(Animal Nutrition)--Unit 6. Energy

 

Unit 6.

Energy

The amount of energy locked up by the bonds that hold a molecule of feed stuff together cannot be determined by direct means. However, the amount of heat energy given off or absorbed when a molecules is formed or decomposed during a chemical reaction is determined by a metal instrument, which is called a bomb calorimeter.

Net Energy System

By the use of respiration apparatus Kellner and Zuntz determined the losses of energy for mastication, digestion and assimilation. Armsby not only determine the energy required for mastication, digestion and assimilation of feed, but he also determined the amount of heat and gases given off by the body in respiration calorimeter.

Partitioning of Energy

The energy value of feeds may be considered under the following heads:

Gross Energy

The energy given out in the form of heat when it is completely burned down to its ultimate oxidation product namely CO₂ and H₂O. The fat contains twice as much heat as the same quantity of carbohydrate.

Digestible Energy      

All the heat produced by burning food in the bomb calorimeter is, however, not utilized in the animal body because food is not digested completely. The amount of energy excreted in the faeces from subtracted from gross energy gives the digestible energy of the feed.

Metabolizable Energy

In addition to the loss of energy in the faces, energy is also lost in urine and due to the rumen fermentation. When the losses in urine, feces combustible gases are subtracted from the gross energy intake, Metabolizable energy of feed is estimated.

Net Energy

Net energy is more scientifically sound for expressing energy requirements and energy value of feed. To arrive at the net energy calculation, energy spent in the work of digestion is also deducted. It is obvious that the movement of jaw in chewing a dry fibrous need energy. The secretion of digestive juices and microbial breakdown of the crude fiber also required energy. The heat thus produced is known as heat increment of the total effect namely chewing, mastication, absorption etc. The efficiency of energy use for maintenance, Pregnancy and lactation

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