Nutritional and Physiological Constraints Contributing to Limitations in Small Intestinal Starch Digestion and Glucose Absorption in Ruminants

Abstract

Increased efficiency of nutrient utilization can potentially be gained with increased starch digestion in the small intestine in ruminants. However, ruminants have quantitative limits in the extent of starch disappearance in the small intestine. The objective is to explore the nutritional and physiological constraints that contribute to limitations of carbohydrate assimilation in the ruminant small intestine. Altered digesta composition and passage rate in the small intestine, insufficient pancreatic α-amylase and/or small intestinal carbohydrase activity, and reduced glucose absorption could all be potentially limiting factors of intestinal starch assimilation. The absence of intestinal sucrase activity in ruminants may be related to quantitative limits in small intestinal starch hydrolysis. Multiple sequence alignment of the sucrase-isomaltase complex gives insight into potential molecular mechanisms that may be associated with the absence of intestinal sucrase activity, reduced capacity for intestinal starch digestion, and limitations in the efficiency of feed utilization in cattle and sheep. Future research efforts in these areas will aid in our understanding of small intestinal starch digestion and glucose absorption to optimize feeding strategies for increased meat and milk production efficiency.

Estimation of microbial protein synthesis in the rumen of growing lambs based on the purine derivative excretions and the dietary forage-to-concentrate ratio

“…The retention time of concentrate in the rumen is lower than that of fodder, so the effect of fullness that occurs after consuming fodder limits feed consumption [ 6 , 20 , 30 ]. An increased ruminal passage rate of digesta is another reason that affects intestinal digestion and finally increases feed intake [ 20 , 31 , 32 ]. The relative low feed intake of diet 1 can be related to factors such as the woodiness, texture, and physical nature of the feed, the low digestibility of the diet, the decrease in the food passage rate, and the increased time of feed retention in the rumen [ 6 , 19 ].…”

“…The volume of the rumen is one of the factors that limit the optional intake of DM. There are sensitive receptors in the rumen's wall that are stimulated against the stretching and expansion, thus reducing the movement and feed fermentation in the rumen, which will eventually lead to decreased feed consumption [ 20 , 29 , 31 , 32 ]. Increasing DM intake to increase the ratio of concentrate in the diet has often been confirmed in many experiments [ 16 , 17 ].…”

“…The current findings show that increased dietary concentrate levels in diets led to increased final and daily weight gain of lambs, as well as a decreased feed conversion ratio and length of the fattening period [ 6 , 8 , 19 , 28 ]. This may be due to the lack of physical satiety of the animal due to not filling the rumen due to the consumption of concentrate compared to forage [ 31 ].…”

Effects of starch sources varying in particle sizes on ruminal fermentation, nutrient flow, starch digestibility, and lactation performance of dairy cows

“…Moreover, shifting the site of starch digestion from the rumen to the small intestine can potentially provide energetic advantages ( Owens et al, 1998 ; Harmon and Mcleod, 2001 ; Huntington et al, 2006 ). However, the review by Trotta et al (2022) indicates that the absorption of glucose in the small intestine of ruminants is limited.…”