FEEDING STANDARDS AND NUTRIENT REQUIREMENTS OF DIFFERENT CATEGORIES OF LIVESTOCK AND COMPUTATION OF RATIONS
FEEDING STANDARDS
Feedings standards are the tables whichindicates the quantities of nutrients to be fed to the various classes of livestock for different physiological functions like growth, maintenance,
lactation, egg production and wool growth. The nutrient requirements are generally expressed separately for each function or an overall figure for the combined functions may also be
expressed. In the case dairy animals nutrient requirements are generally expressed for the separate body functions but in case of poultry and pigs combined requirements of maintenance
and other body functions are given.
There are two terms which has been used in the feeding standards. One is the nutrient allowance and another is the nutrient requirements. The former gives an extra allowance of nutrient over the requirement which gives a margin of safety whereas latter term gives the requirement for optimum production.
Feeding standards
A. Comparative type
1. Hay standard
2. Scandinavian“feed unit” Standard
B. Digestible- Nutrient system
1. Grouven’s Feeding system
2. Wolff’s feeding standard
3. Wolff’s Lehmann feeding standard
4. Haeckers’s Feeding standard
5. Savage feeding standard
6. Morrison standard
7. National Research Council standard
8. Japanese feeding standard
9. Indian standard
C. Production-value type
1. Kellner-feeding standard
2. Armsby feeding std
3. Agricultural Research Council Standard.
A. COMPARATIVE TYPE
1. Hay standard
In 1810 German scientist Thaer suggested that different feeds should be compared using meadow hay as a unit. This standard provided that 100 lbs. of meadow hay was equal in nutritive value to 91 lbs. of clover hay or 200 lbs. of potatoes, 625 lbs. of mangels. Nothing was known of the chemical value of these feeds and the physiological requirements of the animals. The only measure was the practical feeding experience.
2. Scandinavian “feed unit” standard
In 1884, Professor Fjord formulated the Scandinavian feeding standard. In this system only one factor, namely, the feed unit was taken into account. The value of one pound of common grain such as corn, barley or wheat, is given as one unit value and the value of all other foods is based upon this. According to this standard one feed unit is required for each 150 lbs. of body weight and an additional unit for every three pounds of milk production.
As the grains are of different types in different countries, the feed units should also be different. Hence the Scandinavian units are not applicable in our country unless experiments are conducted here with our own grains.
B. DIGESTIBLE NUTRIENT SYSTEM
1. Grouven’s Feeding standard
In 1859 Grouven, a German chemist published his feeding standard with crude protein, carbohydrates and fat contained in the feed as the basis of the standard. According to this standard a cow weighing 1,000 lbs. should be fed 28.7 lbs. of dry matter containing 2.67 lbs. of crude protein 0.6 lb. of crude fat and 14.55 lbs. of crude carbohydrates.
Very soon after standard of Grouven, Henneberg and Stohaan found that the total nutrient contained in a feed did not from an accurate guide to its value. The proportion of digestible parts varied with different feeds and hence the digestible nutrient would be more valuable. So due to this defect Grouven’s feeding standard is now abandoned.
2. Wolff’s feeding standard
In 1864 Dr.Emil Von Wolff proposed a standard on digestible protein, digestible carbohydrates and digestible fats contained in a feeding stuff. His standard for dairy cows weighing 1,000 lbs. was 24.5 lbs. of dry matter containing 2.5 lbs. of digestible carbohydrates and 0.4 lb. of digestible fats. This as a nutritive ratio 1:5.4. This standard through an improvement over the standard of Grouven, yet it does not consider the quantity and quality of milk produced.
3. Wolff’s Lehmann feeding standard
Dr.V.Lehmann of Berlin modified Wolff’s standard in 1896. Till then Wolff’s standard was in use. He took into account the quantity of milk produced, but he failed to take into account the quality of milk.
4. Haecker’s feeding standard
Haecker an American worker who for the first time considered quality as well as the quality of milk produced in formulating a milk standard. He was also the first to separate requirements for maintenance form the requirements of production. His standard included digestible crude protein, carbohydrates and fats. Later it was expressed in digestible crude protein and total digestible nutrients.
5. Savage feeding standard
Another American scientist Savage came to the conclusion that the Haecker standard was too low especially in protein. He suggested that in case of milking cows at least 24 lbs. of dry matter should be provided for an average cow. The nutritive ratio should not be wider than 1:6 or narrow than 1:4.5. About two-thirds of the dry matter should be from the roughages and one-third from the concentrates. Therefore, the protein requirement was increased about 20 percent above the standard of Haecker.
