino acids with the addition of synthetic amino acids.
Data were analyzed using t-tests for equal
The result from our experiment indicated that between day 1 and day 14 decreasing
CP with the supplementation of synthetic amino acids from 23.0 to 19.1 % does not affect broiler
The most recent NRC (1994) lists the crude protein (CP) requirement of 0-3 week old broilers as
23%. Previous experiments have reported that decreasing dietary CP resulted in a decrease in
average daily gain (ADG) (Bregendahl 2002). In addition to this, Bregendahl et al. (2004)
reported a decreased feed efficiency and growth rate when low protein diets were fed to
broilers. To replace the loss of CP and still maintain growth, synthetic amino acids can be used to
meet the requirements for the limiting amino acids. Jiang et al. (2005) demonstrated that diets
low in CP can be supplemented with synthetic amino acids to maintain performance. The NRC
(1994) recommendations for CP are based on the amount of CP that needs to be in the diet to
meet the requirements of essential amino acids present in the diet. This is done, assuming that
no synthetic amino acids are supplemented to the diet and all amino acid sources are from typical
ingredients that are fed to poultry commercially. It was observed that adding the synthetic amino
acid glycine to diets low in CP prevented decreases in body weight due to a deficiency of glycine
(Waldroup et al., 2005).
Our hypothesis was that by decreasing dietary CP with supplementation
of synthetic amino acids, ADG would be reduced. To test our hypothesis, we used 30 male
broilers obtained on the day of hatch in a 14 day experiment to determine whether ADG and
average daily feed intake (ADFI) would be affected by decreases in dietary CP.
Thirty, day-old, male, broilers were randomly allocated to 6 cages with 2 cages per diet and 5
birds per cage. Birds were placed in Petersime battery cages with nipple waterers, trough
feeders, and surface tension waterers. Pen body weight and feed intake were recorded on the
first day and at the end of the first and second week. Birds had unlimited access to feed and
water. Diets 1, 2, and 3, were formulated to contain 23.0, 20.5, and 19.1% CP,
respectively. These values and ingredients were chosen to determine whether the amount of CP
in a diet would affect growth rate. T-tests were used to determine the effects of the diet on ADG,