Feeding Standards and Measures of Feed Energy | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Understanding Feeding Standards and Measures of Feed Energy

• Feeding standards are essentially tables that outline the nutritional value of feed and the food requirements of animals for different purposes like growth, fattening, and lactation.
• These standards also provide essential data for designing various nutrition experiments, especially those that necessitate a basic ration rich in all nutrients except the one under study.
• It is crucial to express the nutritive value of rations in common terms, such as energy of nutrients, to facilitate comparison and analysis for different purposes.

Expressing Nutritive Value of Feeds

• Various methods have been employed to express the nutritive value of feeds, including energy, total digestible nutrients, and digestible proteins.
• For instance, Armsby in America and Kellner in Germany introduced standards that converted food constituents into energy or starch equivalents.
• While all food constituents can be represented in terms of energy, it is essential to ensure an adequate protein supply for maintenance and production purposes.

Importance of Digestible Proteins and Total Digestible Nutrients

• Expressing food and food requirements in terms of 'Digestible Proteins' and 'Total Digestible Nutrients' is crucial for effective nutritional assessment.
• Any standard chosen should ensure that the food supplies both the total amount of energy and a minimum required protein level for maintenance and production needs.

Types of Feeding Standards

• Armsby's energy standard
• Kellner's starch values or starch equivalents
• Standards based on total digestible nutrients and digestible proteins

Food Energy Measures

• Total Digestible Nutrients
• Digestible Energy
• Metabolizable Energy
• Physiological Fuel Values
• Net Energy
• Starch Values

Total Digestible Nutrients (TDN):

• TDN represents the actual value of food after deducting losses in feces, urine, combustible gases, and heat elimination.
• Determining the digestibility of nutrients is crucial to understanding the true value of food.
• TDN helps in comparing different feeds by eliminating fecal losses, making them comparable.
• The digestion coefficients for common feeding stuffs are readily available.

Relationship between TDN and Net Energy:

• 1 pound of TDN in maize equals 1 Therm net energy.
• 1 pound of TDN in good hay equals 0.75 Therm net energy.
• 1 pound of TDN in poor roughage equals 0.5 Therm net energy.
• Poor quality roughages have lower energy values due to poor digestibility.

Measuring Food Energy:

• Gross Energy
• Digested Energy
• Metabolizable Energy
• Fecal Energy
• Energy of Urine and Combustible Gases
• Heat Loss
• Net Energy

Relationship between Various Measures of Food Energy:

• The different measures of food energy are expressed in calories, kilocalories, or therms, depending on the unit of measurement.
• Relationships between different measures such as Gross Energy, Digested Energy, Metabolizable Energy, and Net Energy are essential for understanding the energy values of food.

Digestible Energy:

• Digestible energy is the energy obtained after subtracting the energy lost during digestion.
• It can be calculated in two main ways:
  (i) By determining the gross calories in the food and feces and then calculating the digested energy.
  (ii) By using the caloric factors of digested nutrients - carbohydrates (4.1), proteins (5.65), and fat (9.4).
• No specific feeding standard has been established based on digested energy.

Metabolizable Energy:

• Metabolizable energy accounts for losses occurring in urine and combustible gases.
• It is considered a more accurate measure than digested energy but doesn't include heat losses from the animal's body.
• Measuring metabolizable energy requires specialized techniques and equipment, limiting its availability for many feeds.

Physiological Fuel Values:

• Physiological fuel values are similar to metabolizable energy for humans but may not be suitable for other species due to varying digestive and metabolic conditions.

Net Energy:

• Net energy is the energy that is entirely useful to the body, accounting for all metabolic losses.
• It is a more precise measure of energy conversion, considering the energy used in producing meat, milk, eggs, or work.
• Net energy values are not ideal for colder climates and are based on data obtained in warm environments.
• While theoretically superior in accounting for all losses, determining net energy values is expensive and challenging, limiting their availability to only a few feeds.