IV. Carbohydrates, Digestion and Absorption Flashcards
What processes are involved in the digestion or fermentation of carbohydrates in monogastric and ruminant animals?
Monogastric animals (e.g., pigs, chickens): Carbohydrate digestion occurs primarily in the small intestine, where enzymes break down complex carbohydrates (like starch) into simpler sugars (like glucose) that can be absorbed into the bloodstream.
Ruminant animals (e.g., cows, sheep): Carbohydrates are fermented by microbes in the rumen (a specialized stomach chamber) into volatile fatty acids (VFAs), which are then absorbed and used as energy.
Define Amylase.
An enzyme that breaks down starch into simpler sugars like maltose and dextrins. Amylase is produced by the pancreas and secreted into the small intestine in monogastrics, and is not secreted by ruminants.
Define Volatile Fatty Acids (VFAs).
VFAs are short-chain fatty acids produced by the fermentation of carbohydrates by microbes in the rumen.
The primary VFAs are acetic acid, propionic acid, and butyric acid, which serve as key energy sources for ruminants.
Where does the primary digestion of carbohydrates occur in monogastrics, and what enzymes are involved?
Site: The small intestine is the primary site of carbohydrate digestion.
Enzymes involved: Pancreatic amylase starts breaking down starch into maltose and dextrins. Disaccharidases on the intestinal brush border, such as maltase, sucrase, and lactase, then break down these products into monosaccharides like glucose, fructose, and galactose, which are absorbed into the bloodstream.
What are the end products of carbohydrate digestion in monogastrics?
The main end product is glucose, which is absorbed into the bloodstream and used as a primary energy source. Other simple sugars like fructose and galactose are also produced and absorbed.
Name and describe the function of the main enzymes involved in carbohydrate digestion in monogastrics.
Amylase: Breaks down starch into maltose and dextrins.
How do ruminants digest carbohydrates differently from monogastrics?
Carbohydrates are primarily fermented by microbes in the rumen rather than being digested by enzymes in the small intestine.
The microbes break down carbohydrates into volatile fatty acids (VFAs), which are absorbed through the rumen wall and used as energy. Monosaccharides are also produced but are less significant compared to VFAs.
What are the three major VFAs produced in the rumen, and what are their roles?
Acetic acid (C2): Has 2 carbon atoms. It is primarily used for fat synthesis in the body and contributes to energy production.
Propionic acid (C3): Has 3 carbon atoms. It is the main precursor for glucose synthesis in the liver, which is important for maintaining blood sugar levels.
Butyric acid (C4): Has 4 carbon atoms. It is converted into energy sources like ketone bodies, which are used for energy by various tissues.
What factors can affect rumen fermentation and VFA production in ruminants?
Forage vs. Concentrates: The type of feed influences the types of VFAs produced.
High Forage (e.g., grass, hay): Increases acetic acid (C2), which is used for making fats.
High Concentrates (e.g., grains): Increases propionic acid (C3), which helps make glucose.
Feed Processing: How the feed is prepared affects fermentation.
Ground or Pelleted Feed: Can improve fermentation efficiency compared to whole feed.
Additives and Species: Additives and the type of animal can change the microbes in the rumen, which affects VFA production.
Additives: Such as probiotics, can boost certain microbes.
Species Differences: Different ruminants have unique microbial communities affecting fermentation.
What is the typical VFA molar ratio with a roughage diet versus a concentrate-rich diet?
Roughage diet: 65% acetic acid, 25% propionic acid, 10% butyric acid.
Concentrate-rich diet: 50% acetic acid, 40% propionic acid, 10% butyric acid.
What causes rumen acidosis in ruminants, and what are its consequences?
Rumen acidosis occurs when animals are fed high-grain-rich diets or when there is a sudden dietary shift from pasture to feedlot conditions, leading to an overproduction of lactic acid.
Consequences: It can lead to decreased feed intake, reduced milk production, laminitis, and in severe cases, death.
What are the end products of carbohydrate digestion in monogastrics?
Mainly glucose, along with other monosaccharides like fructose and galactose.
Why can high-NSP diets cause issues in poultry?
High levels of nonstarch polysaccharides (NSPs) in poultry diets (e.g., from barley or rye) can increase the viscosity of the digesta, leading to poor nutrient absorption, sticky feces, dirty eggs, and digestive problems like diarrhea.
What are the end products of carbohydrate digestion in ruminants?
Mainly volatile fatty acids (VFAs) like acetic acid, propionic acid, and butyric acid, along with some monosaccharides.
