Optimizing broiler growth and health requires a diet that delivers uniform nutrients to all birds. But that involves more than getting the diet formulation right. It’s also influenced by the feed bin and delivery systems, which determine the final product the birds receive in the barn.
The feed mill has quality-control steps to measure diet uniformity post-mixing. But what happens once that feed leaves the mixer? That’s the question Courtney Poholsky, PhD candidate and research assistant at Pennsylvania State University, addressed at the 2024 International Poultry Scientific Forum.
Pellets can break down at the feed mill, during transportation, in feed-storage bins and throughout the poultry house as feed is augured through the lines. “Post-mixing variations can change the diet’s uniformity once the feed has been discharged,” she said.
“Pellet migration can lead to subsequent segregation of nutrients throughout the poultry house, which impacts individual bird performance and bodyweight uniformity of the flock,” Poholsky added.
Study details
The Penn State poultry lab has conducted field studies on feed and nutrient distribution in commercial broiler houses, finding that the initial pellet-to-fine ratio and feed-line length impact nutrient segregation.
In the latest study, Poholsky and colleagues evaluated feed flow within the storage bins and the impact of nutrient segregation on flock performance. They assessed on-farm feed and nutrient distribution over 5 days and examined the relationships between feed-bin dynamics, feed and nutrient flow and broiler bodyweights.
Throughout the study, the researchers fed the chickens a commercially formulated withdrawal diet sourced from a feed mill known to produce a low pellet-to-fine ratio (65% pellets, 35% fines).
“Diet uniformity should be tested at the point of consumption,” Poholsky said.
The broiler house was equipped with two 150-meter-long feed lines, with 10 feed-pan sections for each line, representing 15 linear meters. Poholsky collected feed from three centrally located feed pans within the 10 sections of the two feed lines, totaling 60 daily feed samples.
To collect samples, Poholsky emptied the selected feed pans to remove any leftover feed dust, litter and feathers. At 8 a.m. on collection days, she raised the feed lines and activated the motors for about 30 minutes. Researchers sent the samples collected from the feed pans to Penn State where they were sifted to determine the pellet-to-fine ratio.
Next, they combined pellets and fines, grinding each sample to determine gross energy levels and calibrate for withdrawal feed to obtain a predicted outcome, Poholsky explained.
“We analyzed the composite feed samples for each feed-pan location per feed line at commercial laboratories for total amino acids, phytase activity and minerals,” she added.
The researcher team decided to reduce the number of feed-pan locations to three for data analysis, representing the front, middle and back of the house. This reduction aligned with divisions created by two migration fences.
“In addition to feed analysis, we recorded feed-bin inventories each day, as well as broiler bodyweights, in the front, middle and back of the house,” Poholsky said.
Pellet and nutrient segregation
Feed pans in the front of the house had fewer pellets than the middle or back sections for each of the 5 collection days. “We observed an 18-percentage-point increase in pellets as the feed traveled from the front to the back of the house,” Poholsky noted. The pellet levels augured into the poultry house also increased over the 5 days.
“To explain this variation, think about how feed flows inside the feed bin,” she said. “We recorded feed-bin levels at the end of each collection day; the bins started at 85% full and dwindled to 4% full by day 5. Thus, as feed is discharged from the bin, different ratios of pellets and fines will enter the poultry house.”
Regarding nutrient data, crude fat varied by 5% throughout the barn, with the highest levels in feed pans containing the most fines. Poholsky acknowledged that some of the variation may have occurred because a portion of the soybean oil was applied post-pelleting.
Nutrient concentrations also varied by the sample collection day. Total lysine concentration decreased over the 5-day study, as did other amino acids and minerals. “Such daily variations should be considered when collecting on-farm feed samples,” she said. “Collect samples across a time period for a more accurate representation of the diet’s nutrient profile.”
Impact on performance
The researchers recorded broiler bodyweights in each of the three feed-pan locations throughout the 5 days, revealing that birds in the back of the house were 470 grams (1.04 pounds) heavier than birds in the front.
“The percent of pellets positively correlated with broiler bodyweights, indicating birds that consumed more pellets were heavier than birds that consumed less,” Poholsky noted. “Therefore, bird growth may depend upon the house’s location.”
She pointed out that the grower used a partial-house breeding strategy. The research team also conducted the study during the summer when ambient temperatures were high. Those two factors created a higher stocking density in the front of the house than in the back, which could have impacted feeder-space access and weight gain.
“Daily variations in the percentage of pellets and nutrients are attributed to feed flow within the feed bin,” she said. “This is important information for producers concerned about feed-quality variations.”
Poholsky recommended collecting feed samples throughout the poultry house at different locations and over time to provide decision-makers with accurate nutritional information.
She added that it may be helpful to investigate technologies that can be inserted into the feed bin to achieve a more uniform flow of the different particle sizes.
