The Nutrition of the Newborn Dairy Calf. II. Effect of Dietary Tryptophan on the Urinary Excretion of Niacin and its Metabolites by Young Dairy Calves

Esh, G. C.; Sutton, T. S.

doi:10.3168/jds.s0022-0302(48)92276-0

Cited by 6 publications

(1 citation statement)

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“…Esh & Sutton (200) found that in the newborn calf, as in other animals, nicorinic acid can arise from tryptophan, and that iV-methyl nicotinamide and other nicotinic acid derivatives are among the forms in which it is excreted. Krupski, Almasy & Ulrich(20l) report that the trouble that results when calves are too quickly changed from milk to an ordinary ration is chiefly due to the negative balance of calcium which results.…”

Section: Nutrition Of Calvesmentioning

confidence: 98%

Section A. Physiology of dairy cattle: Part II. Physiology and biochemistry of rumination

Owen

1951

Journal of Dairy Research

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Studies of rumination have now reached the interesting stage where an attempt at synthesis of empirical data may profitably be made without too much reliance on unsupported hypotheses. The modern researches stimulated by the approach of the recent World War, and actively continued since in many countries, have been a vindication of the inspired guess known as the hypothesis of Zuntz(l), who suggested that the abundant bacterial flora of the rumen were beneficent symbionts rather than mere commensals. This beneficent symbiosis is probably due to the age-long adaptation of ruminants to a diet rich in cellulose, of which a cow may digest more than 60% of its large intake (2). Ruminal bacteria perform many functions of value to their host. They bring about the digestion of cellulose, a process for which the host animal has no appropriate enzymes. They enable the host to cover a not inconsiderable proportion of its amino-acid requirements by means of such simple nitrogen compounds as ammonium salts, glycine or urea(3). Finally, they render the host independent of exogenous supplies of many of the water-soluble and at least one of the fat-soluble vitamins (vitamin K(3)). These are all major advantages which have probably ensured the survival of the ruminant during the geologically recent vicissitudes of the earth's climate. There are also certain minor biochemical advantages in the possession of a rumen with its abundant microflora. Thus phytin, which is abundant in all seeds and which in non-ruminants is rachitogenic, is hydrolysed completely into non-toxic products in the rumen (4). Defatted soyabean (so-called soyabean oilmeal) unless heat-treated to deactivate the antitrypsins which it contains is toxic to the rat (5). The ruminant, however, tolerates it well. Rumination has, of course, its disadvantages too. Thus a ruminant is not as efficient a digester of its preferred diet as is, say, a carnivore, of its preferred diet. With bacterial aid it can digest cellulose which the carnivore can hardly digest at all, but even with bacterial aid its digestion is comparatively slow, and a large fraction of the cellulose normally passes through the alimentary tract undigested. The ruminant's great merit from the economic viewpoint of the animal husbandman is that it digests a diet so rich in cellulose as to be useless to other domestic animals (2,6,7). It will tolerate far more crude fibre (cellulose) in its diet than will chickens, pigs or even rabbits(2). In comparison with the pig or the dog, the ruminant has a large appetite which is a necessary consequence of its large intake of food of low digestibility. To facilitate bacterial digestion the ruminant has a large 'fill'(8), that is to say, the ratio of the weight of food and food residues in the animal at any time to the weight of the animal's living tissues is large. This is due to the delay of the food, during its passage through the animal, in the rumen, the caecum and the colon, in all of which chambers bacterial fermentations are active. Thus the ruminant carries ...

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Section: Nutrition Of Calvesmentioning

confidence: 98%