Appreciating the Dynamics of Pellet Quality Improvements to Nutrient Segregation in Poultry Houses

Feed ingredients and manufacturing are expensive components of integrated poultry production, sometimes reaching 70% of total operational costs. Fortunately, the added costs of manufacturing poultry feed improve feed efficiency and poultry performance. The performance benefits from feeding pelleted diets results in a positive return on investment, making it a common practice in broiler and turkey production. Improving the quality of pellets further enhances poultry performance and may offer a more uniform feed as it is conveyed throughout the house. Many factors contribute to a feed mill operator’s ability or willingness to improve pellet quality such as throughput demands and the lack of association between pellet quality, performance, and economics. However, a considerable amount of recent pellet quality research supports improved feed intake, body weight gain, and feed efficiency when birds are provided high quality pellets. New perspectives on pellet quality are needed to support investments in the manufacturing process. Sellers et al. (2020) studied nutrient segregation in 58-m broiler houses and reported varying levels of phytase enzyme activity in feed pans. Phytase enzyme activity depended on the ratio of pellets and fines in the feed pan, suggesting that phytase may be a suitable marker for nutrient segregation. Considering the precision of modern broiler diet formulations, it became apparent that segregation of other nutrients should be explored. Four experiments were conducted to represent four different scenarios where feed line length and pellet quality differed in each scenario. The objectives of this paper are to offer nutrient segregation mitigation strategies to feed mill operators and poultry producers.

Poultry producers in integrated operations finance the houses built on their property and contribute to house design and equipment installation decisions. It is common for feed bins to be located at the end of barn, having feed lines running the length of the barn. It is also common for feed bins to be centrally located, having feed lines running from the center of the house to either end. The difference is the distance feed travels in each scenario. Mechanical forces acting on the feed during conveyance contributes to pellet breakdown. Improving pellet quality minimizes the breakdown of pellets during transport and conveyance. Nutrient segregation was studied in two commercial broiler houses depicted in Figure 1. The four scenarios were:

- Poor pellet quality in long (152-m) feed lines

- Improved pellet quality in long (152-m) feed lines

- Poor pellet quality in short (76-m) feed lines

- Improved pellet quality in short (76-m) feed lines

To determine if nutrient segregation was occurring in each scenario, feed samples were collected from defined regions of each feedline. Each scenario was studied in four replicate feed lines. This allowed for a simple analysis of variance between each region of the feedline. Samples were sieved to determine the ratio of pellets and fines. Pellet durability analysis was performed on pellets samples. Pellet and fines samples were analyzed for the concentration of 12 amino acids as well as phytase enzyme activity at commercial laboratories. No broilers were in the barns during feed augering or sampling. Therefore, nutrient segregation effects on broiler performance were not measured in these four scenarios.

Figure 1. Schematic of replicate feed line regions at each farm. Arrows indicate feed flow direction at each farm. Commercial houses at farm 1 consisted of four 152-m-long feed lines equipped with 192 feed pans per line. Eight regions were created and consisted of 24 feed pans. In the diagram, a single feed pan represents six feed pans. The 152-m-long commercial house at farm 2 consisted of center of house fed feed lines, creating four 76-m-long feed lines with 95 feed pans per line. Feed was augered into centrally located feed hoppers and pulled to either end of the house. Each region consisted of 12 feed pans.

In this scenario where poor-quality pellets were augered a long distance, nutrient segregation was apparent. Of the 12 measured amino acid concentrations, six of these amino acid concentrations varied across the 152-m feed line. Aspartate concentrations varied by 10.8%, glutamate by 12.8%, glycine by 7.8%, leucine by 7.4%, alanine by 6%, and lysine by 9.4% across the eight regions of the feed line (Table 1). Phytase segregation was also apparent with phytase activities varying by 50.3% across the eight regions of the feed line. In addition, pellet durability and the percentage of pellets in the feed pan varied by 5.6% and 10.6%, respectively.

Table 1. Nutrient segregation in long (152-m) feed lines conveying poor-quality pellets

In this scenario where improved-quality pellets were augered a long distance, only aspartate and glutamate concentrations varied (9.4% and 9.8%, respectively) across the eight regions of the feed line (Table 2). Pellet durability varied by 4.6% while phytase enzyme activity and the percentage of pellets in the feed pan were similar in this scenario. Improving pellet quality appears to decrease amino acid, phytase, and feed particle segregation when augering feed long distances.

Table 2. Nutrient segregation in long (152-m) feed lines conveying improved-quality pellets

In this scenario where poor-quality pellets were augered a short distance, threonine was the only amino acid concentration that varied (11.7%) across the eight regions of the 76-m feed line (Table 3). Phytase segregation was apparent in this experiment, where enzyme activity varied by 64.7% between region 2 and region 8. These data suggest that even when augering feed a short distance, applying phytase products to poor quality pellets results in enzyme activity variability from feed pan to feed pan.

Table 3. Nutrient segregation in short (76-m) feed lines conveying poor-quality pellets

In this scenario where improved-quality pellets were augered a short distance, neither amino acid nor phytase segregation was apparent (Table 4). The percentage of pellets in the feed pan was the only measured variable that differed across the eight regions of the feed line.

Table 4. Nutrient segregation¹ in short (76-m) feed lines conveying improved-quality pellets

Both the quality of the pellet and the length of feed conveyance affects the profile of nutrients present in feed pans. A summary of nutrient segregation in the four scenarios is found in Table 5. As broilers progress through their production cycle, they travel a shorter distance (Dawkins et al., 2012). Therefore, it is plausible that on-farm nutrient segregation affects broiler performance in later phases of production when feed intake is high, and distance traveled is low.

When studying the four scenarios in the current study, phytase segregation appeared to be affected largely by pellet quality. Walters et al. (2019) explained that higher doses of phytase improves performance, nutrient digestibility, and bone mineralization. Boney and Moritz (2017) explained that phytase dose affects may depend on ingredient composition. These papers support feeding similar levels of phytase enzymes to improve flock performance and uniformity. This may be most easily achieved by working with feed mill operators and nutritionists to create finished feeds with a greater percentage of pellets in the feed pan.

The four scenarios in the current study also indicated that amino acid segregation could be managed by shortening the distance that feed is conveyed or by improving pellet quality. Corzo et al. (2010) demonstrated that performance and yield were affected by amino acid density, especially in later phases of production. Furthermore, Kidd et al. (2005) explained how decreasing amino acid density reduced body weight, feed efficiency, and yields and suggested that optimizing amino acid nutrition in early production phases is critical. Once again, working with feed mill operators and nutritionists to create finished feeds with higher quality pellets is advised. If improving pellet quality is not possible, poultry producers are able to contribute to reduced nutrient segregation, flock performance, and flock uniformity by positioning feed bins near the middle of the barn so that feed is conveyed a shorter distance.

Table 5. Summary of nutrient segregation in commercial broiler barns