Effects of dietary protein and potassium contents on plasma urea nitrogen and amino acids in relation to performance of swine

Abstract

Ninty-six 51 kg-pigs were used to determine effects of dietary protein and potassium levels on concentrations of plasma urea nitrogen (PUN) and free amino acids. Pigs were fed four diets containing 13 or 15% of protein and 0 or 0.4% of potassium addition. Gilts took more days to reach an average weight of 110 kg with lower PUN and less backfat than barrows (P < 0.05), but sex did not affect concentrations of plasma free amino acids (P > 0.10). The pigs fed 15% protein diets had higher PUN (P < 0.01) and plasma threonine and isoleucine (P < 0.05), but lower (P < 0.05) plasma lysine, glutamic acid and glycine than pigs fed 13% protein diets. The 0.4% potassium addition resulted in a tendency to increase PUN (P = 0.06) and a decrease in concentrations of plasma alanine, glutamic acid and glycine (P < 0.05). There was an interaction between protein and potassium treatments (P < 0.05) in which plasma lysine concentration decreased with potassium addition to the 13% protein diet but increased with potassium addition to the 15% protein diet. The results indicate that lower PUN concentrations in gilts were associated with improved efficiency of deposition of dietary nitrogen, resulting in improved carcass grade compared with barrows receiving the same dietary treatments. Key words: Plasma urea nitrogen, free amino acids, protein, potassium, pigs