Nutrient Requirements of Different Animal Species

The nutrient requirements (quantity and quality) of different animals differ depending on:

• Their species
• Their breed
• Their age
• Their sex
• Their production potential
• Their stage of production
• Whether they are ill or healthy
• The product they produce (whether wool, meat, milk etc.)

These factors will influence the nutrient requirements of animals throughout their lives.

Nutrient Requirements

In general, nutrient requirement tables indicate the nutrient requirements of different age animals for their maintenance requirements as well as for different levels of production. Production indices could include growth, milk production, gestation (pregnancy) or fibre production.

Definition:

A maintenance ration: provides sufficient nutrients for the maintenance of the essential processes of life. The animal will remain in good health without a decrease or increase in body mass. Maintenance requirements are mainly dictated by the body mass of the animal.

A production ration: provides nutrients over and above the maintenance ration to ensure the production of a certain product. Products include growth (meat), milk, young and fibre.

Various “Nutrient Requirement” tables are available (Table 1 of Appendix A contains the NRC Nutrient Requirement table for sheep). These differ mainly in the manner in which the nutrient requirements of the various animals were determined, but are essentially the same. The feeding standards presently used include the:

National Research Council (NRC) USA.

Agricultural Research Council (ARC) Britain.

To interpret the tables, the farmer needs to know how old the animal is, how much it weighs, and its stage of production. For example, the animal in question may be a mature ewe, weighing 60kg, with twins in the first 8 weeks of gestation.

The tables will provide the nutrients (dry material, metabolizable energy, and crude protein) required by the animal at the specific stage of production. The required nutrients may be given as:

• Quantity per animal per day.
• Percentage of the total ration.
• Quantity per kg of the ration.

While reading and interpreting Nutrient Requirement tables is an important skill, a farmer should inherently know that there are certain periods of an animal’s life when improved nutrition is required. Such periods include:

• During mating - In order to obtain a high conception rate or increased multiple offspring the female should be in good condition during the mating season. Flush feeding assists to increase the ovulation rate (multiple ova are released).
• The last six weeks of gestation - The nutritional requirements of the female increase drastically during this period because most of the development of the foetus occurs during this time. Poor nutrition during this period may lead to metabolic disturbances such as ketosis (domsiekte) in the female or the birth of small lambs/calves which are weaker.
• The first eight weeks of lactation - The female has the greatest nutrient requirements during this time since the young is almost totally dependent on the female during this period.
• Active growth stage of the young animal - A high quality feed should be fed to young animals because the requirements for growth are high and the rumen capacity at this stage is still a limiting factor. Poor nutrition during this stage can lead to permanent stunting of the animal. Differences of nearly 20 percent in mature body mass were obtained as a result of differences in nutritional treatment prior to four months of age. Also, the influence of pre- and postnatal treatments was additive. This means that if the mother is fed well in the last few weeks of pregnancy, and the young that are born are strong, then, if the young are also fed well up to weaning, the final result will be even stronger and healthier offspring.

Although it may seem logical that some periods of an animal’s life have lower nutrient requirements, do not be fooled! For example, during the dry period a pregnant dairy cow needs to build up reserves in the form of fat, muscle, tissue and bone for the stressful high production period to follow. Also, although the production of fibre does not necessarily require increased nutrient supply, feed provision/nutrient supply should be constant to avoid breakages or weak areas in the fibre. Since sudden changes in weather can negatively affect feed intake, fibre producing animals should be fed slightly above maintenance requirements to ensure a buffer for sudden stressful periods which may negatively influence fibre quality.

Definition:

Pre- and Postnatal: Pre- and postnatal means before birth and just after birth.

Non-Degradable Protein: Non-degradable proteins are proteins that are not attacked by the micro-organisms of the rumen. Thus, they pass, unaffected into the abomasum and are digested by the acids there.

Nutrient Imbalances

To maintain the health, vigour and productive ability of animals, a farmer needs to manage those factors which can challenge the health of the animal. There are four factors which need to be managed correctly to reduce the chance that diseases will occur.

