Elephants are the largest herbivores present on earth. Sixteen to eighteen hours or nearly 80% of an elephant’s day is spent on feeding. Elephants consume grasses, small plants, bushes, fruit, twigs, tree bark and roots. Tree bark is a favourite food source for elephants. These are roughage sources which are rich in calcium. Tusks are used to carve into the trunk and tear off strips of bark. An elephant usually digs up soil to full fill its salt and mineral requirements. Tusks are used to churn the ground. An elephant then places dislodged pieces of soil into its mouth, to obtain nutrients. Frequently these areas result in holes that are several feet deep and vital minerals are made accessible to other animals.
African elephants have hollowed out deep caverns in a volcano mountainside on the Ugandan border, to obtain salt licks and minerals. Hills have been carved by Asian elephants in India and Sumatra searching for salt and minerals. These carved areas in the landscape provide valuable food and shelter resources for a diverse array of native wildlife. Their dung is rich in nutrients are solid food matter which is beneficial to other animals.
Why elephants need to eat so much?
In comparison to other herbivores, the digestive strategy of elephants is characterized by fast ingesta passage, hence a comparatively low digestive efficiency. Digestive efficiency is so low that intact diet items often appear in the faeces sometimes re-ingested by the elephants. Elephants can digest only 40% of what they eat, as consequences nutrients are not properly absorbed. This inefficient digestive system makes the elephants to eat large quantities of food to retain and absorb necessary nutrients for good health. Usually an elephant can eat between 200-250 kg per day. They require large amount of food even though their relative requirement per unit body size is comparatively lower than other herbivores.
Elephant digestive system
One of the most obvious and unique physical features of the elephant is its elongated upper lip and nose forming a muscular trunk capable of reaching from ground level to high branches in its search for food. Unlike the horse, the elephant has no canines or lower incisors and the upper incisors, when present have been modified to form tusks. The grinding teeth do not succeed each other vertically, as in most mammals.
A separate distensible pharyngeal pouch having a sphincter that regulates flow of food and fluid into the esophagus. The lateral movement of the jaws are not pronounced during mastication in elephants. Less volume of the buccal cavity inefficient mastication leads to poor digestibility and hence there is habit of continuous feeding in elephants. Stomach is cylindrical and large intestine has sacculated caecum & colon. Microbial fermentation takes place in caecum and colon. Asian elephant can derive 100% of its maintenance energy from volatile fatty acid (VFA).
The elephant feeds on leaves, bark, stem, twigs, pith, root, fruits and flowers. Elephants graze and browse on the more tender and palatable portions of different plants and trees. Elephants eat between 149 and 169 kg (330-375 lb.) of vegetation daily.
Elephants are pure vegetarian and eat mainly fruits and leaves, such as bamboos, pineapple leave, cucumber, papaya, watermelon, sugarcanes, bananas, coconut leaves and also rice, but we have to steam it before to give it to the elephants. Per day they eat up to 250 kg green leaves and drink about 200 litres of water
In drier habitats Grasses and legumes are more important while palms, vines and a variety of fruits are commonly consumed in moist forests.
On an average elephants require a minimum of 150-200 litres of water each day. Apart from metabolic requirements elephants need water for their natural functions like spraying as well as wallowing for body temperature regulation since the elephant hardly sweats. It is estimated that an average sized adult Asian elephant loses 40 litres of water through urine and 20 litres through the lungs and skin.
Protein and fat
During the wet season, browse intake should have a crude protein content of 13-20% and in the dry season the crude protein value should be 6-18%. The natural diet of elephants is low in fat, found to be 1.2-1.8% of the dry matter intake.
Elephants digest crude fibre with the help of microbes present in the hind gut as well as their digestive system and teeth are adapted to a diet high in fibre content. The elephant being a continuous feeder with its large digestive tract takes feeds low in energy but high in bulk. Both browse and grass are rich in fibre.
The tendency of wild elephants to feed on the bark of certain trees suggested that this might be a source for some minerals. Estimate of Ca requirement for Asian elephants is put at 60g per day. Ca concentration is generally high in legumes and low in grasses, while both P and Na are low in both legumes and grasses. At least 8-9g of calcium is required for the proper growth of the tusks .The deficiency of certain minerals in the elephants leads to reproductive problems, poor growth, emaciation and listlessness, affects growth, reproduction and lactation, leads to abnormal growth, poor appetite, anaemia, pale mucus membrane and irregular pulse.
Vitamins are a group of organic compounds essential for normal maintenance, growth and reproductive functions apart from protein, fat, carbohydrates and minerals. Many herbivores all their required B complex vitamins.
An adult Asiatic elephant requires around 2.5-6 tones feed. They needs about 18g DM, 6g DCP, 237 Kcal ME and 5g Ca per kg metabolic body size or dietary 8-10% CP, 0.3% Ca, 0.2% P, 50ppm Fe, 50ppm Zn and 10ppm Cu.
Daily water requirement varies from 68.4-98.8 litre (18 to 26 gal.) but may consume up to 152 litre (40 gal.). An adult male elephant can drink up to 212 litre (55 gal.) of water in less than five minutes.
These large requirements are due to their poor utilisation of foods. Nearly 60-65% of food intake remains undigested.
PhD Scholar, Division of Animal Nutrition, Indian Veterinary Research Institute, Izatnagar, UP-243122
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