SPECIAL STORY FEED & ADDITIVE MAGAZINE March 2022 63 sieve for the on-farm analysis that is mentioned in this article. The result of your feed sieve analyses will give you a fast and reliable reflection on the feed structure of the poultry diets. In feed mills, often more accurate dry feed sieves are used to check the structure after grinding and/or after mixing. THE EFFECT OF FEED PARTICLE SIZE ON THE DIGESTIVE TRACT The development of the digestive tract is heavily influenced by feed particle size. In general, chickens consuming feed containing large particles will develop bigger and more muscular gizzards, these birds will also develop longer intestinal tracts. The larger the feed particle, the more time the particle will spend in the gizzard. The function of the gizzard is to grind the larger feed particles into smaller particles before they can enter the small intestine. These larger feed particles have also longer transit time when passing through the gastro-intestinal tracts. It is known that birds that are fed with optimum particle sized diets have longer microvilli in their intestines. These longer microvilli result in increased absorptive surface areas, this directly affects the digestibility and nutrient absorption in a positive way. When the chicken feed is composed of too many fine particles (<1.0 mm), the fine feed particles will pass quickly through the gizzard as no (or limited) grinding is required. Once the particles have passed the gizzard, they will enter the proventriculus. The results of consuming diets that contain too many fine feed particles are a small gizzard, an enlarged proventriculus and reduced intestinal length. We strongly advise not to feed chicken diets containing too high levels of too fine particles! RECOMMENDED FEED PARTICLE SIZE Feed particle size has a large impact on the chickens' feed intake, dusty feed particles (<0.5 mm) will reduce feed intake greatly. We advise to increase the feed particle size with the age of the chicks. As the chicks grow, they will develop the size of their beaks, their gizzards, and the digestive tract. It is well known that laying hens are selective eaters: laying hens have a clear preference for the larger particles. The older the hen (the chick) becomes, the higher the preference for the larger feed particles. It is recommended to allow the birds time to finish the feed during the middle of the day, this will help to clean the feeders and to prevent the accumulation of small feed particles (referred as empty feeder technique). The larger feed particles are often the coarse grinded grains or corn, while the fine feed particles usually contain the vitamins, amino acids, phosphorus, and the essential trace minerals. As the fine particles play a crucial role in persistency of egg production and eggshell quality selective eating should be always prevented. As an egg producer you should carefully monitor the eating behavior of your flock. The empty feeder technique should already be applied after the first 4-5 weeks of rearing, as this will train the birds to eat well and develop a good crop.
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