6. Morrison feeding standard
Morrison F.B. observed that stockmen are spending large sums of money for entirely unnecessary amounts on protein supplement, thus considerably reducing their profits. He therefore, endeavoured to combine in one set of standards what seem in the judgement to be the best guide available in computation of rations for the various classes of stock. These standards were first presented in the 15th edition of “Feeds and Feedings” published in 1915 and where then called “Modified Wolff and Lehmann standard”. They soon came to be known as the “Morrison Feeding Standard”. These standards have expressed in terms of Dry Matter (D.M.), Digestible Protein (D.P.) and Total Digestible Nutrients (T.D.N.)
7. National Research Council (N.R.C.) standard
On animal nutrition of the National Research Council recommended a nutrient allowance. The standard includes digestible protein and total digestible nutrients and also includes the recommended requirements for calcium, phosphorus, carotene and vitamin D for
dairy cattle, beef cattle, pigs, poultry, sheep dogs, horses, laboratory animals etc. It is believed that these N.R.C. reports representing in each case are the pooled judgement of a group of
experts in the field of species in question. Today in a number of countries N.R.C. standards are followed where they use ME for poultry, DE for swine and horses, De, ME and TDN for sheep,
ME, TDN and NEm and NEg for beef cattle and for dairy cattle, values are given for DE, ME, TDN, NEm and NEg for growing animals with additional values as NEl for lactating cows. From
time to time, the NRC revises these feeding standards in keeping with new information and changing feeding practices.
8. Japanese feeding standards for dairy cattle
Maintenance requirements based on live weight raised to the 0.75 power of Maintenance = 37.37 g TDN/kg or 116.3 kcal ME/kg (equivalent to 0.58 lb dig. Protein. 8.1. lb
TDN of 11.4 Mcal ME per 1,000 lb cow). For milk production, nutrient requirements were calculated on the basis of 154 parts dig. Protein per 100 parts milk protein and 1,444 kcal ME per
1,000 kcal milk energy
9. Indian standards
Considering the fact that nutrient needs of livestock and poultry breeds under tropical environments are different from those developed in temperate climate, the Indian
Council of Agricultural Research draw suitable feeding standards for the Indian livestock and poultry.
C. PRODUCTION VALUE TYPE
1. Kellner feeding standard
In 1907 Kellner, a German scientist, investigated a feeding standard based upon “Starch” as the unit of measurement. He took into account not only the digestibility of the feeds as calculated from the amount lost in faeces and urine but also the entire loss from the body including energy expended in digestion and passing the food inside the body (chewing, etc.). For measuring the amount of energy lost from the body as heat, Kellner devised a respiration
apparatus. Here heat in determined indirectly by finding the amount of carbon dioxide gas liberated or by measuring the amount of oxygen gas used up in oxidation which take place in the
body. The animal breathes through an airtight mask placed over its nose and mouth.
According to this system, a 1,000 lbs. animal needs 0.6 lb. of digestible protein and 6.35 lbs. of starch equivalent. This starch equivalent in turn can be converted into energy by a method worked out by Armsby and Kellner.
Any of the feeds the composition of which known be converted to starch equivalent by using the following factors:
Dig Protein X 0.94 = S.E.
Fat from coarse fodder X 2.1 = S.E.
Fat from cereal grain X 2.1 = S.E.
Fat from oil seeds X 2.4 = S.E.
Dig. Carbohydrates and fibre X 1.0 = S.E.
2. Armsby feeding standard
Armsby standard is based on true protein and net energy values. By means of the
respiration calorimeter, Armsby detemined the net energy required for mastication, digestion,
assimilation and also the amount of heat and gases given off through the excretory channels.
Thus after considering the various losses of energy such as in urine, faeces, gases and in the
work of digestion, he was able to estimate the amount of net energy available for productive
purposes. Armsby expresses his standard in two factors, that is true protein and therms of net
energy.
A common criticism of the Armsby standard is that the expense of determining requirements of the animals and the net energy in the various feeds is excessively high. The net energy values of only a very few feeds had actually been determined and most of the values have been computed from the Table of Morrison’s digestible nutrients. Armsby standard is not as widely used as are the standards based on digestible nutrients.
3. Agricultural Research Council (A.R.C.) standard
The nutritive requirement of various livestock in the United Kingdom have been presented in Ministry of Agriculture’s Bulletins. These are prepared by the Technical
Committee of the Agricultural Research Council of Britain. Requirements are set forth in three separate reports dealing with poultry, ruminants and pigs, each of these reports extensive
summaries of the literature upon which the requirements are based. The most attractive feature of the British Feeding Standards is that the unit of energy requirements has been expressed in
terms of Starch equivalent instead of T.D.N. or ME of NE are in Morrison and in N.R.C. standards.
