In approaching the problem of swine nutrition we must keep in mind the fact that swine production constitutes one of the main items in the agricultural economy of Canada. The status of the industry varies in the different Provinces but by and large revenue from swine contributes substantially to farm spending power and plays a significant part in connection with determining the standard of living which prevails on a considerable percentage of the farms of this Dominion. During our peak year of 1944 swine marketings accounted for a gross revenue of approximately $225,000,000 and, on the basis of our present volume of production and prevailing prices, we may expect a return of around $175,000,000 from this phase of our agriculture. Having in mind the revenue aspect together with the importance of meat supplies in connection with good human nutrition it is clear that the swine business is one that justifies careful study from all angles.

The figures quoted above refer to the gross returns on swine raising. The difference between these figures and the cost of producing the pig crop represents the net return or the actual profit to the farmers on the pig raising enterprise. Continuity of production and stability in the pig business depend- upon net returns and these in turn are dependent upon the relation between selling price per hundredweight and the cost of production per hundredweight. The margin between these figures is never great and in times of depressed prices is very narrow or nonexistent. Since no effective means have been developed to raise the selling price beyond certain levels we are thrown back -on the proposition that the only means which the swine producer has within his own grasp, so far as widening the margin is concerned, is lowering the cost of production.

A pelleted swine feed sample was received from the Veterinary Diagnostic Laboratory, University of Illinois, Urbana, in the autumn of 1986. The farmer who submitted the feed sample reported that boars and sows refused to eat the feed. Subsequently, the sow's milk production decreased and piglets died. Death of some sows also occurred. When a different ration was fed to the remaining boars and sows, they began to eat and their condition improved. Chemical analysis for traditional trichothecene refusal factors by the Animal Disease Laboratory, Centralia, Ill., revealed a low level of vomitoxin in the feed (0.3 ,ug/g). This level of vomitoxin would not account for the refusal activity observed (R. Lambert, unpublished data).

Swine production constitutes an important phase of Canadian agriculture. Revenue from swine contributes substantially to form spending power and plays a significant part in connection with determining the standard of living which prevails on a considerable percentage of the farms of this Dominion. On the basis of our present volume of production, swine marketings for 1947 may be expected to bring in returns in the neighborhood of $150,000,000. It is a business that justifies careful study from all angles.

Introduction
There are a number of challenges facing the pig industry as it becomes more specialized and performance targets increase with the widespread use of UK stock of superior genetic potential. This paper will consider some of the recent nutritional developments, which aim to realise this potential. It will be divided into a number of sections based on the specific age of the animal being considered.

The Piglet Post-weaning
The animals in the immediate post-weaning period have problems. They are weaned between 16- 28 days of age (sometimes earlier), are physiologically and immunologically immature (thus although they can respond to a pathogen attack they have little passive immunity. They are also environmentally and socially stressed. The end result is that they experience digestive upsets, pathologies, dehydration and as a result mortality can be significant.

Introduction
In the recent past, nutrient requirements and feeding management of gestating and lactating gilts and sows have changed dramatically along with genetic improvements although fundamentally, the list of nutrients required by the sows and how they are used have remained much the same. While it has been a common practice to select replacement animals from marketable pigs, gilts now are routinely purchased from breed-specific multiplier herds genetically improved for prolific reproduction and lean meat composition. It is now realized that reproductive performance, as measured by pigs produced per sow per year, has a major effect on profitability for the swine producer. As productivity is greater in sows than gilts, management of the breeding herd must be focused on maintaining sows in the herd as long as possible.