Effects of particle sizes and physical form of the diet on performance, egg quality and size of the digestive organs in laying hens

The influence of feed form (mash, crumble and pellet) and screen size (5 mm and 8 mm) on laying performance, egg quality, digestive organ measurements and gizzard pH was examined in laying hens using a 3 x 2 factorial arrangement of treatments. Lohmann LSL-Classic white egg layers (n = 864) at 28 weeks of age were randomly divided into 6 dietary treatments, each with 6 replicates of 24 birds over the following 24 weeks period. Significant (P < 0.05) interactions between feed form and screen size were observed for egg mass output. Grinding ingredients through a screen size of 5 mm instead of 8 mm, as well as further processing of the feed mixture as mash and crumble increased egg mass, whereas a contrasting pattern was observed in the case of feeding on pellets. Egg production rate, egg weight, and cracked-broken egg rate were not affected by either particle size or form of the feed. Administering the diet in the form of pellet and crumble decreased feed intake of hens compared to mash (P < 0.01). The feed conversion ratio of hens fed on crumbled and pelleted diets was significantly lower (P < 0.01) than for those receiving a mash diet (P < 0.01). Egg quality characteristics were barely affected by either screen size or feed form. However, the consumption of feed in the crumbled and pelleted forms decreased the yolk colour score by 4% (P < 0.05). Screen size and feed form had no effects on the percentage weight of liver, gizzard, length of small intestine and gizzard pH. However, lowering screen size from 8 to 5 mm increased pancreas weight (P < 0.01). The overall results of this experiment suggest that feed form (mash vs. crumbles or pellets) had a greater effect on the FI and FCR of laying hens than dietary ingredient particle size, with the best efficiency of feed conversion being obtained from pellet-fed birds. The effect of particle size was pronounced for eggshell mineralisation and pancreatic functions.