Changes in the chemical composition of sow-reared piglets during the 1st month of life

Lawes & Gilbert (1858) recognized over a century ago that proper nutrition of the growing animal requires an understanding of the chemical composition of live-weight gain.They presented very detailed results of chemical analyses of ten farm animalsthree cattle, five sheep and two pigs.Unfortunately, the cattle were not all of one breed, and the sheep were not a strictly comparable series.T h e two pigs slaughtered, however, were litter-mates, killed at different stages during fattening, and Lawes & Gilbert pointed out that using the values for these two animals was 'likely to lead to a pretty trustworthy estimate of the composition of the increase of this particular fattening pig'.Since they also recorded and analysed the food intake of the second pig they were able to calculate the net efficiency of conversion of food nutrients into body tissue, and, for example, were able to show that the fat laid down in the body of the second pig was greatly in excess of that in the food consumed, confirming that fat must have been synthesized from other food components.This classic experiment pointed the way for further work on similar lines.However, in the century that has passed remarkably little work of this type on pigs has been published.There have been considerable advances in analytical techniques, such as the acid hydrolysis method of Venn, McCance & Widdowson (1947) suitable for trace-element studies, and the method of Williams, Curtin, Abraham, Loosli & Maynard (1954) f x amino acid