Effects of different sources and levels of dietary fibre in diets on performance, digesta characteristics and antibiotic treatment of pigs after weaning

Abstract

An experiment was conducted in male weaner pigs to examine the effects of different sources and levels of dietary fibre (DF) on performance and aspects of fermentation and digestion after weaning. Pigs were allocated in a completely randomised design having five experimental treatments, with six pigs allocated to each treatment. The diets used were: (i) cooked white rice (R) plus an animal protein supplement (R-AP); (ii) R+HiMaize (high-amylose maize starch) (R-HACS); (iii) R+lupin isolate (R-LI); (iv) R+HiMaize+lupin isolate (R-HACS+LI); and (v) a commercially-based weaner diet (COM). These ingredients were chosen because they represented a mix of soluble and insoluble sources of DF. The measured total DF content ranged from 27 g/kg in diet R-AP to 300 g/kg in diet R-LI. Pigs were fed on an ad libitum basis for 14 days, then euthanased for sample collection. Pigs fed diet R-AP consumed more dry matter (DM) ( P=0.037) than pigs fed diets R-HACS+LI and COM, and tended ( P<0.15) to show greater rates of live- and empty-bodyweight gain than pigs fed diets containing higher levels of DF. Fermentation indices such as pH and volatile fatty acid (VFA) concentrations were generally reduced ( P<0.05) in pigs fed diets R-AP and COM, particularly in the distal colon. The pool of VFA in the colon was greatest in pigs fed diets R-HACS, R-LI and COM (45, 45 and 36 mmol per pig, respectively, P<0.001), and the colonic VFA pool explained proportionally 0.79 ( P=0.028) of the variation in the empty weight of the colon. The total intake of insoluble DF explained proportionally 0.75 and 0.80 of the variation in the quantity of colonic contents ( P=0.057) and the empty colonic weight ( P=0.041), respectively. In a retrospective analysis of the number of pigs treated with antibiotics for post-weaning diarrhoea, pigs offered diet R-AP did not require any treatment whereas pigs on all other diets required more injections (0 versus a median score of 3.0–4.5 injections, P=0.004). Under the conditions of this experiment, pigs offered a diet based on cooked white rice, animal protein sources and 50 g/kg soyabean meal ate more feed after weaning and required no therapeutic antibiotic treatments compared to pigs offered higher levels of dietary DF. The possible implications of such findings are discussed.