Dimensions and histologic characteristics of the small intestine of dogs during postnatal development

Objective-To quantify dimensions of the small intestine of dogs and describe changes in histologic characteristics of the mucosa during postnatal development. Sample Population-Gastrointestinal tract tissues obtained from 110 Beagles (15 adult females and 95 puppies of both sexes). Procedure-Several variables (length, total weight, mucosal weight, and nominal surface area) of the small intestine were measured in puppies at birth but before suckling- 1 day after birth and subsequent suckling, 21, 4, and 63 days after birth, and in the adult dams of the puppies. Tissue structure was examined and quantified at each time point by use of routine histologic examination and ocular micrometry of formalin-fixed specimens stained with H&E. Results-Small intestinal dimensions increased throughout development with the greatest proportional changes during the first day after birth and onset of suckling. Villus height decreased during suckling but had consistent values from 42 days after birth to maturity, whereas crypt depth increased from birth to maturity. Vacuolated enterocytes were evident from birth to 21 days but not thereafter. Conclusions and Clinical Relevance-Increases in intestinal dimensions provide growing dogs with a greater capacity for digestion and absorption. Changes in mucosal architecture and cell populations coincided with shifts in dietary inputs. These findings may assist in the diagnosis of small intestinal diseases and nutritional responses during growth and development of dogs.