Technical review of the energy and protein requirements of growing pigs: protein

A review of work reported in the literature was used to present quantitativ e descriptions of protein use in the growing pig. These are detailed in the text, which also points to preferred values, and to anomalies and lacunae. The review was prepared with the objective of allowing from its content th e inclusive and quantitative modelling of amino acid requirement. Requireme nt was approached as the sum of the component factors: maintenance and prot ein retention. Ileal trite digestible protein and amino acid requirements a re presented in a form consistent with that forwarded for energy. Thus both energy and protein elements can be conceptualized within a single coherent framework. Priority uses for absorbed amino acids were assumed to be (a) t o support endogenous protein losses resultant from the passage of food and incomplete re-absorption prior to the terminal ileum, (b) to replace lost h air and skin, and (c) to cover the basic maintenance losses which will occu r as a result of minimal protein turn-over even when protein retention is z ero. The bulk of the protein requirement was directly linked to the daily r ate of protein retention, for which the linear-plateau response was accepte d. For determination of the maximum rate of protein retention the Gompertz function was proposed, although the use of a single value throughout the gr owth period was not dismissed. The balance of amino acids for protein reten tion is specified as different from that for maintenance. Central to the ap proach was the proposal that the inefficiency of use of Heal digested ideal protein, even when not supplied in excess, was an expression of protein lo sses occurring as a result of protein turn-over. The requirement for the sa tisfaction of the losses from protein turn-over occurring as a consequence of protein retention, and therefore additional to the requirements for main tenance, was identified. Quantfication was attempted with sufficient succes s to warrant its inclusion into requirement estimation. It was concluded th at this element addressed previously inadequately explained protein utiliza tion inefficiencies. Algorithms are presented based upon protein turn-over which appear to be consistent with enipirical findings.