Factors Influencing the Secretion of Nitrogen in Sheep Saliva

Somebs, M.

doi:10.1038/icb.1961.14

Cited by 31 publications

(9 citation statements)

References 7 publications

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“…In sheep given lucerne hay or pellets, the transfer of approximately 1-3 g N/d is probably maintained by salivary secretion of urea (Nolan & Leng, 1972). In sheep given brome grass pellets, salivary secretion attains 5-7 l/d (Kennedy & Milligan, 1978b) which would contribute 0.4-0.6 g urea-N/d, assuming a concentration of plasma urea of 140-150 mg N/1 and that salivary urea concentration was 0.6 that of plasma urea (Somers, 1961). Therefore transport of urea across the rumen epithelium may contribute up to 9 g N/d, or approximately 0.9 of the total transfer.…”

Section: Discussionmentioning

confidence: 99%

“…Weston & Hogan (1967) suggested a maximal transfer of blood urea to the rumen of sheep of approximately 5 g N/d, while Nolan & Leng (1972) concluded that only 1.2 g N/d was transferred in sheep given lucerne (Medicago sativa) hay. Secretion of urea in saliva contributes to the transfer of blood urea to the rumen (Somers, 1961), but Houpt (1959) estimated that transport of urea across the rumen epithelium could account for up to 0-95 of the total transfer. Nolan & Leng (1972) suggested, however, that in their study virtually all the transfer occurred by way of saliva.…”

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confidence: 99%

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Transfer of urea from the blood to the rumen of sheep

Kennedy

Milligan

1978

Br J Nutr

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I. The rate of transfer of plasma urea-nitrogen to rumen ammonia was measured by infusion of 16NH,C1 and [16N]urea into sheep given brome grass (Bromus inermis) or lucerne (Medicago sativa) pellets. Urea was infused into the rumen or abomasum of two sheep given brome grass in order to increase the concentration of rumen ammonia.2. From 6.2 to 9.8 g/d of plasma urea-N were transferred to the rumen of sheep given brome grass pellets and a measurement of 1.3 g nitrogen/d was obtained for a sheep given lucerne pellets. When urea was infused into the rumen of sheep given brome grass pellets the transfer was only 2.8-3.7 g N/d. 3.There was a significant negative correlation between the rate of transfer of plasma urea-N to the rumen and the concentration of rumen ammonia. In the present experiments the transfer of urea from the blood to the rumen was studied in sheep given two diets, using 15N tracer dilution techniques. After it had been found that there were large differences between diets in the transfer of urea-N from the blood to the rumen ammonia pool, urea was infused into the rumen and abomasum of two sheep during two periods in order to establish the effect of increased concentrations of rumen ammonia on urea transfer. Although evidence has been reported (Cocimano EXPERIMENTAL Animals and feeding regimenFive adult Suffolk wethers (aged 1-5-2.5 years), weighing 50-65 kg were used. They were fitted with rumen and abomasal cannulas and individually housed in metabolism cages at 18-25" with continuous illumination. Food was given at hourly intervals by means of an interval feeder for at least 3 weeks before measurements commenced. The diets used were brome grass (Bromus inermis) pellets and lucerne (Medicago sativa) pellets which contained (g/kg dry matter (DM)) 20 N, goo organic matter (OM) and 26 N and 870 OM, respectively.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Transfer of urea from the blood to the rumen of sheep

Kennedy

Milligan

1978

Br J Nutr

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“…The studies of Somers (1961b) indicate that secretion of nitrogen in saliva has an upper limit; this work showed that following a single intracarotid infusion of urea, the secretion of total nitrogen or urea in parotid saliva reached an upper limit when blood urea nitrogen level was approximately 30 mg/100 ml and did not increase with further increase in blood urea concentration. It is possible that a similar limitation to salivary nitrogen secretion existed in the present studies but at a lower blood urea concentration.…”

Section: (E) Transfer To the Rumen Of Nitrogen Infused Per Abomasummentioning

confidence: 98%

“…A large proportion of the salivary nitrogen is urea (Bailey and Balch 1961;Somers 1961a) while Ash and Dobson (1963) have shown that urea is one of the nitrogenous substances entering the rumen through the rumen wall.…”

Section: Introductionmentioning

confidence: 99%

The Transfer of Nitrogen from the Blood

Weston¹,

Hogan²

1967

Aust. Jnl. Of Bio. Sci.

