Sugarcane bagasse: a novel insoluble fibre source for poultry

In Australia, 35 million tonnes of sugarcane are harvested annually which produces approx. 10 million tonnes of a by-product called bagasse. Sugarcane bagasse is an insoluble fibre source and recent studies in broilers indicated that bagasse can be added at 2% in both normal and reduced protein (RP) diets to improve FCR by 2-3 points and weight gain by 30-40 g (Sharma et al., 2021a,b). Thus, sugarcane bagasse may be a novel insoluble fibre source for poultry. Follow-up studies were conducted to investigate the chemical composition of various insoluble fibre sources as well as the mode of action of bagasse as it stood out.

The methods are reported in detail in previous study (Sharma et al., 2021a). In short, Ross 308 broilers (n = 672) were assigned to 6 treatments with 8 replicates of 14 birds each. The treatments were: a normal protein diet, a RP diet (-20 g/kg protein) and RP diets added with sugarcane bagasse at 20 g/kg, lignocellulose at 10 g/kg, oat hulls at 30 g/kg, or soy hulls at 30 g/kg. The basal diet was the same for all fibre sources and the formulations were adjusted by adding Celite, an inert indigestible component. On d 24, three birds/pen were sampled and digesta samples were collected from the distal jejunum, ileum and caeca to measure apparent digestibility coefficients of starch, protein and amino acids; and selected microbiota composition using qPCR. Tissue samples were collected from the jejunum and pancreas to measure the expression of genes related to digestive enzymes, tight junction proteins and nutrient transporters. Data were subjected to one way ANOVA using JMP v.14 (SAS Institute Inc, Cary, NC). Significance was determined at P < 0.05 using Tukey's HSD test.

Lignocellulose contained the highest concentration of crude fibre (657 g/kg) followed by bagasse (452 g/kg), soy hulls (377 g/kg) and oat hulls (310 g/kg). Bagasse contained the highest concentration of insoluble NSP (536 g/kg) followed by lignocellulose (489 g/kg), oat hulls (474 g/kg) and soy hulls (451 g/kg). Lignocellulose contained the highest concentration of lignin (268 g/kg) followed by bagasse (181 g/kg), oat hulls (152 g/kg) and soy hulls (38 g/kg). Soy hulls contained the highest concentration of crude protein (CP, 93 g/kg) followed by oat hulls (31 g/kg), bagasse (10 g/kg) and lignocellulose (3 g/kg). The birds offered a RP diet with insoluble fibres had no effects (P > 0.05) on water to feed intake ratio compared to those offered a RP control diet. The birds offered a RP diet with bagasse or oat hulls had a higher (P < 0.05) relative gizzard weight compared to those offered a RP control diet. The reduction in dietary CP increased (P < 0.01) the ileal starch digestibility coefficient. The birds offered a RP diet with either bagasse or soy hulls had a lower (P < 0.01) ileal starch digestibility coefficient compared to those offered the RP control diet. Bagasse addition in the RP diet also lowered (P < 0.05) the CP digestibility coefficient in the jejunum but not (P > 0.05) in the ileum. The birds offered the RP diet with either oat hulls or bagasse had the lowest counts of total bacteria in the ileal contents compared to others and lower Lactobacillus counts in the caecal contents compared to those offered the RP diet alone or with soy hulls. The reduction in dietary CP decreased (P < 0.05) the expression of a digestive enzyme AMY2A gene in pancreas. The addition of either of the four insoluble fibres to the RP diet had no effect (P > 0.05) on the expression of AMY2A compared to the RP treatment but bagasse, lignocellulose and soy hulls added RP diets had similar AMY2A expression as the normal protein treatment.

ACKNOWLEDGEMENTS: This research was funded by the AgriFutures Australia.