Assessment of a balance of dietary amino acids required to maximise protein utilisation in the growing pig (20–80 kg liveweight)

Abstract

Reservations about the interpretation of 3 recent empirical estimates of the ideal amino acid balance for the growing pig prompted this study. A basal diet was formulated, in which enzymatically hydrolysed casein supplemented with synthetic amino acids was the sole protein source. The balance of essential amino acids in the diet was close to the mean of the 3 published estimates. Eight entire male pigs of 28 kg initial liveweight were confined in metabolism crates, and fed the basal diet for 20 days. They were then fed a protein-free diet for a further 8 days. The basal diet was fed at a level (based on body weight} calculated to allow a body protein deposition rate of 100 gfday. The protein-free diet was fed at a level which ensured an equivalent intake of all nutrients (except protein) to that of the basal diet. Mean daily excretion of urinary urea nitrogen (N) over 6-day collection periods was 93 and 19 mg/kg^0.75 for pigs fed the basal diet and the protein-free diet respectively. If it is assumed that the difference between these values was attributable to deamination of amino acids from the basal diet, the efficiency of dietary protein utilisation was 0.940. Taking into consideration the difficulties encountered in accurate measurement of irreducible minimum urinary urea nitrogen excretion, it was concluded that the amino acid pattern of the basal diet was close to an ideal balance.

Keywords:

• pigs
• protein metabolism
• ideal protein
• diet
• amino acids
• excretion