Prediction of scaled feed intake in weaner pigs using physico-chemical properties of fibrous feeds.

The objective of the present study was to predict scaled feed intake (SFI) using the physico-chemical measurements of feed bulk, such that gut capacity can be estimated in weaner pigs. A basal feed with 13·7 MJ digestible energy and 180 g crude protein per kg DM was diluted to six inclusion levels (0, 80, 160, 240, 320 and 400 g/kg DM) using lucerne hay, maize cob, maize stover, sawdust, sunflower husks or grass hay (veld grass). A total of 124 pigs weighing 18·1 (SD 1·37) kg body weight were used. Water-holding capacity (WHC; g water/g DM), bulk density (g DM/ml), neutral-detergent fibre (NDF) and acid-detergent fibre (ADF) influenced the SFI. The quadratic relationship between SFI and WHC was SFI = 19·1 (SEM 3·49)+10·04 (SEM 1·61) WHC-1·11 (SEM 0·17) WHC² (P<0·01). SFI was also related (P<0·01) to NDF and ADF by quadratic functions SFI = 24·3 (SEM 3·55)+0·12 (SEM 0·229) NDF - 0·00 012 (SEM 0·000036) NDF² and SFI = 30·2 (SEM 1·95)+0·112 (SEM 0·0232) ADF-0·000343 (SEM 0·0000612) ADF², respectively. Using broken-stick analyses, the gut capacity was attained when WHC = 4·53 (SEM 1·25) g water/g DM, NDF = 367 (SEM 29) g/kg DM and ADF = 138 (SEM 77) g/kg DM. In conclusion, although threshold values for each were different, WHC, NDF and ADF contents of bulk feeds provide relationships with SFI that can be used to predict gut capacity in weaner pigs.