Relationship of plasma urea nitrogen and urea-cycle amino acid concentrations in swine to dietary electrolyte balance and water intake

In recent decades, recommendations on dietary protein content have been considerably reduced, while fibre content has been increased. Under these conditions, an adequate dietary amino acid balance could be crucial to optimise feed efficiency. Plasma urea nitrogen (PUN) level could be a good indicator of an amino acid imbalance and its potential has already been studied in other species, but not yet in rabbits. The main objective of the present work was to detect the possible interest of PUN in pinpointing amino acid deficiencies in rabbits. Two experimental diets were formulated from the same basal mixture, following all the recommendations for growing rabbits, except lysine, whose content was variable, following current guidelines in diet P8.1 or lower from those in P4.4 (with 8.1 and 4.4 g/kg dry matter of lysine and with 757 and 411 mg of lysine per MJ of digestible energy). Three different trials were designed: one where the animals were fed ad libitum (AL) and two others in which fasting periods of 10 h were included; one where feeding was restored at 08:00 h (Fast8h) and the other at 18:00 h (Fast18h). A total of 72 three-way crossbred growing rabbits (24 animals for each trial in a split-plot trial) up to a total of 12 recordings were used. Blood samples were taken every 4 h in AL trial and every hour after refeeding up to a total of six controls, in trials Fast8h and Fast18h. The differences between balanced and unbalanced diets in lysine were highest (P<0.001) between 04:00 h and 12:00 h in animals fed ad libitum, and at 3 h after refeeding (21:00 h) in Fast18h. These results suggest that PUN could be an adequate indicator to detect deficiencies in amino acids in growing rabbit diets.

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Amino acid nutrition of the lactating sow: the requirement for dietary lysine

Animal Science ◽

10.1017/s0003356100000763 ◽

1982 ◽

Vol 35 (1) ◽

pp. 15-23 ◽

Cited By ~ 10

Author(s):

R. Wilkinson ◽

D. J. A. Cole ◽

D. Lewis

Keyword(s):

Amino Acid ◽

Linear Regression ◽

Dry Matter ◽

Latin Square ◽

Basal Diet ◽

Milk Composition ◽

Nutritional Adequacy ◽

Urea Nitrogen ◽

Plasma Urea ◽

Lactating Sow

ABSTRACTThe lysine requirement of the lactating sow was examined in two Latin-square experiments using multiparous sows, in mid lactation, each of which suckled a litter of 10 piglets. The lysine requirement was examined by the addition of supplementary synthetic lysine to a basal diet deficient in lysine, to give dietary lysine levels of 6·4 to 17·2g/kg dry matter. The adequacy of the lysine supply was judged by the responses of plasma lysine, plasma and urea-nitrogen, urinary urea-nitrogen and milk composition. Intersecting linear regression lines were fitted to the treatment means. The responses of urinary urea-nitrogen, in the two experiments, indicated that the lactating sow required approximately 48·5 g dietary lysine per day while the response of plasma lysine indicated a requirement of approximately 51 g lysine per day. Plasma urea and milk composition were less useful as indicators of the nutritional adequacy than were urinary urea-nitrogen and plasma lysine.

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Amino and urea nitrogen levels in lambs receiving different nitrogen sources and injections of lysine and methionine

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y69-152 ◽

1969 ◽

Vol 47 (11) ◽

pp. 929-934 ◽

Cited By ~ 2

Author(s):

D. G. Ely ◽

C. O. Little ◽

G. E. Mitchell Jr.

Keyword(s):

Amino Acid ◽

Amino Nitrogen ◽

Nitrogen Sources ◽

Total Amino Acid ◽

Urea Nitrogen ◽

Plasma Urea ◽

Nitrogen Levels ◽

Dietary Nitrogen ◽

Tissue Protein Synthesis ◽

Time Of Feeding

Two trials were conducted to study changes in plasma urea and amino nitrogen of lambs fed different nitrogen sources. In the first trial, zein, zein and urea, or urea were fed as the only dietary nitrogen sources. Nitrogen balance data indicated the superiority of the zein–urea ration. Plasma amino acid concentrations were lower at 4 h after feeding than just before feeding. The concentration of total plasma amino acids was greatest when zein was fed and least when the zein–urea ration was fed. Lysine injections into the systemic blood caused a steady decline in total amino acid concentration up to 60 min after injection when zein was fed. Increases in total concentrations were noted after injection when urea had been fed. Intermediate values resulted in lambs fed the zein–urea ration. Lysine appeared to be the limiting amino acid required for maximum tissue protein synthesis when zein was fed. In the second trial, zein, purified soy protein, urea plus sulfur, and urea without sulfur were fed. Plasma collected from lambs fed zein contained less urea nitrogen at every collection period than those fed the other three nitrogen sources. Urea nitrogen decreased from time of feeding to 4 h after feeding zein and soy but increased after feeding both urea rations. Plasma amino nitrogen decreased from time of feeding to 4 h after feeding all rations. Neither urea nitrogen nor amino nitrogen was affected by intravenous amino acid injections.

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