Cattle, as ruminants, have a digestive system (especially the rumen) that is evolutionarily adapted to high-fiber, low-starch roughage, such as grass and straw. However, "high concentrate" usually refers to feed with a high starch content (such as corn, barley, bran, etc., with a starch content of over 50%) and a low crude fiber content (typically less than 18%). The "high energy, low fiber" characteristic of this type of feed conflicts fundamentally with the natural digestive logic of the rumen of cattle. The core function of the rumen is to decompose crude fibers through microbial fermentation, rather than efficiently processing large amounts of starch.
Undigested starch enters the hindgut, causing osmotic diarrhea
1. Decrease in rumen starch digestion efficiency: Under normal circumstances, the rumen can digest 60% - 80% of the starch. However, feeding high-quality concentrates can lead to imbalance in the rumen microecology, resulting in a decrease in rumen digestion efficiency. A large amount of undigested starch will pass through the rumen and enter the small intestine.
2. Limited starch digestion capacity of the small intestine: In beef cattle, the digestion of starch in the small intestine mainly relies on pancreatic amylase, and its digestive capacity is limited. The starch that is not absorbed by the small intestine will further enter the large intestine (cecum and colon).
3. Post-intestinal fermentation and increased osmotic pressure: Microorganisms in the large intestine (such as Escherichia coli and lactic acid bacteria) will ferment the remaining starch, producing a large amount of lactic acid, volatile fatty acids and gases, which leads to a sharp increase in osmotic pressure within the large intestine (an increase in solute concentration).
4. Water attraction and the formation of diarrhea: According to the principle of osmotic pressure, a high osmotic pressure in the intestinal cavity will draw water from the blood vessels in the intestinal wall into the intestinal cavity, resulting in a significant increase in the water content of the intestinal contents, thereby causing osmotic diarrhea. This is manifested as loose and watery stools.
Disorder of intestinal flora and mucosal injury
1.Disruption of microbial balance: Abnormal metabolites (such as lactic acid and toxins) produced by the abnormal metabolism of high-quality feed passing through the rumen and entering the intestine can disrupt the balance of intestinal bacteria, leading to the rapid proliferation of harmful bacteria (such as Escherichia coli and Salmonella) and inhibiting beneficial bacteria (such as Bifidobacterium).
2. Mucosal irritation and increased secretion: The toxins produced by harmful bacteria (such as endotoxins) will stimulate the intestinal mucosa, causing congestion, edema and increased secretion.
3. Accelerated intestinal peristalsis: The intestinal peristalsis speeds up due to increased stimulation. The time that food stays in the intestines is shortened, further reducing the efficiency of nutrient absorption and exacerbating diarrhea.
Other factors: The cumulative effect that exacerbates diarrhea
The impact of insufficient crude fiber: When there is a lack of crude fiber in high-quality feed, it will cause the intestinal peristalsis to slow down (crude fiber can stimulate intestinal peristalsis), prolong the retention time of food, and increase the risk of abnormal fermentation. At the same time, the feces become soft due to the lack of fiber support.
Summary
The core logic behind the occurrence of diarrhea in beef cattle due to high concentrate feed is as follows: High starch disrupts the rumen microecological balance → Undigested substances enter the intestinal tract → Abnormal posterior intestinal fermentation and increased osmotic pressure → Disruption of intestinal function → Diarrhea. This process involves the interaction of multiple links, ultimately leading to symptoms such as soft feces or diarrhea in beef cattle.
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