Effects of grinding method, particle size, and physical form of the diet on gastrointestinal morphology and jejunal glucose transport in laying hens

Several studies illustrated that the struc- ture of feed, i.e., the particle size, particle-size distribu- tion, and the physical form of the diet, affects the avian gastrointestinal function and health leading to changes in productive performance. However, investigations concerning the effects of feeding differently processed diets on laying hens are limited and primarily concen- trated on bird performance. The current study exam- ines the effect of feed processing on the gastrointestinal morphology and on the jejunal glucose transport of lay- ing hens. In 8 replicates, a total of 384 hens (Lohmann Brown) aged 20 wk were randomly allocated to 8 dif- ferent groups and fed over a period of 21 d in a 3-facto- rial design. Diets differed in 1) grinding method, either hammer or roller mill; 2) physical form, either mash or expandate; and 3) particle size, either coarsely or finely ground. During the experimental trial, the laying performance of each feeding group was recorded daily and the feed intake and BW determined weekly. After slaughtering, the weights of the pancreas, proventricu- lus, gizzard, and small intestine were measured. Villus lengths and crypt depths of the duodenum, jejunum, and ileum were determined. The jejunal electrogenic glucose transport was studied in Ussing chambers. Hens that received mash instead of expandate had higher proventriculus (P = 0.011), gizzard (P < 0.001), and pancreas (P = 0.019) weights, whereas the feeding of coarsely instead of finely ground diets led to higher giz- zard weights (P < 0.001). Mash-fed hens showed longer duodenal (P < 0.001) and shorter ileal villi (P = 0.047) and increased duodenal villus height-to-crypt depth ra- tios (P < 0.001) than those given the expandate. Mash- fed hens had higher glucose transport rates than expan- date-fed hens (P < 0.001). In conclusion, the feeding of coarsely ground as well as mash diets had stimulat- ing effects on the development of the gastrointestinal organs. Moreover, the feeding of mash influenced the intestinal microstructure of the epithelium that was ac- companied by higher glucose transport capacities.