Drêches d’alcool de riz dans l’alimentation du porc : réponses de l’animal et du microbiote intestinal | Rice distillers’ by-products in swine diet: animal and intestinal microbiota responses

Rice distillers’ by-product (RDP) is a coproduct from rice fermentation process in the alcohol production and it is a widely used feedstuff in Vietnam and in Asia. But its adequate incorporation into pig diets is still questionable. The objective of this study was to investigate RDP production, their nutritional value and inclusion effects on nutrient digestibility, growth performance, blood profiles, carcass characteristics, meat quality and colonic microbiota of weaned and/or finishing pigs. Therefore, four main experiments were performed according to results outlined below. Production, nutritive value and use of rice distiller’s by-product as feeding for pig raising in Northern Vietnam were investigated in Experiment 1. A total of 120 rice alcohol producers classified by production scales (large, medium and small) were interviewed. Additionally, RDP samples were collected from nine representative producers to analysis their daily chemical composition for one week of storage. Our results indicate that an amount of 3.3 tons dry matter (DM) of RDP was obtained per producer per year. A positive correlation between quantity of RDP production and pig number raised in the household was established (p < 0.05). Amounts of rice distillers’ by-product used in the daily diet of swine in all three household’s scales gradually decreased from pregnant to lactating sows (28 and 18% DM) and varied for fattening pigs (25 to 34% DM). RDP was a rich source in crude protein (26.2% DM), lactic acid (2.3 g/100 g fresh matter), phosphorus (7.5 g/kg DM), iron (104 mg/kg DM) and gross energy (20.4 MJ/kg DM). Its nutritive values were stable under ambient condition during a week (p > 0.05). In experiment 2, nutrient digestibility and energy value of ordinary (ORDP) and glutinous (GRDP) rice distillers’ by-product in growing pigs was evaluated. Glutinous by-product especially showed higher level in crude protein (31% DM) in comparison with RDPO (20% DM). Inclusion of ORDP in diets fed to pigs tended to increase DM intake (p = 0.054) but decreased apparent digestibility of gross energy (p < 0.001) and of crude protein (p < 0.04); while inclusion of GRDP in diets fed to pigs decreased DM intake (p < 0.001) et tended to decrease apparent digestibility of crude protein. Both GRDP and ORDP products negatively affected apparent digestibility of ether extract. Digestible and metabolizable energy of ORDP and GRDP were 17.0 and 16.6, and 17.7 and 17.1 MJ/kg DM, respectively. To study growth performance, nutrient digestibility, blood profile and intestinal microbiota of weaned piglets fed diets containing increasing levels of RDP, Experiment 3 was designed. Weaned piglets fed diets with increasing inclusion levels (0, 15, and 30 % DM) of RDP tended (p ≤ 0.07) to produce higher average daily gain, and lower (p = 0.08) feed conversion ratio; numerically lower apparent total tract digestibility and apparent ileal digestibility of nutrient components were observed; blood parameters were within the normal ranges. However, gene amplicon profiling of 16S rRNA revealed that colonic microbiota composition of weaned piglets changed by inclusion of RDP, and RDP in a favorable way modulated gastrointestinal microbiota composition and improved piglet performance. Finally, in Experiment 4, growth performance, carcass quality characteristics and intestinal microbiota profiles in finishing pigs fed diets with different inclusion levels of RDP were evaluated. Inclusion of RDP (0, 15, and 30 % DM) in finishing pig diets increased average daily gain (p < 0.01) and backfat thickness (p < 0.05). 16S ribosomal RNA gene amplicon profiling showed that RDP was associated with a modulation of colonic microbiota composition and induced an improvement of animal growth and fat deposition. In conclusion, RDP was rich in high quality crude protein and other nutrients and was a suitable feed for pigs. RDP modulated colonic microbiota, which led to trends for improvement in animal growth and fat deposition. Additionally, in a local context RDP used in pig diet improved economical efficiency.