NUTRIENT REQUIREMENTS
Nutritive requirements are the statements of the amount of nutrients required by animals that should support normal function. A rough distinction between requirement and allowance is that the allowance is greater than the requirement by a safety margin designed principally to allow variations in requirement among the individual animals.
Requirements may be expressed in quantities of nutrients or in dietary proportions. Thus the phosphorus requirement of a 50 kg pig might be expressed as ii g. phosphorus per day or as 0.5% phosphorus in the diet. The exact amount of nutrient requirement is used mainly for animals given exact quantities of feed, the expression as per cent of the diet is used for animals feed appetite.
When the standard is set to represent the needs of the average in a population, many will require more than the figure stated, and many will require less the individual stockman does not know whether the average requirements are below or above the requirements of his
animals. For this reason feeding standards should be considered as guides to feeding practice and the stockman should make finer adjustment of food intake to animal performance.
NUTRIENT REQUIREMENT FOR MAINTENANCE
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 giving no 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, animals are forced to draw upon their body reserves to meet their nutrient requirements for maintenance, commonly revealed by a loss in weight and to various other undesirable consequences. The knowledge of this maintenance requirement of farm animals is of utmost importance to find out the total requirements of feed for animals under various conditions such as pregnancy or yielding certain quantity of milk or doing certain amount of work. The procedure involves the summing up of the requirements of each function on top of maintenance requirement. The starting point of finding maintenance requirement is the fasting catabolism.
ENERGY REQUIREMENTS FOR MAINTENANCE
(1) BASAL AND FASTING METABOLISM
The term Basal Metabolism or Basal Metabolic rate refer to the heat production of an animal resting in a thermally neutral environment (temperature range in which environmental temperature does not stimulate normal metabolism, approximately 25C) and in a past-absorptive state (that is after the digestion and absorption of the last food ingested has stopped). During this rest period although the animal will be doing no external or digestive work nor will it have any emotional excitement, still it will carry on a variety of internal processes which are essential to life. These processes include respiration, circulation, maintenance of muscular tonus, production of internal secretions, etc. In the absence of feed, the nutrients required to support these activities must come from the break-down of body tissues itself.
The heat production can be determined by direct calorimetry, or by indirect calorimetry. The conditions of the animals which are essential for measuring metabolic rate are as follow:
1. Good nutritive conditions – this implies that the previous diet of the subject has been adequate, especially as regards to energy and protein. Poor state or previous nutrition tends to decrease of basal neat production.
2. Environmental temperature – temperature or about 25oC specified as one which is above the critical and below the point of hyperthermal rise, thus avoids tissue breakdown.
3. Relaxation on bed prior to and during measurement – by this way the minimum muscular activity can be achieved. This is very difficult for any kind of animal other than man.
4. Post-absorptive state – state when the process or digestion or absorption disappears. It is reached by an overnight starvation in case of human, but for ruminants it may require about three or four days. This condition can hardly be
fulfilled by any ruminants, hence it is measured after a starvation period of about 5 hours. Because of the fact that the last two conditions cannot be fulfilled and a modification is recommended for ruminant animals, hence the term resting metabolism is used in place of basal metabolism.
An animal in the resting state accomplishes little or no work in the physical sense of the word. All of the energy released, even that needed to carry out vital functions of the body is degraded to heat and lost to the environment. Under these circumstances the intensity of energy metabolism can be estimated either by calculating heat production from the exchange of respiratory gases (indirect calorimetry) or by measuring the heat which is lost from the body by radiation, conduction, convection and evaporation (direct calorimetry).
DIRECT CALORIMETRY
This is simple in theory, difficult in practice, sensible heat loss (heat of radiation conduction) from the animal body can be measured with two general types of calorimeters, adiabatic and gradient. The insensible heat (latent heat of water vapourized from the skin and the respiratory passages) is estimated by determining in some way the amount of water vapour added to the air which flows through the calorimeter. For this, rate of air flow and change in humidity is measured.
1. ADIABATIC CALORIMETERS
In this type an animal is confined in a chamber constructed in such a way that heat loss through the walls of the chamber is reduced to near zero. This is attained by a box within a box. When the outer box or wall is electrically heated to the same temperature as the inner wall, heat loss from the inner wall to the outer wall is impossible. Water circulating in a coil in such a chamber absorbs the hear collected by the inner wall; the volume and change in temperature of the water can be used to calculate sensible heat loss from animal body. The construction and operation are complicated and very expensive.
TO BE CONTINUED IN 2ND PART
