Table 1.

Inclusion and exclusion criteria used to select studies for the statistical analysis of feed intake regulation

Component	Inclusion	Exclusion
Study design	Quantitative, in vivo: dose–response study	Descriptive; qualitative; in silico; in vitro
Population	Growing (i.e. pigs that overcame stress associated with weaning) and finishing (50–100 kg initial live weight) pigs irrespective of breed	New-born piglets; weaning pigs; sows
Subpopulation	Barrows (castrated males); boars (entire males); gilts	–
Treatment	A minimum of four homogenous feeds differing in their P concentration (as the estimated P requirements for maintenance and growth are imprecise, especially across different pig breeds, several P levels are needed to find the point of response, if any) Once assigned to a given feed, pigs were fed ad libitum throughout the trial duration	Other nutrients (energy, protein, minerals other than P) varied and supplied below the estimated requirement Exogenous phytase supplementation Pigs given choice to select their own diet Pigs fed an allowance
Primary outcome	ADFI for each feed treatment group	–
Additional reported data	Average initial and final body weights for each treatment group Sufficient feed composition information to estimate STTD P	–

ADFI, average daily feed intake; STTD P, standardised total tract digestible P.