The development of digestive function in the pig.

The newborn piglet has a digestive system which is well adapted to a diet of its own dam’s milk, indeed if a sow has a plentiful supply of milk it is very difficult to interest her piglets in any alternative food, certainly for the 1 s t 1-2 weeks of life. Little supplementary food is actually eaten to start with. The piglets sniff the food, nuzzle it and taste it. Food that has been in the pen for some hours does not attract piglets and regular replacement of stale food with fresh is necessary if it is hoped to encourage piglets to learn to eat dry food. Some litters show much more interest than others, but by 2 1 d of age most will be eating appreciable amounts of supplementary food if one has persevered with the presentation of fresh food each day for the previous 1-14 d. For trouble-free rearing of piglets it is desirable to provide supplementary diets which are suited to the digestive capacity of the piglet. To formulate such diets efficiently we need to know as much as possible about the efficiency of the piglet’s digestive system and of any changes in digestive capacity which occur as it gets older. Studies of the reactions of artificially-reared piglets to various combinations of feeds have been valuable in showing up unsuitable ingredients, since such feeds will depress growth or cause scouring and, perhaps, even kill the piglet. Another approach is to study the digestive organs of pigs of various ages and compare histological development, or levels of enzymes and other digestive secretions produced. One can either slaughter the animal for study of the digestive tract, or the digestive system can be cannulated for continuous study of the process of digestion. Another useful way of studying the efficiency of a particular digestive process is to measure the rate of appearance of digestive products in the blood. Conventional digestibility trials have also been valuable in showing up deficiencies in the digestive capacity of the piglet and in demonstrating some of the changes which take place as pigs mature in the over-all efficiency with which