effect of feed form on performance, gut morphology and cecal microflora on late-phase laying hens under cyclic high ambient temperature

Feed form and heat stress (hs) are two major critical issues that affect feed intake (fi) in poultry. limited research has been conducted on the impact of feed form on the intestinal morphology of laying hens. additionally, the influence of feed form on the intestinal microbiota of laying hens under hs conditions remains unexplored.  one hundred and forty-four laying hens (90 weeks of age) were used in a completely randomized design with two treatments (pellet and mash). each treatment contained six replicates of 12 hens each. laying hens were subjected to a cyclic heat stress regimen of 32 ± 3°c for 6 hours per day at a humidity of 35–40% during the late laying period (weeks 90–97). feed form had no effect on egg production and feed conversion ratio (p>0.05), but egg weight and mass, fi, and body weight gain increased in the birds fed the pelleted diet (p<0.05). feeding the pelleted diet decreased the shell weight and thickness, as well as the yolk color score (p < 0.05), but did not affect other egg quality parameters (p>0.05). villus width and villus surface area were higher in hens fed the pelleted diet (p<0.05) than those fed the mash diet, but villus height, crypt depth, and the villus height-to-crypt depth ratio were not affected by the treatments (p>0.05). there were no significant differences between treatments regarding cecal bifidobacteria spp. lactobacillus spp. and coliforms populations (p>0.05). however, feeding laying hens with pelleted diet resulted in greater numbers of cecal enterococcus spp. compared to those fed the mash diet (p<0.05). this study indicated that feeding the pelleted diet improved the egg mass production and intestinal morphology, reduced the shell weight and thickness, and increased the population of enterococcus spp. in the ceca of late-laying hens exposed to hs. the economic benefit from performance improvement with the pelleted diet may have offset the higher feeding cost.