Poor nutrition: A well-fed animal has a much better chance of fighting off disease and can convert nutrients in excess of maintenance requirements into products.

Stress: Any stress placed on an animal will make it more susceptible to disease (e.g. Pasteurella). Stress includes factors such as parturition, fatigue from walking or being transported long distances, poor housing, excessive cold (especially when combined with damp), excessive heat, high humidity, and dehydration.

Lack of tolerance: Animals in some areas are more tolerant to certain diseases because they have built up a resistance for those factors through being exposed to them for many generations. For example: Goats are browsers, and thus less susceptible to picking up internal parasites from grazing infected pastures. Thus, if you then put a goat onto pastures he will pick up internal parasites more easily.

Lack of immunity: It is important to maintain an animal’s immunity levels. There are two ways, one is allowing the new-born to receive colostrum in the first few days after birth, and the other is through vaccination.

In general, long-term stress causes an increase in the production of cortisol by the adrenal cortex around the kidneys. Persistently elevated levels of cortisol in the blood causes the cells to develop a resistance to the function of insulin (which is to allow the entry of glucose into cells). Thus, glucose cannot enter cells and cannot be utilised by the cells to function normally, since glucose is the basic energy source for life. Elevated cortisol levels due to stress also cause reduction in levels of FSH, LH, growth hormone thus directly impairing reproduction and growth. Also, cortisol induces protein catabolism (breakdown) thus inducing muscle weakness.

Malnutrition

All processes within the body rely on the supply of nutrients. These nutrients include proteins, energy, vitamins, minerals and water in the correct quantities and ratios. If any of these elements are not supplied in the correct quantities, then malnutrition or starvation ensues. In some circumstances, where some nutrients are supplied in lieu (instead of) others the body may be able to manufacture the limiting nutrient. For example: an excess of protein can be converted into energy. However, when this occurs other organs and processes in the body can be negatively affected. For example: when an excess of protein and inefficient energy is supplied, the kidneys are placed under strain to excrete the excess amounts of urea.

Some vitamins, minerals, amino acids and fatty acids are considered “essential” or ‘indispensable” and cannot be manufactured/synthesized by the body and must be ingested from an external source.

Minerals: Mineral imbalances and deficiencies can cause sub-optimal production and reproduction even when there is an abundant feed supply. At least 15 mineral elements are nutritionally essential for ruminants. There are seven major or macro-minerals (Ca, P, K, Na, Cl, Mg and S) and eight trace or micro-minerals (Fe, I, Zn, Cu, Mn, Co, Mo and Se). An excess of Cu, F, Mn, Mo or Se can also cause toxicities. Toxicities can also occur where excess arsenic, lead, cadmium, mercury or aluminium, occurs.

Vitamins: An external supply of all vitamins, except Vitamin K and the B vitamins, are required by animals. In other words, Vitamin K and the B vitamins can be synthesized in the animal body.

Amino acids: Most amino acids necessary for protein synthesis can be synthesized by animals at rates rapid enough to ensure that the animal is not dependent on an external dietary supply. The “non-essential” amino acids include alanine, serine, aspartic acid, glutamic acid, glutamine, proline and hydroxyproline, cysteine, cystine and tyrosine. Sometimes the rates of synthesis are too slow to provide the amino acids in quantities required by the animal. Animals at different ages and in different physiological conditions are synthesizing particular proteins at different rates and this will create a requirement for increased supplies of different types of amino acids. In these cases, amino acids become “essential” because of the physiological stage of the animal. Thus, extra glycine may be required by growing chickens and extra histidine and arginine are required from growth of young. However, some amino acids cannot be produced by synthetic processes in the animal body. Such “essential” amino acids include lysine, phenylalanine, threonine, valine, isoleucine, leucine, methionine and tryptophan.

Fatty acids: Several poly-unsaturated fatty acids, specifically linoleic, linolenic and arachidonic acid must be supplied in the diet. In the rat, dog, mouse, chick, and infant human their absence leads to a cessation of growth, presence of fatty liver, skin lesions, with increased water loss due to increased permeability of skin and abnormalities in pregnancy and lactation.

