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Observations on the effect of protein intake and stage of gestation on the proportion of urinary nitrogen excreted as urea in sheep

Published online by Cambridge University Press:  27 March 2009

J. J. Robinson ,
D. Scott  and
C. Fraser
J. J. Robinson
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen, AB2 9SB
D. Scott
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen, AB2 9SB
C. Fraser
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen, AB2 9SB
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Summary

The effect of altering the level of protein intake on urea excretion in ewes was assessed in two separate experiments.

In Expt 1, 14 pregnant (during the last 20 days of gestation) and 10 non-pregnant ewes were each offered a different level of digested N intake in the range 5–25 g/day. At all levels of protein intake urea N excretion was lower in pregnant than in nonpregnant ewes.

In Expt 2, 21 pregnant ewe lambs were each offered one of three diets supplying mean intakes of 83 (T1), 113 (T2) or 147 (T3) g crude protein/day. During the last 100 days of gestation the mean levels of urea N excretion were 6·9, 11·0 and 15·2 g/day for T1, T 2 and T 3, respectively. The corresponding values for urinary N excretion were 9·3, 13·8 and 18·2 g/day. At all levels of protein intake urea N excretion was lower just prior to parturition than 95 days prepartum; the difference was correlated with lamb birth weight and maternal body-weight change.

A notable feature of both experiments was the low level of urea N excretion by the pregnant ewes in late gestation, at low protein intakes. It would appear that when energy intake is adequate the decrease in urea N excretion associated with pregnancy is a direct result of an increased N requirement for maternal and/or foetal growth.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 80 , Issue 3 , June 1973 , pp. 363 - 368
Copyright
Copyright © Cambridge University Press 1973

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