Animal Health and Nutrition

Farm animal products like meat, milk, wool, mohair, animal skins and eggs consist mostly of protein. Protein is built from different amino acids and to synthesise the proteins out of the amino acids, energy is needed in the process.

The amino acids and energy needed must be obtained from the food intake of the animal. The nutrients in the food must first be digested by the digestive system and the digested nutrients transported to the area where the nutrients (amino acids or energy) is needed by the circulatory system. In the process, other systems of the body, like the endocrine-, urinary- and many other systems might take part in the production process of the products produced by the animal.

The anatomical systems of the body are therefore not only responsible for the maintenance of the body but are also needed for the production of most farm products.

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 cause 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: Animals require an external supply of all vitamins, except Vitamin K and the B vitamins. 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 hyroxyproline, 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, growing chickens may require extra glycine and extra histidine and arginine are required from growth of young. However, synthetic processes in the animal body cannot produce some amino acids. 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 compounds.