DIFFERENT ANIMALS HAVE DIFFERING NEEDS
Every species, and individual, animal requires different nutrition and in order to provide them with the most optimal diet we must understand feed analysis.
Nutritional analysis usually tells us the amount of protein, carbohydrates, fat, fibre and moisture. These may vary in amount due to the species, age, health, activity, reproduction and environmental condition. Proximate analysis through laboratory testing is a common method for analysing the nutrient content of feed. A series of chemical tests are carried out and provides the percentage of protein, fat, moisture, fibre and soluble carbohydrates. It does not provide information on vitamins, minerals, essential fatty acids or amino acids.
CONCERNS ABOUT ANIMAL FEEDING
Diseases carried in feeds
Disease can be transmitted to and between animals (including to humans) from organisms or contaminants in animal feed. This is cause for concern both in the public health and animal welfare arenas. Some examples of these issues are:
- Salmonella, a bacterium, sometimes transmitted from manures or dirty water/equipment coming into contact with feed.
- Listeria, a bacterium, that can be found in poorly stored feed.
- Foot and Mouth disease, caused by a virus, found in contaminated feed or dirty equipment.
- Diseases such as Bovine spongiform encephalopathy (BSE), believed to be from prions present in animal products fed to cattle and then later ingested by humans
- Measles disease in cattle usually from feed contaminated by human faeces
- Aujeszky's disease, caused by a virus, that is infectious in many animals
Hygiene and health controls in many countries have been instituted to deal with these types of diseases. The feeding of swill, unprocessed animal products or of animal proteins to livestock is banned in many countries to help prevent outbreaks of diseases such as BSE and Aujeszky's disease.
Anti-nutritional factors in feed
There are several advances in addressing some problems associated with unfavourable components of feed (anti-nutritional factors). There is work on reducing tannin content of some tree and shrub material used for feed. Addition of essential oils may sometimes be beneficial for ruminants and the use of other additives such as enzymes can lead to beneficial effects on livestock performance.
Environmental concerns
In many countries, there is the desire or the legal obligation to reduce greenhouse gas emissions. Improved feeding practices (such as increased amounts of concentrates or improved pasture quality) can help reduce methane emissions. Many specific agents and dietary additives have been proposed to reduce methane emissions, including some antibiotics, and compounds that inhibit methane production such as yeast cultures. This is an on-going field of research to determine whether these have any practical benefits.
It has also been estimated that up to one third of arable land is used for livestock feed production. This may be associated with land clearing, use of chemicals to grow feed, excessive consumption of water resources, reduction of natural habitat for wildlife and increased erosion. Improved environmental practices including sustainable ways of producing feed are therefore being developed including pasture management, responsible/minimal use of chemicals, better monitoring and management systems for water use and maintaining ground cover by rotational grazing.
ACCESSORY ORGANS OF THE DIGESTIVE SYSTEM
Lets now look at the accessory organs found along the digestive tracts of both ruminants and non-ruminants.
Salivary Glands
The function of the salivary glands is to produce fluid which pours into the mouth while the animal is eating. This fluid assists in the chewing process so that food is more easily broken down. It also makes the bolus (ball of food) more slippery so that it passes easily down the oesophagus.
There are three pairs of salivary glands:
- parotid gland : this means "ear" - the parotid gland is situated in front of the ear;
- mandibular gland : this means "jaw" - this gland is found in the lower jaw; and
- sub lingual gland : this means "of the tongue" - this gland is found under the tongue
Salivary glands produce two types of fluid. One is a thin, clear, watery fluid and the other is a thick, sticky fluid called mucous. These two fluids are mixed together to produce saliva (which is the liquid in the mouth).
The other important function of the salivary glands is to produce an enzyme called ptyalin (the p is not pronounced). This enzyme starts the process of digestion in the mouth by turning some of the starch in the food that was eaten to sugar. It is important because it starts the chemical process of digestion as opposed to the mechanical process which is carried out by the grinding action of the teeth.
Pancreas
The pancreas is situated below the stomach but above the part of the small intestine called the duodenum. The pancreas is made up of two types of glands - exocrine glands and endocrine glands. Exocrine glands make up the largest part of the pancreas.
An endocrine gland has no duct system - it pours its secretions directly into blood vessels which run throughout the pancreas. Exocrine glands, in contrast, pour their secretions into ducts - these join up and lead into the pancreatic duct and so into the duodenum.
The function of the pancreas is to produce two chemicals:
The enzymes produced are: trypsin, chymotrypsin, carbozypeptidase, lipase, and amylase. You do not have to remember the spelling of these complicated names. Just remember that they are enzymes and their job is to assist in the breakdown of complex nutrients such as starches, sugars, oils, and fats into the simple sugar glucose which is the end product of digestion. Glucose is the fuel for the body.
The endocrine part of the pancreas produces two hormones: insulin and glucagon. Their task is to regulate the breakdown of the complex nutrients into simpler compounds. They decide how much is broken down and how quickly.
The pancreas pours its secretions into the duodenum at a point very close to the point where the bile duct (leading from the liver) also joins the duodenum. This is important because it means that the secretions from both organs can work together in the process of digestion. Between them the two hormones, insulin and glucagon, control the levels of glucose in the blood. Glucose levels in the blood are raised by glucagon and lowered by insulin.
Although insulin performs several functions, its main task is to pass glucose across the cell membranes (or walls) into the cells where it can be further broken down and converted into energy. If there is a shortage of insulin in the body, glucose remains in the blood and builds up - it cannot be utilised by the body and some is wasted. This condition in humans is known as diabetes and if a person is a severe diabetic, they have to inject themselves with insulin every day and avoid eating sugary foods which are easily converted into glucose.
Glucagon controls how much and how fast sugar (that is stored in the liver) is released into the bloodstream. When the body needs more fuel, glucagon works to increase the glucose levels in the blood. Insulin and glucagon work together to maintain the ideal level of glucose in the blood.
