The effect of dietary P level on the digestibility and output of P and nitrogen.

摘要

Five barrows (Duroc x Landrace x Yorkshire) with an average initial body weight of 27.9 kg were used in a 5x5 Latin-square-design to evaluate the effect of different dietary P levels on the digestibility and output of P and nitrogen. The experimental diets contained 5 true digestible P levels (from 0.16% to 0.39%), and the ratio of total calcium to true digestible P (TDP) was 2:1. The results indicated that the true digestibility of P increased (P<0.05) linearly with increasing dietary TDP level below 0.26%. The true P digestibility of dietary TDP level 0.39% (Diet 5) was lower (P<0.05) than dietary TDP level 0.26% (Diet 4). The true P digestibility was highest (56.6%) when dietary TDP was 0.34%. Expressed as g/kg DMI, fecal P output increased (P<0.05) linearly with increasing P input. On the basis of g/kg fecal DM, fecal P output was highest (P<0.05) for Diet 5, and fecal P output was lowest for Diet 4. The apparent digestibility of CP did not differ (P>0.05) among the five diets, the average nitrogen output of 12.14 g/d and nitrogen retention of 66% to 74% (P>0.05). These results suggest that there is no interaction between dietary P and CP protein levels. Therefore, dietary P levels may not affect the digestion and absorption of dietary nitrogen in growing pigs.