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Patterns of Nitrogen Excretion in Growing Pigs |
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K. U. Lee, R. D. Boyd, R. E. Austic, D. A. Ross, In K. Han |
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| Abstract |
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Three crossbred gilts weighing 61 2 kg (mean SD) and three gilts weighing 52 3 kg on the day before the first treatment began (d-1) were used for each of two experiments (Exp. 1 and Exp. 2), respectively. In Exp. 1, all pigs were fed the experimental diet (CP 19%) from d-7 to the end of study (d 21) to verify that nitrogen retention is constant during the 21 -d period. In Exp. 2, pigs were fed the control diet (CP 15.5%) from d -7 to d 8 and then the low-lysine diet from d 9 to d 16 in order to determine how rapidly dietary changes in amino acid composition results in a new equilibrium for nitrogen metabolism. The amount of urine nitrogen loss was not different over 21 days (p > 0.10). Rates of nitrogen retention were not different among pigs (p > 0.10) nor over time (p > 0.10). Average nitrogen retention during the period was 1.00g / kg BW0.75 per day. The apparent biological value was 41%, which did not change over the 3-week period (p > 0.10). The overall efficiency of nitrogen use for nitrogen retention was 35% (Exp. 1). The amount of nitrogen loss in urine and the efficiency of nitrogen utilization for nitrogen gain reached a new equilibrium within 2 to 3 d after the diet was changed. The low-lysine diet resulted in a 20% increase of nitrogen loss in urine (p < 0.001) and a 9% decline in efficiency of nitrogen use for nitrogen retention (p <0.001). Nitrogen retention while the pigs were fed the control diet was also higher than the retention when pigs were fed the low lysine diet (p < 0.001). The efficiency of nitrogen use for nitrogen retention in pigs fed the control diet was 57% (Exp. 2), which was higher (p < 0.001) than that from pigs fed the low-lysine diets (52%). |
| Keywords:
Pigs; N Retention; N Metabolism; Lysine |
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