'In a previous article [note: ‘”A Study of Commercial Dog Foods,” Vet. Med., Vol. XXVII, 5, 204.’] attention was called to the chemical analysis of several of the leading brands of dog foods. Attention is now called to their biological value.

Feeding knowledge can be divided into three periods.

1. The chemical period.

2. The energy period.

3. The biological period.

It is in the latter period that we are at present. We are more concerned now with the protein after digestion than the protein as such. We no longer believe that vegetable and animal proteins are of equal value nor that proteins from all animal sources are adequate and equal. We now are concerned more with unseen vitamins, minerals and amino acids than with chemical analysis.

The term “balanced food” is rather loosely used when applied to the average dog food. The requirements for growth and maintenance, particularly maintenance, during gestation and lactation are not adequately met in many of the commercial dog foods which came under the writer’s attention. We can expect little else while the stress is placed on chemical analysis and biological values are ignored. It is pertinent to recall to memory the position diet holds in relation to health and disease. In man or beast its adequacy or deficiency may well be observed from birth to death. It is immutable that a food is no better balanced than its constituents permit and no more adequate than its source.’ (324)

'Proteins, vitamins, and minerals play an important role in the reproductive cycle. Some experiments by Dagg's [sic] [note: 'Daggs, C.G., Jour. Nutrition, 4:443.'] employing four proteins, muscle meat, liver, egg and kidney, and used in connection with diets otherwise inadequate, proves the influence of protein on the reproductive cycle in dogs. The number of young born. their growth, maternal nitrogen balance, as well as blood and urine analysis and volume and analysis of the milk, were studied. No young were born on the kidney diet. It appears that a more favourable nitrogen balance was obtained on the liver diet than on either the egg or muscle meat diets. Liver, likewise, favoured a higher quantity of milk with a greater fat content than either of the other proteins studied. Pups suckling the liver fed dogs grew faster than on the other protein diets. The nutritive importance of manganese has recently [326-327] come in for study in both plants and animals.It has been found that diets otherwise adequate but lacking in this element were productive to testicular degeneration in the males. In the females the estrus cycle was not interfered with, but htere was a deficient lactation. In the studies of the writer degeneration of the testes has been observed in several instances.' (326-327)