Quoted by 'Cooked Food Best for Dogs, Tests Prove', The Edinburg Daily Courier (1st Aug. 1932), p. 2.
Description:

'Raw meat, sometimes advocated for dogs simply because It was their "natural" food In the wild state, has no greater food value and is [illeg.] harder to digest than meat which is lightly cooked, according to Dr. W.M Clifford, famous British nutritionist. In an exhaustive series of tests Dr. Clifford proved that cooking at the level of a "rare" roast destroys the anti-enzyinic compounds in the meat, while no food value is lost to cause the hardening effect of [illeg.] proteins has hardly come into play. The experiments have aroused wide attention, the Journal of the American Medical Association declaring that "now the raw meat propaganda is meeting with experimental rebuff."'

 

Relevant passages from 'Cookery and Digestibility':

'Cookery has become an important feature of the modern dietary regimen. As the application of heat to foods represents an important distinction between thefeeding habits of man and those of animals, one may properly ask for an explanation of the human peculiarity. Indeed, the "back to nature" cults in many instances insist on the preference for raw foods...

... However, there are manysigns of incipient revolt against the widespread prevalence of the use of high temperatures in the processing of foods. This reaction is based in part on the newer knowledge of valuable properties or constituents of foods, notably the vitamins, which are in some instances [2038-2039] subject to deterioration when they are exposed to heat and other destructive environmental conditions. The fear of loss of undescribed essential properties of foods has produced some enthusiasm for raw foods. Probably there is much physiologic wisdom in such an attitude. However, justice demands a balancing of all the reputed advantages and disadvantages of heat cookery in the formulation of final judgments...

Some of the debated questions involve the compara¬tive digestibility of raw and of cooked foods...

And now the raw meat propaganda is meeting with experimental rebuff. Against the bold generalization, like that of Hutchison, [note: 'Hutchison, Robert: Food and Principles of Dietetics, New York, William Wood & Company, p. 396.'] that the digestibility of animal foods is diminished rather than increased by cooking, may be pitted the tests of Clifford [note: 'Clifford, W. M.: The Effect of Cooking on the Digestibility of Meat, Biochem. J. 24:1728, 1930.'] at King's College of Household Science in London. These show that, taking rapidity of hydrolysis as a criterion, meat when raw is in the least digestible condition. The most rapidly digested meat is that which is roasted or grilled until it is just red inside with a moist surface when cut. This point probably coincides with that at which the antienzymic properties of animal tissues are destroyed, while the hardening effect of heat on proteins has hardly come into play. Clifford adds that, if the heating is carried beyond this point and the meat is definitely overcooked, the rate of digestion is slowed but, unless the meat is actually carbonized, it even then appears to be more rapidly digested than raw meat. The least rapidly digested form of cooked meat found in these experiments is an overboiled mince; the most rapidly, an underdone roast. It would therefore seem that, for people with weak digestive powers or for young children, the ideal form in which to administer animal protein is as underdone roast beef minced after cooking. The mince that comes from an ordinary household machine as a moist paste is palatable. Clifford also found that the decrease of digestibility in overcooked meat appears to be due to hardening and drying of the protein since, if underdone roast or grilled meat is rewarmed but not overcooked, its digestion rate is unaltered; but if it is reheated until it is quite overcooked, the rate is slowed. This is in accordance with general opinion among cookery teachers who recommend the rewarming of meat but condemn recooking... whatever their inherent virtues such as richness in sensitive vitamins, digestion of their proteins is not universally enhanced when they happen to be consumed in nature's state.' (2038-2039)