Review: Nutritional regulation of intestinal starch and protein assimilation in ruminants

Abstract

Pregastric fermentation along with production practices that are dependent on high-energy diets means ruminants rely heavily on starch and protein assimilation for a substantial portion of their nutrient needs. While the majority of dietary starch may be fermented in the rumen, significant portions can flow to the small intestine. The initial phase of small intestinal digestion requires pancreatic α-amylase. Numerous nutritional factors have been shown to influence pancreatic α-amylase secretion with starch producing negative effects and casein, certain amino acids and dietary energy having positive effects. To date, manipulation of α-amylase secretion has not resulted in substantial changes in digestibility. The second phase of digestion involves the actions of the brush border enzymes sucrase-isomaltase and maltase-glucoamylase. Genetically, ruminants appear to possess these enzymes; however, the absence of measurable sucrase activity and limited adaptation with changes in diet suggests a reduced capacity for this phase of digestion. The final phase of carbohydrate assimilation is glucose transport. Ruminants possess Na+-dependent glucose transport that has been shown to be inducible. Because of the nature of pregastric fermentation, ruminants see a near constant flow of microbial protein to the small intestine. This results in a nutrient supply, which places a high priority on protein digestion and utilization. Comparatively, little research has been conducted describing protein assimilation. Enzymes and processes appear consistent with non-ruminants and are likely not limiting for efficient digestion of most feedstuffs. The mechanisms regulating the nutritional modulation of digestive function in the small intestine are complex and coordinated via the substrate, neural and hormonal effects in the small intestine, pancreas, peripheral tissues and the pituitary—hypothalamic axis. More research is needed in ruminants to help unravel the complexities by which small intestinal digestion is regulated with the aim of developing approaches to enhance and improve the efficiency of small intestinal digestion.

Impact of Green Forages in Spring, in the Steppe Regions of Tiaret “Chehaima and Naima”, on the Fatty Acid Composition of the "Biceps Femoris" Muscle of Lambs

“…Lambs that are feed with concentrate which have exhibited the highest C18: 0 content, has been explained by (Qie et al, 2020), who have found that the concentrated diet increases the C18: 0 content, due to the high saturation of PUFAs; moreover, the total content of SFA reveals a dominance in lambs feed with concentrate, these results are in agreement with those of (Hajji et al, 2016); On the other hand, not only the diet can influence the chemical composition of the meat, but also others factors related to the animal such as breed and age (Erasmus et al, 2017). Concentrated foods are rich in starch, which will increase the intake of FAs by stimulating new ruminal fermentation pathways that increase the saturation of PUFAs (Harmon and Swanson, 2020). Certain supplementary feeds in the ration of small ruminants can modify and reduce the composition of intramuscular SFA and increase those which are unsaturated, by the inclusion of specific oils or oleaginous and marine products (Raes et al, 2004).…”

In situ techniques to predict in vivo digestibility and to evaluate the impact of flint maize processing methods on degradation parameters

“…Regarding the partition of starch digestion, the results showed that a higher amount of starch escapes ruminal fermentation on the DMG diet compared to HMM, RMG, SNAP-80 and SNAP-90-based diets. Studies (Owens et al ., 1986; Harmon and Swanson, 2020) have suggested that the small intestine of ruminants has a limited capacity for starch digestion due to inadequate access and insufficient time of starch granules exposure to enzymes. Therefore, the grain processing method may influence the amount of starch escapes ruminal fermentation and, consequently, the total tract in vivo digestibility.…”

Prenatal and Postnatal Nutrition Influence Pancreatic and Intestinal Carbohydrase Activities of Ruminants

“…Therefore, there could be species-specific responses to maternal nutrient restriction when comparing cattle and sheep. Interestingly, intestinal glucose transport also has been shown to differ between cattle and sheep [13]. However, it should be noted that when Keomanivong et al [36] found a programming response of fetal pancreatic α-amylase, maternal dietary restriction occurred during early or early-to mid-gestation.…”

“…Optimization of digestive enzyme activity could potentially influence nutrient digestibility, whole-animal metabolism, and efficiency. In general, ruminants possess a high capacity to digest protein in the small intestine and absorb end-products (amino acids, di-, and tri-peptides) of small intestinal protein hydrolysis [13]. In contrast, research has suggested that the extent of small intestinal starch digestion is limited in beef cattle (55%) [14] and dairy cattle (60%) [15].…”