Impact of nutritional and environmental factors on plasma urea and amino acid concentrations in pigs

Abstract

A repeated measures experiment was conducted to test the hypothesis that concentrations of plasma urea nitrogen (PUN) and 32 free amino acids (PFAA), i.e., 10 essential (EAA), 9 non­ essential (NEAA) and 13 less common amino acids (LCAA), in pigs with two feeding methods are independent of sampling times after feeding. Seven castrated male pigs (mean of 65 kg) with surgically implanted catheters in the jugular vein were randomly assigned to either free access to feed or feeding of two equal-sized meals for 3 c. This study covered three 3-d treat­ ment periods. Blood samples were taken six times in 2-h intervals during the day (0800 to 1800) and again during the night (2000 to 0600). Average concentrations of PUN and most PFAA were not affected by the feeding method and day or night, but there were overall changes in concentrations over six sampling points. The dependence of changing patterns in PUN or PFAA over the sampling points on the feeding method is indicated by the significant interaction of sampling point and feeding method. Sampling points had a linear effect on all EAA, 5 NEAA and 4 LCAA; a quadratic effect on PUN, arginine, phenylalanine, asparagine, glycine, tyrosine, (3-alanine, ornithine and taurine; and a cubic effect on PUN, 8 EAA, 4 NEA.A and 4 LCAA. No interactions of day or night with the feeding method or the sampling points indicate that concentrations of PUN and PFAA between the day and night periods were independent of feeding methods or sampling times. In conclusion, the pigs fed twice daily had postprandial peak average concentrations of 4.92 mmoI/L PUN at 5 h and peak PFAA at 2 h after feeding during a 12-h day or night period. However, the pigs with free access to feed exhibited a 4% rhythmic fluctuation of PUN during the day or night and almost constant levels of most PFAA during a 24-h period. The results also suggest that concentrations of LCAA vary less than concentrations of EAA or NEAA in response to the experimental factors. INDEXING