The effect of feeding a diet in meal or pelleted form to grow-finisher pigs when delivered as dry, wet/dry or liquid feed on faecal and intestinal microbiome

The aim of this study was to profile the intestinal and faecal microbiome of grow-finisher pigs provided with the same diet in meal or pelleted form when delivered as dry, wet/dry or liquid feed and to investigate whether the differentially abundant bacterial taxa found are correlated with the growth, feed efficiency and/or carcass quality of these pigs. The study involved 216 Danavil Duroc x (Large White x Landrace) pigs penned in same sex (entire males or females) pen groups of 6 pigs of similar weight (average starting weight of ~33.3 kg). Pen groups were blocked by sex and weight before being randomly assigned to 1 of 6 dietary treatments in a completely randomised block design: (1) Dry meal diet; (2) Dry pelleted diet; (3) Liquid meal diet; (4) Liquid pelleted diet; (5) Wet/dry meal diet; and (6) Wet/dry pelleted diet. The diets were fed on an ad-libitum basis for 64 days. The experiment was a 2 x 3 factorial arrangement, with two factors for feed form (meal and pellets) and three factors for feed delivery (dry, liquid and wet/dry feeding). Liquid meal, liquid pellet and wet/dry pellet-fed pigs had the highest average daily gain (ADG) (p < 0.001), while average daily feed intake (ADFI) was highest in liquid meal and liquid pellet-fed pigs (p < 0.001). Feed conversion efficiency (FCE) was lower (improved) in the dry pellet-fed pigs compared to liquid-fed pigs and was similar in pigs fed meal or pellets via dry or wet/dry feeding (p < 0.001). The microbiome of pigs fed meal, rather than pellets, was more diverse in the ileal digesta (p < 0.01), with increased abundances of Megasphaera, Mitsuokella and Prevotella (p < 0.001), while Streptococcus (p = 0.005) and Escherichia-Shigella (p = 0.009) were more abundant in pellet-fed pigs. Prevotella (p < 0.01) and Streptococcus (p < 0.01) were enriched in the caecal digesta and faeces of pigs fed pelleted diets. Lactobacillus was enriched in the caecal digesta and faeces of pigs fed liquid meal (p = 0.05), most likely due to its predominance in the liquid meal diet consumed. Leuconostoc, which was most abundant in the ileal digesta and faeces of liquid-fed pigs, was associated with increased ADFI and poorer FCE across treatment groups (p = 0.05). Additionally, decreased abundance of Turicibacter was associated with increased ADFI in the liquid meal-fed pigs (p = 0.05), which may, in part, explain the poorer FCE of liquid-fed pigs.