Broilers, which are granivorous birds, are quite susceptible to the sensory characteristics of the feed. The physical presentation, and more precisely, the particle size can have an impact on their feeding behaviour. For example, the switch from a crumbled to a pelleted feed, can be a critical period for these animals. Therefore, a good command of the presentation and physical quality of the feed is necessary for an adequate chicken growth performance.
Pellet hardness and durability
The physical quality of the feed can be influenced by many factors (formula, grind size, feed processing, etc...) and it is often evaluated using two different measures: pellet hardness and pellet durability. For example, Techna quality recommendation for broiler pellets, ranges from 75 to 80% for durability and less than 2.5kg* for hardness. On the one hand, a pellet that is too hard can result in feed sorting and wastage. On the other hand, a low durability with a high percentage of fines, can lead to digestive problems and litter degradation. Thus, a poor feed presentation may induce economic loss by declining broilers' growth rate.
Feed manufacturing process and physical quality of feed
In June 2020, Techna conducted a study through eleven French feed mills to better understand the relationship between the manufacturing process and the physical quality of broiler feed. In this study, regardless of the type of feed analysed, a positive linear relationship between pellet hardness and durability was observed. As the hardness increases by one point, the durability increases by 9.5 points.
These results demonstrate that in the starter diet, a high pellet durability before crumbling, reduces the fine fraction of the final crumble. In addition, a coarse grind (> 3.15mm) in the finisher diet, seems to negatively affect the quality of the pellet, by reducing its durability and its hardness. This fact can be explained by an increase of cracking points when particle size is high, decreasing the cohesion between these particles and eventually degrading the pellet.
In contrast, when the particles are small, a higher overall surface is available, and therefore a better agglomeration and stability of the pellet. The data also illustrates that pellet durability and pellet hardness are negatively impacted by the oil content of the formula, mainly when this oil is added during the mixing process.
In conclusion, the coarse grind, as well as the oil, seem to have a major impact on chicken feed quality. It is important to remember the importance of also monitoring intermediate products (such as pellets before crumbling), which can be key factors to complete a good management of the physical quality of broiler diets.
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