Histomorphometric analysis of the small intestine in Philippine Darag native chickens compared to slow-growing commercial broilers

The Philippine Darag native chicken demonstrates favorable health and welfare indicators that are comparable to those of slow-growing Redbro broiler chickens. This study analyzed the histomorphometric characteristics of the small intestinal segments in these 2 breeds over an 8-week growth period. Small intestinal samples were collected weekly from both breeds from week 1 to week 8. Tissues were fixed and stained with hematoxylin and eosin, and analysis was performed using ImageJ to quantify villus height (VH), crypt depth (CD), villus-to-crypt ratio, epithelial thickness (ET), mucosal thickness (MT), and tunica muscularis thickness. The effects of age and breed, as well as their correlations with body weight, relative organ weight, and total feed consumption, were evaluated using a mixed-effects model, Pearson’s correlation, and multiple linear regression. Additionally, a binomial logistic regression model was applied to examine the occurrence of zigzag villi patterns. All histomorphometric parameters exhibited a significant increase with age. Redbro displayed earlier and more rapid intestinal development, whereas Darag demonstrated slower yet more comprehensive maturation across parameters. The zigzag villi pattern emerged earlier in Redbro, particularly in the jejunum. The identified age- and breed-specific differences in small intestinal development suggest that intestinal adaptation may contribute to variations in growth performance and may indicate potential advantages to Darag in low-input production systems. Furthermore, the significant correlations of VH, CD, ET, and MT with production indices indicate that growth performance is influenced by a complex interaction of absorptive capacity, intestinal health, and motility, rather than solely by villus surface area.