Metabolic diseases

Disease conditions that manifest themselves due to an imbalance of nutrient ratios are known as metabolic diseases. Some well-known metabolic diseases include:

Milk fever: Characterised by muscle tremors, a staggering gait, and eventually paralysis and death. Occurs in heavily pregnant or lactating animals. It is caused when the calcium absorbed by the digestive tract or extracted from the bone is less than the calcium being supplied to the growing foetus in utero or to the udder for milk production. Can be reversed by supplying calcium borogluconate intravenously.

Pregnancy toxaemia or ketosis (domsiekte): Characterised by the animal being disinterested in her surroundings, is listless, has light muscle tremors, appears to be blind (there is not eye reflex), eventually kneels down and dies. This occurs in heavily pregnant animals. It is caused when the foetus takes up too much room and leaves too little room for the animal to consume the amount of energy necessary for itself and for the growth of the foetuses. This causes the animal to start breaking down stored fat to make up the deficiency in energy. Ketone bodies are formed which lead to blood acidosis. This condition can be reversed with the provision of intravenous glucose.

Grass staggers: Characterised by convulsive seizures where the animal lies down and paddles wildly. Caused by magnesium deficiency. Can be reversed by intravenous administration of magnesium.

Feed Formulation

Click here to view a video that explains basic cattle nutrition.

Click here to view a video that explains what do cattle eat: diet formulation and nutrition.

The cost of feed generally makes up approximately 70% of the costs of a livestock operation. Whether the farmer is producing the feed on the farm or purchasing the feed from outside sources, feed provision to the herd carries a cost. Feed formulation is the process whereby the farmer estimates the nutrient requirements of his animals, and then determines which feeds are required to provide for those requirements at the least possible cost. To do this the farmer will obviously need to know:

• What feeds he currently has available?
• The quantity and quality of the available feeds.
• The nutrient requirements of his/her animals.
• The stage of production and level of production of his/her animals (high milk producers vs. low milk producers or dams carrying singles or dams carrying twins).
• The shortages in nutrients that may occur.
• Which feed resources can be used to supplement the shortages?
• The costs of feed production, mixing, supplementation or outright purchase (including costs of transport and storage).
• The seasonality of feed production and seasonality of feed purchase.

Since feed is the greatest input cost in a livestock operation, one of the main management functions of a livestock farmer is to manage, control and monitor the management of feed to ensure efficient utilisation with little wastage at minimum cost and highest production. Feed management is not a once off event but a daily management task on the livestock operation. To effectively control the costs of this input every farming enterprise should have a well-designed feed flow program in place.

In Nutrient Requirement Tables the Units for Protein and Energy are expressed as follows:

Crude Protein

Crude Protein is an estimate of the percentage of protein that is contained in a feed based on the analysis of N contained therein.

Some tables also present protein as Digestible Protein. That is the part of the ration that is assimilated by the animal when the food is digested. This value will usually be lower than the estimate of Crude protein, since some protein may not be nutritionally available to the animal, although it is present in the feed. Digestible protein is of particular importance to dairy farmers who need more accurate estimates of a feed’s protein content, since milk production is dependent on adequate protein provision.

Energy

Energy values of food are presented as either total digestible nutrients (TDN) or Metabolisable Energy ME. The TDN is expressed as a percentage of the ration. Energy is expressed in (ME) Mega Joules per kilogram of metabolisable energy.

Ration Balancing for Sheep

The following calculation shows how to balance a ration for sheep by utilising low quality roughage and a high protein concentrate. We are interested in formulating a ration for an ewe that is in her first eight weeks of lactation with a single born.

Definition: HPC - HPC stands for High protein concentrate

For the purposes of the calculation presented here a number is provided (in brackets) associated with each value. Let the facilitator help you with that when you do the activity.

The ration should include HPC40 if the preliminary ration does not include at least 60% of a legume roughage (see tip for selecting of preliminary ration).

Click here to download Table 1, The Nutrient Requirements of sheep, provided in Appendix A and Table 2 Composition of Feedstuffs.