In vitro digestion and fermentation characteristics of tropical ingredients, co-products and by-products with potential use in diets for rabbits

The objective of this work was to evaluate and classify 16 tropical ingredients, co-products and by-products with potential use in rabbit feeding. We evaluated alfalfa hay, maize, wheat bran, soybean meal, crumbled maize with straw and cob (CMSC), soybean hull, citrus pulp, sugarcane bagasse, coffee husk, macauba seed cake meal (Acrocomia aculeata; MSCM), desmanthus hay (Desmanthus virgatus), sicklepod hay (Senna obtusifolia), neem hay (Azadirachta indica), Sodom apple hay (Calotropis procera), Barbados gooseberry hay (Pereskia aculeata) and moringa hay (Moringa oleifera). Chemically, were quantified dry matter (DM), crude protein (CP), ether extract (EE), neutral detergent fiber (aNDF), acid detergent fiber (ADF) and their nitrogen content (NDIN and ADIN, respectively), lignins, hemicelluloses, cellulose and non-fiber carbohydrates (NFC). Were evaluated the in vitro digestibility (ivDMdig) and degradability (ivDMdeg) of DM, and fermentation parameters, maximum amount of gas produced (B, mL/g DM), specific rate of gas production (C), decay of the specific rate of gas production (A), maximum fermentation rate (MFR, mL/h), time for maximum fermentation rate (TMFR, h) and latency time (LAG, h), using caecal inoculum for the in vitro evaluations. Were performed the hierarchical clustering on principal components (HCPC) of the data collected in the in vitro evaluations and obtained the matrix containing Pearson's correlation coefficients between the chemical composition and the in vitro parameters. The values of DM, CP, Ash, EE, aNDF, ADF, lignins, hemicelluloses, cellulose, NDIN, ADIN, GE and NFC ranged from 857 to 906 g/kg, 22.9-552 g/kg DM, 7.0-153 g/kg, 5.26-136 g/kg DM, 204-697 g/kg DM, 20.6-493 g/kg DM, 2.27-226 g/kg DM, 73-443 g/kg DM, 18.3-437 g/kg DM, 25.3-395 g/kg CP, 19.9-227 g/kg CP, 13.3-21.7 MJ/kg and 38.9-690 g/kg, respectively. The results for ivDMdig, ivDMdeg, B, C, A, TMFR, MFR and LAG ranged from 0.21 to 0.84, 0.22 a 0.67, 79.9-348 mL/g DM, 2.75-4.44, 0.08 to 0.30, 8.58-38.8 h, 2.99-9.32 mL/h and 0.07-6.51 h, respectively. The results of the HCPC analysis determined the classification of the feeds into four groups: Group I contain sugarcane bagasse, coffee husk and citrus pulp; Group II contain soybean hull, desmanthus hay, MSCM, moringa hay and Barbados gooseberry hay; Group III contain alfalfa hay, Sodom apple hay, soybean meal, wheat bran, sicklepod hay and neem hay and Group IV contain maize and CMCS.