|SMITH, WYATT - South Dakota State University|
|BRAKE, DEREK - South Dakota State University|
|FOOTE, ANDREW - Former ARS Employee|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2020
Publication Date: 9/1/2020
Citation: Smith, W.N., Brake, D.W., Lindholm-Perry, A.K., Oliver, W.T., Freetly, H.C., Foote, A.P. 2020. Associations of mucosal disaccharidase kinetics and expression in the jejunum of steers with divergent average daily gain. Journal of Animal Science. 98(9):1-6. https://doi.org/10.1093/jas/skaa285.
Interpretive Summary: The gastrointestinal tract of beef cattle has important roles in the digestion and assimilation of feedstuffs. Shifting starch digestion from the rumen to the small intestine can improve the efficiency of nutrient utilization. Altering site of digestion can be accomplished by processing the grain. However, previous research has indicated that expression of enzymes involved in starch digestion may be increased in more efficient cattle. The goal of this study was to determine if the activity and kinetics of isomaltase and maltase differed in cattle with average feed intake and relatively fast or slow growth rates. The activity and kinetics of the isomaltase and maltase were not different between the two groups. Additionally, the expression of the genes encoding these enzymes were not different. While digestion of nutrients is important for efficient nutrient utilization, these results indicate the activity of enzymes breaking down isomaltase and maltase in the small intestine may not be an important contributor to differences in growth rates of cattle in the feedlot.
Technical Abstract: The objective of this study was to quantify the differences in the activity of jejunal maltase and isomaltase between 2 groups of steers with average dry matter intake (DMI) and differing average daily gain (ADG). Dry matter intake and ADG were measured in crossbred steers (n = 69; initial body weight = 456 ± 5.0 kg) consuming a finishing diet containing 67.8% dry-rolled corn, 20.0% wet distillers grains with solubles, 8.0% alfalfa hay, and 4.2% vitamin/mineral supplement on a dry matter basis for 84 days. Jejunal mucosal samples were collected from 8 steers with the greatest (high) or least (low) ADG and average DMI (± 0.55 standard deviation). Homogenates of jejunal mucosa were incubated with increasing amounts of maltose and isomaltose to determine the disaccharidase kinetics. Total mucosal protein concentration (mg protein/g tissue; P = 0.45) of the mucosa and small intestinal weights (P = 0.69) did not differ between the groups. Neither the Km of isomaltase (P = 0.15) or maltase (P = 0.21) differed between groups. The isomaltase Vmax expressed per gram of protein tended to differ (P = 0.10) between groups of steers but did not differ (P = 0.13) when expressed on a tissue basis. Similarly, neither the maltase Vmax expressed per gram of protein (P = 0.31) or tissue (P = 0.32) differed between groups. While previous studies have indicated that disaccharidase expression is associated with differences in ADG, data presented here indicate that differences in enzyme activity at the end of the finishing period are minimal.