P2.86 Thursday, Jan. 5 Lactating Columbian ground squirrels increase nutrient absorption without altering digesta retention RAMIREZ, Matthew*; SKIBIEL, Amy; HOOD, Wendy; Auburn University; Auburn University; Auburn University firstname.lastname@example.org
During lactation, a mother must support the nutritional demands of both herself and her dependent offspring. To meet this demand, mothers often increase food intake. However, without changes in gastrointestinal morphology, mean digesta retention time and relative digestibility will decrease and ultimately, intestinal capacity may limit reproductive performance. During reproduction, an increase in mass and length of the small intestine can compensate for increased nutrient intake and a change in handling of solute versus particle phases of digestion may improve nutrient absorption. The purpose of this study was to examine the functional changes in the gastrointestinal tract during lactation in Columbian ground squirrels. Digestibility of dry matter, fiber, and nitrogen was compared between early and late lactation females, and between lactating and non-reproductive females. Food and feces were analyzed for dry matter fiber content and nitrogen. To examine mean retention time, the passage of two digesta markers (Co and Cr) was quantified at peak lactation. Food intake and digestion of fiber components and nitrogen in the diet was significantly greater in lactating females over non-reproductive individuals. This improved digestibility by reproductive individuals was not associated with an increase in the amount of time that solutes or small particles were retained in the gastrointestinal track. However, within each group, solutes were selectively retained over particles, an adaptation previously thought to be limited to small species (<100 g). These findings suggest that greater absorption efficiency in lactating females is most likely achieved with an increase in the efficiency of passive and active absorption rather than with changes in gross morphology.