UNIVERSITY PARK, Pa. — In poultry houses where broiler chickens — birds bred and raised specifically for meat production — are grown, feed is delivered through long feed lines, which are mechanized systems that automatically deliver feed from storage silos to feeding pans. They run from the front of the houses to the back, and sometimes nutrients become unevenly distributed. This can lead to inconsistent feed quality, which can affect bird growth and health. To help the poultry industry determine the extent of this problem, researchers at Penn State conducted a study of how nutrient distribution affects broiler chicken performance, processing yields and bone mineralization.
“Walking through commercial poultry houses, and looking in the feed pans, seeing what the birds are consuming, we saw a difference in the quality of feed from the front of the house where feed was coming in to the back end of the house,” said John Boney, Vernon E. Norris Faculty Fellow of Poultry Nutrition in the College of Agricultural Sciences, senior author on the paper. “That led us to the question: If we can see a difference in physical quality of the feed — meaning many of the pellets have broken down into fine particles or dust — how does that variability affect nutrition the birds get?”
In findings available online that will publish in the December issue of Journal of Applied Poultry Research, the researchers reported that variability in two key nutrients along the feed line affect broiler chickens’ growth performance, including body weight, feed-conversion ratio, processing yields — like breast meat yield — and bone strength/mineralization. The two key nutrient areas are amino acid density — the amount of essential amino acids, which are the building blocks for proteins, in the feed — and Phytase Activity, which is a type of protein called an enzyme responsible for initiating and accelerating necessary biological reactions — that helps chickens absorb phosphorus from plant material.
The researchers fed young commercial broiler chickens different diets for more than two weeks. The diets had two levels of amino acid density and three levels of the enzyme Phytase Activity. To make sure the dosing was precise, the enzyme was removed at the feed mill and added later.
The researchers found that birds on high amino acid density diets gained more body weight by the end of the experiment, they had better feed efficiency — which measures how effectively birds convert feed into weight gain — and they had higher breast meat yield.
On the other hand, the enzyme Phytase Activity had no significant effects, the researchers reported. Changing phytase levels didn’t impact growth, feed efficiency or bone health. The researchers concluded that amino acid density is a good indicator of nutrient segregation — when the density is wrong, bird growth and health suffer.
They also found that amino acid density and Phytase Activity didn’t interact, so observed effects could be reliably attributed to just amino acid density.
The takeaway message from the research, according to Boney, is that to assess feed-quality consistency in poultry houses — which typically house 25,000 to 40,000 birds — monitoring amino acid density is more informative than monitoring the level of the enzyme Phytase Activity, and that feed pellet quality and feed line length can cause important nutrient inconsistencies, affecting broiler chicken growth and health outcomes.
“Feed is carefully formulated for broilers, to make them grow quickly and be healthy, and as the poultry industry continues to grow, raising more and more birds, it’s important that feeding methods are consistent and uniformly effective,” Boney said. “If we can minimize or eliminate nutrient segregation, all the birds, regardless of where they're reared in a chicken house, have access to the same nutrients, and in theory, could grow at the same rate, making that flock more uniform in terms of size and health. So, it helps producers operating a processing plant satisfy orders.”
Brendan Liebross, graduate student in animal science, was first author on the study. Darby Boontarue, graduate student in animal science, and Courtney Poholsky, who earned a doctoral degree in animal science from Penn State in May of 2024, contributed to the research.
The research was funded by the PA Poultry Research Checkoff program and the U.S. Department of Agriculture’s National Institute of Food and Agriculture.