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SummaryUrea providing from 1 to 15 g nitrogen/day was continuously infused per rumen or per abomasum into sheep consuming a diet of chopped wheaten hay.Blood urea was directly proportional to the quantity of urea nitrogen infused. The infusion of urea per abomasum produced an increase in the concentration of ammonia in rumen liquor due to an enhanced transfer of nitrogen from the blood to the rumen.By comparing the increments in rumen ammonia concentration produced by urea infusions per abomasum and per rumen, it was shown that when 2·5 g or less of urea nitrogen were infused per abomasum, transfer of nitrogen to the rumen increased by an amount similar to that infused; increase in the quantity infused beyond approximately 3·5 g nitrogen/day, however, failed to increase nitrogen transfer further. This limit to nitrogen transfer was reached when the concentration of blood urea nitrogen was 16-18 mg/ 1 00 ml. It was calculated, after making certain assumptions, that the maximum amount of nitrogen transferred to the rumen was 4-5 g/day, the equivalent of 1· 5-1· 8 times the body urea nitrogen pool at blood urea nitrogen levels of 16-18 mg/lOO ml.

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“…Transfer of blood urea-N to the rumen Assuming salivary urea-N concentration is 0.60 of that in blood (Bailey & Balch, 1961 ;Somers, 1961) and total salivary flow was 11 litres/d (average reported by Kay (1960)), contributions of salivary urea-N to the rumen were estimated as 0.3 (diet A), 0.6 (diet B) and 1.0 (diet C) g N/d. Although these are only approximations, it would appear that all blood urea-N transferred to the rumen cannot be accounted for by saliva alone, since these values represent only 8, 13 and 38% of the total transfer measured (diets A, B and C respectively).…”

Section: Enrichments Of Microbial-n and Abomasal Nh-nmentioning

confidence: 99%

Kinetics of nitrogen transfer across the rumen wall of sheep given a low-protein roughage

Neutze

Kellaway²,

Faichney³

1986

Br J Nutr

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1, The significance of blood urea-nitrogen transfer to the rumen was examined in sheep given alkali-treated wheat straw supplemented with 3.5 (diet A), 5.9 (diet B) and 11.6 (diet C) g urea-N/kg dry matter (DM).2. Mean voluntary intakes of DM (g/d) were 897, 1149 and 1225 for diets A, B and C respectively, indicating significant (P < 0.05) intake responses to urea supplementation. Digestion studies were conducted at 90% of voluntary intake. Dietary N intakes (g/d) were 7.1, 11.5 and 18.6 for diets A, B and C respectively. 3. Absorption of ammonia-N from the rumen (g/d) was 3.5, 6.7 and 8.9 for diets A, B and C respectively, with all dietary differences being significantly different (P < 0.05). 4.Non-ammonia-N (NAN) leaving the abomasum (g/d) was 9.6, 12.7 and 14.8 for diets A, B and C respectively. Microbial N leaving the abomdsum (g/d) was 6.8, 9.6 and 10.7 for diets A, B and C respectively.Hence, significantly (P < 0.05) more N was provided to the intestines with increased urea supplementation. Net efficiencies of microbial protein synthesis (g N/kg organic matter apparently digested in the rumen), estimated from 16N incorporation, were 24.2, 23.7 and 25.3 for diets A, B and C respectively, and were not significantly different (P > 0.05). . ~~~~ B and C respectively, reflecting the high proportion of total N as urea-N in the diets. Proportions of microbial N derived from blood urea-N were 0.31, 0.21 and 0.12 for diets A, B and C respectively, indicating a decreasing significance of blood urea as a source of microbial N as dietary urea increased ( P < 0.05). 6. Transfer of blood urea-N to the rumen (g/d) was 3.8, 4.7 and 2.6 for diets A, B and C respectively, being significantly (P < 0.05) lower on diet C. Using an estimate ,of the salivary contribution of urea-N to the rumen, it was concluded that there was a significant though not large transfer of blood urea-N across the rumen wall on all diets. 7. Net transfer of blood urea-N to the rumen was estimated from a two-pool model and was +0.4 g/d for diet A, though this was not significantly different from zero. Net transfers for diets B and C were -2.0 and -6.3 g N/d respectively.8. Significant intake responses to exogenous urea supplementation were observed because of a limited capacity to recycle N to the rumen under the conditions of low dietary N supply imposed.

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Factors Influencing the Secretion of Nitrogen in Sheep Saliva

Cited by 31 publications

References 7 publications

Transfer of urea from the blood to the rumen of sheep

Transfer of urea from the blood to the rumen of sheep

The Transfer of Nitrogen from the Blood

Kinetics of nitrogen transfer across the rumen wall of sheep given a low-protein roughage

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