Studies on the Response Time for Plasma Urea Nitrogen as a Rapid Measure for Dietary Protein Quality in Pigs

Abstract

The optimal response time of plasma urea nitrogen (PUN) was investigated in slaughter pigs fed diets based on barley, wheat or casein as protein sources. Four blood samples were collected during the day from a catheter in the jugular vein: one sample was collected 0.5 h before morning feeding while the other three samples were collected 2, 4 and 6 h after the morning feeding. The effect from previously fed diets on the specific response from the test diet was investigated. However, only the diet fed on the previous day was found to influence the values of PUN before the morning feeding. The reported experiments included nine different diets fed to six pigs in six different feeding designs, all requiring 1 or 2 days for investigating the test diet. The diet used in the morning feeding also significantly influenced the concentration of PUN during the following 6 h. In general, a good agreement was found between the calculated biological value (BV) of the diet and the response of PUN. It was concluded that analysis of PUN can be used as a rapid response parameter for testing the protein quality of the diet and, consequently, this analysis may also be used as a rapid method for determining amino acid requirements in pigs.