Energy requirement for maintenance,fasting catabolism,energy metabolism of fasting animal

ENERGY REQUIRMENTS FOR MAINTENANCE

Feeding for maintenance

  • Primarily the nutrients in a ration are used for maintaining the life of the animal. Certain amount of energy, protein and other nutrients is required for life sustaining activities of the body such as for the heart to pump blood, for respiration, for the nervous system to maintain its own activity and muscle tone, for temperature regulation, for the general metabolism of most tissues, for active absorption and transport of chemical compounds, for repair of damaged or worn tissues, protein turnover and for the production of hormones and enzymes. If an animal is not fed, the energy, protein and other nutrients required for the above functions will be drawn from the animal’s body reserves of fats, proteins etc. leading to negative energy or protein balance and the animal will lose body weight over a period of time. The purpose feeding animals is to prevent this drain on the animals’ body reserves

Maintenance requirement

  • The maintenance requirement of a nutrient can be defined as the quantity which must be supplied in the diet so that the animal experiences neither net gain nor net loss of the nutrient.

Energy required for maintenance

  • The maintenance energy requirements includes three components,
    • Basal metabolism
    • Energy to maintain the animal’s body temperature
    • Energy for voluntary activity, protein turnover etc.
  • An animal is in a state of maintenance when the amount of nutrients in the feed will maintain the animal in equilibrium i.e., its body composition remains constant and is not growing, not working or not giving any product as milk or mutton or egg.
  • This minimum demand of feed is referred to as the maintenance requirement. If this need is not met, the animals are forced to draw upon their body reserves to meet their nutrient requirements for maintenance, commonly revealed by a loss in weight and other undesirable consequences. The destruction of body tissue is referred to as fasting catabolism.
  • Livestock are fed for production and generally not for maintenance. Maintenance of an animal is an important overhead of the livestock business. A dairy cow weighing 500 kg and producing 20 kg of 4% fat milk daily, uses 37% of its total ME requirement for maintenance, versus 23% at a yield of 40 kg. That is why high milk producing animals are preferred for a profitable dairy enterprise.

Fasting catabolism

  • In the absence of feed, the nutrients required to support the activities essential to life (viz, respiration, circulation, maintenance of muscular tonus, manufacture of internal secretions, etc. ) come from the breakdown of body tissue itself. This destruction of body tissue is referred to as the fasting catabolism and it can be measured in terms of the waste products eliminated through the various paths of excretion. Most of the tissue breakdown occurs to meet the demand of the fasting organism for energy for its vital processes.

Energy metabolism of fasting animal

  • The energy expended in the fasting animal is represented by the fasting animal heat production and this can be measured in the respiration calorimeter (Direct Calorimetry) or can be obtained by one of the methods of indirect calorimetry.
  • Its measurement provides a useful basis of reference for other phases of energy metabolism.
  • The energy used by animals for maintenance is converted into heat and leaves the body as heat.
  • The quantity of heat arising in this way is known as the basal metabolism and measuring this heat produced gives a direct estimate of the net energy the animal should get from its feed to meet the maintenance energy requirement

Methods to determine the energy required for maintenance of animals

  • Measuring basal or fasting metabolic rate
  • Metabolizable energy requirements can also be estimated by conduction short and long term trials with mature, non ­producing animals fed at the maintenance level (if the energy content of their food is known).
  • By conducting feeding trials with different levels of feed intakes and by extrapolation of
  • intake of feed towards zero level of production.
  • Regression methods
  • By conducting slaughter experiments
Last modified: Monday, 6 February 2012, 8:41 AM