Eating and Rumination

Eating food

An ungulates head can be viewed as an advanced grass processing factory, designed to deal with the toughest of foods and prepare it for furthur digestion. Ungulates are herbivores, mainly eating grass and woody vegetation. This diet posses a problem because plant cells have tough thick walls composed of cell wall material known as cellulose, hemicellulose and lignin. These are difficult componenets to break down and digest, mammals do not possess the enzymes to do this, but some mammals with a ruminant digestive system can utilise microbes to break down these substances down for them.

However to aid rumination and also to try to release some of the digestible cell components which may be encased in cellulose, any herbaceous material needs to be thoughly grinded, crushed and chewed. substances such as grass require very fine chewing as they contain relatively little digestible material. By grinding the tough cells can open and the contents become immediately available.

Ungualtes have very specialised high crowned teeth known as hypsodont teeth. Hypsodont teeth are excellant grinders of food. Hypsodont teeth are made up of seperate layers or enamel, dentine and cement. The enamel is considerably tougher than dentine or cement and therefore much more resistant to wear. As the teeth are worn down by constant use, ridges in the tooth are formed, the hard enamel forms grooves. This produces 4 cusps in the ruminants tooth, this gives the enamel grooves more surface area with which to act.
To be able to use its teeth effectively goats and other herbivores have well developed masseter and ptergoid muscles. The pterygoid muscles provide the force to swing the jaw left and right, for example when the animal is chewing the cud. The masseter muscles are found on the sides of the jaw, and are what gives the goat a ‘chunky’ jaw and full cheeks appearance. The masseter helps pull the jaw vertically.

The neck of the goat is quite long and slender, alllowing the goat to hold its head high and watch out or danger. The head is at an angle to the neck and attaches to the neck fairly low down at the base of the skull.

Rumination

All schoolchildren learn that cows have 4 stomachs, but actually all the Artiodactyls apart from pigs, peccaries and hippos ruminate and have more than one stomach. Rumination allows a large quantity of bulk foods to be eaten and processed. For example in the goat there are four stomachs, or more correctly the stomach is divided into four seperate chambers. These are the Rumen, the Reticulum, the Omasum and the Abomasum. The Rumen being much larger than the other three. When the goat eats, food enters the Rumen nad Reticulum, here live many micro-organisms which act to ferment and break down the cellulose and cell walls of plants. The Rumen can be thought of as a washing machine, mixing vegetation with stomach fluids meaning that digestion can occur.

Often the goat will sit resting later and re-gurgitate some food and re-chew it to help its break down. This is known as ‘chewing the cud’. When the pieces are small enough they pass through the Omasum, which acts as a filter keeping large food particles out, and into the Abomasum. The Abomasum is the true stomach and nutrients begin to be absorbed here. From here the food passes into the intestines and eventually out of the body. Most nutrients are absorbed by the small intestine.

Rumination has 2 main advantages:

1) firstly it allows fast feeding. Goats for example can browse quickly, not having to worry about chewing the food too much. They can fill up quickly and finish chewing the cud later. This is useful because it helps the animal avoid predators and minimizes the time spent in dangerous situations or hazardous locations.

2) Also Rumination means ruminants can get the maximum amount of nutrtion from their food. The food is well and truly mashed and enables all the nutrients to be released. This means Ruminants can live in places with very poor food such as coarse grasses but still survive. This can give them the competitive edge over some other species.