Your SlideShare is downloading. ×
Physiology (2)
Physiology (2)
Physiology (2)
Physiology (2)
Physiology (2)
Physiology (2)
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Physiology (2)

150

Published on

Published in: Education, Business, Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
150
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
12
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. Physiology Physiology of the cow The cow is a ruminant with four stomachs: • rumen • reticulum • omasum • abomasum The cow is a ruminant with four stomachs. The rumen is the largest, with a volume of 150–200 litres. In the digestion system there are billions of micro-organisms. They help the cow to digest and utilise nutrients in the feed. To achieve good feed utilisation and high milk yield, the bacteria must have optimal conditions. It is the bacteria that digest the feed. Feeding a cow in fact involves feeding the bacteria in her rumen. The process of fermentation takes place in the rumen and the reticulum. Fermentation is when micro-organisms ferment carbohydrates and turn them into volatile fatty acids. This process allows the cow to convert cellulose fibres into energy. Gases are produced within the rumen during fermentation (500–1500 litres per day), 20–40% of which consist of high energy methane. These gases are expelled by belching and this involves considerable energy loss. 1
  • 2. Passage of feedstuffs in the digestion channel Rumination and saliva The cow chews the feedstuff almost without any sorting, which makes her different from other animals such as pigs. After a short period of mastication, when saliva is added, the feed is swallowed in the shape of a bolus. When the cow ruminates, feed returns back to the mouth and is masticated again. It is during the rumination process that the main grinding is done. Why is rumination so important? 1. Mastication. The process of grinding enlarges the surface area of the feedstuff. This greater surface area helps the ruminal micro-organisms and digestive juices to break the feedstuff down. 2. Saliva is added. During mastication, large amounts of saliva are added. A cow produces between 40 and 150 litres of saliva per day, depending on the feed she receives. Roughage has the effect of increasing rumination activity, whereas concentrates reduce it. Saliva has two functions: A. Buffering. Saliva with a pH value of approximately 8.2 has a buffering effect in the rumen. This means that the saliva does not allow acid-producing feedstuffs, such as cereals, molasses, potatoes and fodder beets, to lower the pH value by too much. B. Suppressing foam. Saliva can reduce the risk of bloat as it also has a foamsuppressing effect in the rumen. Salvia production 2
  • 3. Rumen & Reticulum The cow’s rumen is like a large fermentation vat. More than 200 different bacteria, and 20 types of protozoa, help the cow to utilise the nutrients. Feeding a cow in fact involves feeding the bacteria in her rumen. When feed enters the rumen it is placed upon a layer at the rear part. The layer consists of non-digested material with a 15% dry matter content. Bacteria adhere to the feed and gradually erode the digestible material. When the cow ruminates, cuds from the front layer are eructed. Saliva is added in the mouth and through grinding, the surfaces exposed to micro-organisms become larger. The feed particles become smaller as the bacteria work and the rumination process continues. They gradually sink to the bottom of the rumen. The material now has a dry matter content of 5%. The rumen convulses once every minute. The convulsions either belch the ingesta or bring it to the next compartment, depending on the size of the particles. The rumen and reticulum are basically one compartment, but with different functions. Compared to the rumen, the reticulum has a more logistic function: it decides if the ingesta should be brought into the omasum or regurgitated. Circulation of feeds. Rumen pH The ideal rumen pH value is between 6 and 7. The desired micro-organisms are able to operate within this range. If the pH value varies too much, some types of micro-organisms are eliminated, and there is reduced utilisation of the feed. Micro-organisms that digest cellulose (hay, silage, etc.) cannot work with a pH value below 6.0. 3
  • 4. If the cow is fed large amounts of concentrates, her ration should be spread over the day. When the ration is fed only once or twice a day, the result is a large variation in the pH value in the rumen. The figure below shows a schematic description of what happens when concentrates are fed to the cow twice a day, 12 times a day, or in a Total Mixed Ration (TMR). Variation in the rumen pH is reduced when concentrates are fed several times a day instead of twice a day. Omasum . The omasum is the third compartment. It is characterised by the presence of a large number of leaves, which provide a wide absorption surface (about 4–5 m2). This surface absorbs water (30–60% of the water intake) and nutrients such as potassium and sodium. The omasum also prevents the passage of large particles through the digestive system, and may well have functions not yet discovered. Abomasum . The main function of the abomasum is to decompose protein. Gastric juices, produced in abomasum, take care of this. The pH value in this part of the digestive system is 2–3. 4
  • 5. Small intestine When the feed has passed the acid abomasum it enters the small intestine. Here, the pH value increases because the feed is mixed with pancreatic secretion, with a pH value of 8. The main functions of the small intestine are: - to decompose nutrients so that they can be absorbed; and - to absorb amino acids and water via the intestinal villi. Large intestine The large intestine absorbs, recirculates and saves water. 5
  • 6. Small intestine When the feed has passed the acid abomasum it enters the small intestine. Here, the pH value increases because the feed is mixed with pancreatic secretion, with a pH value of 8. The main functions of the small intestine are: - to decompose nutrients so that they can be absorbed; and - to absorb amino acids and water via the intestinal villi. Large intestine The large intestine absorbs, recirculates and saves water. 5

×