The absorption of ammonia from the rumen of the sheep

McDonald, I.

doi:10.1042/bj0420584

Cited by 197 publications

(69 citation statements)

References 9 publications

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“…The total phosphate concentration of saliva in most species is about twice that of the plasma (Burgen & Emmelin, 1961), whereas in the horse, the plasma level of phosphate was nearly 6 times that of the saliva (Alexander, 1962). The level of urea in horse saliva resembled that in sheep (Macdonald, 1948), in which species it contributes to the animal's protein being synthesized by the rumen organisms into bacterial protein which is then digested by the sheep. It is possible that the salivary urea might be used by the organisms involved in the gastric fermentation in the horse as a source of non-protein nitrogen to form bacterial protein.…”

Section: Discussionmentioning

confidence: 99%

A study of parotid salivation in the horse

Alexander¹

1966

The Journal of Physiology

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1. Saliva flowed from the horse's parotid duct only during mastication. 2. The surface‐active local anaesthetic administered by mouth inhibited salivary secretion. 3. Salivary secretion was stimulated by pilocarpine and inhibited by atropine. 4. The volume and composition of saliva secreted in 24 hr from one parotid duct was determined. 5. The concentration of sodium, potassium, calcium, chloride and bicarbonate depended upon the rate of flow. The highest concentrations of these electrolytes were observed during periods of high flow rates. 6. Horse parotid saliva contained a high concentration of calcium. 7. In the absence of a dietary supplement of sodium bicarbonate, the sodium concentration of the saliva fell after about 21 days. There was an associated increase in the potassium concentration. The addition of a sodium supplement restored the sodium concentration of the saliva within 24 hr.

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Section: Discussionmentioning

confidence: 99%

A study of parotid salivation in the horse

Alexander¹

1966

The Journal of Physiology

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“…For example, Houpt (1959) showed that sheep retained 22-52Vo of the N of a dose of urea given intravenously, and Boda et al (1916) (McDonald 1948). Studies usins t5N have revealed that ammonia oroductioi in the rumen may be equivalent io l7-84A of dietary N intake (Mercer and Annison 1976); these measurements included production of ammonia from endogenous protein and non-protein sources of N. Ammonia serves as a source of nitrogen for bacterial growth (Allison 1969) to the extent that 50-80Vo of microbial N may be derived from ammonia (Mercer and Annison 1976), and after absorption, it is converted to urea in the liver.…”

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The Degradation and Utilization of Endogenous Urea in the Gastrointestinal Tract of Ruminants: A Review

Kennedy¹,

Milligan²

1980

Can. J. Anim. Sci.

241

148

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“…The concentration of free amino acids in the rumen is at all times low (Chalmers & Synge, 1954b), but breakdown products of the amino acids, ammonia (McDonald, 1948(McDonald, , 1952) and volatile fatty acids (el-Shazly, 1952a) are found in high concentration when the diet of the animal contains adequate and suitable protein. Both the prior treatment and the nature of the protein affect the amount of breakdown products found.…”

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confidence: 99%

“…It was the aim of the work described in this paper to obtain more detailed information concerning proteolysis and associated problems in the rumen, using in vitro techniques to avoid difficulties due to the continuous influx of soluble nitrogenous compounds in the saliva (McDougall, 1948), and the continuous passage of soluble nitrogenous compounds across the rumen wall (McDonald, 1948) and of soluble and insoluble cornpounds further down the intestinal tract.…”

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Proteolysis by Rumen Micro-organisms

Warner¹

1956

Journal of General Microbiology

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SUMMARY : Toluene-treated washed suspensions of rumen bacteria break down proteins largely to amino acids ; in the absence of toluene bacterial deaminases are active. Unlike the deaminases, the presence of proteases does not depend, to any great extent, on the presence of readily attacked protein in the diet of the host animal. Extracts of acetone-dried powders of the bacteria also show proteolytic activity. Rumen protozoa are also proteolytic, and ammonia appears to be the end product of their nitrogen metabolism. Ammonia production due to the protozoa is not as sensitive to toluene as is the case with bacteria. Much of the ammonia production in the rumen in the absence of substrate appears to be due to the endogenous metabolism of the protozoa. Extracts of acetone powders, and extracts prepared by simple freezing and thawing of the protozoa, contain active proteases.In an artificial rumen apparatus it was shown that when digestion was complete, about half the N and C of added casein could be recovered as ammonia and volatile fatty acids respectively. Most of the remainder could not be accounted for analytically, and was presumed to be used for microbial growth, which had occurred. When starch or some other polysaccharides were added to the artificial rumen apparatus as well as casein, the production of ammonia was lowered. This was shown not to be due to any effect on proteolysis or deamination, and was presumed to be due to the increased utilization for microbial growth of some breakdown product of casein.From a t least the time of Zuntz (1891), it has been suspected that microorganisms of the rumen split the proteins fed to the host animal; there has been, however, little unequivocal direct evidence for this proteolytic activity. Schlottke (1936) showed in vitro that glycerol extracts of rumen protozoa contained a protease active a t pH c. 6.1, and also a dipeptidase, but was unable to find much activity in glycerol extracts of rumen bacteria. However, Sym (1938) showed active proteolysis a t pH 6.3 by suspensions of rumen bacteria and of protozoa, and also by extracts of acetone powders of these microorganisms; he found peptidase activity weak in his preparations. Both these authors found little or no free protease in the supernatant rumen liquor. Nikitin (

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The absorption of ammonia from the rumen of the sheep

Cited by 197 publications

References 9 publications

A study of parotid salivation in the horse

A study of parotid salivation in the horse

The Degradation and Utilization of Endogenous Urea in the Gastrointestinal Tract of Ruminants: A Review

Proteolysis by Rumen Micro-organisms

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