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Influence of the Lysine to Protein Ratio in Practical Diets on the Efficiency of Nitrogen Use 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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Twelve gilts were used to investigate the effect of lysine to protein ratio (5.2 g lysine/ 100g CP vs. 6.7 g lysine/100 g CP) in practical diets on nitrogen retention and the efficiency of utilization in growing pigs. Treatments involved 2 levels of dietary lysine (5.2 or 6.7 g/ 100 g CP) and 3 levels of dietary crude protein (11, 14 and 17% in diet). Nitrogen retention was greatest when pigs were fed the control diet containing 17% protein. Nitrogen retention progressively increased as dietary protein increased (p <0.01), but it was not affected by lysine concentration (g/ 100g C)). Apparent biological value (ABV, nitrogen retained/apparently digestible nitrogen) was estimated to be ~50% at the maximum nitrogen retention. ABV was not affected by lysine concentration, but declined (p < 0.05) as the dietary protein level increased. The efficiency of intake N used for maximum nitrogen retention was approximately 44%. One gram of lysine supported approximately 9 to 10 g apparent protein accretion (nitrogen retention횞6.25/lysine intake) in pigs fed control diets. The efficiency of lysine utilization for protein accretion was lower in pigs fed high-lysine diets (6.7 g lysine/ 100 g CP) so that 1 g of lysine accounted for 7 to 8 g of protein accretion in these pigs (p < 0.01). The lysine required to support maximum nitrogen retention in pigs fed high-lysine diets was higher than that in pigs fed control diets, which suggests that lysine was over-fortified relative to crude protein, since practical diets can not be formulated without excess of some amino acids. In summary the concentration of 5.2 g total lysine / 100 g CP in diet is more appropriate for corn-soybean diets than the commonly suggested the content of 6.7 g total lysine/100 g CP. |
| Keywords:
Lysine; Nitrogen Retention; Nitrogen Utilization; Growing Pig |
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