In vitro Evaluation of Different Levels of Cashew (Anacardium occidentale) Nut Meal Supplementation on Rumen Fermentation Kinetics and Digestibility

Abstract

Background: Globally, safeguarding food and nutritional security of ever increasing population demands sustainable crop and livestock production. While urbanization, decrease in cultivable land and stiff feed-fuel-food competition accompanied with skyrocketing price of conventional feedstuffs hinders the sustainable livestock production. Hence, it necessitates search and exploration of alternative feed resources along with judicious utilization of existing feed resources. In this context, Cashew nut meal (CNM) is one such alternative feed resource but the studies pertaining to its optimum level of inclusion in animal diet is scanty. Therefore, the study was conducted to assess the effect of incorporating varying levels of cashew nut meal (CNM) as a supplement on in vitro rumen fermentation kinetics and digestibility. Methods: Seven distinct compounded feed mixtures (CFM) were formulated, with CNM progressively replacing 0 (C0), 10 (C1), 20 (C2), 30 (C3), 40 (C4), 50 (C5), and 60 (C6) per cent of the soybean meal (SBM) protein present in the control CFM. Additionally, seven experimental complete diets (T0 to T6) were prepared by blending these CFM with Super Napier (Pennisetum purpureum x Pennisetum glaucum) hay in a 40:60 ratio. These diets were subjected to rumen in vitro gas production (RIVGP) study with cumulative gas production measured at 0, 2, 4, 6, 8, 12, 16, 24, 36, 48, 60, 72 and 96 h post-incubation. Subsequently, in vitro dry matter digestibility (IVTDMD) and neutral detergent fiber digestibility (NDFD) of the diets were determined using a modified in vitro two-stage technique. Later, total volatile fatty acids (TVFA) were estimated using gas chromatography. Result: Analysis of chemical composition revealed that CNM contains good protein of 256.5 g/kg. The potential gas production (D) and the rate and extent of gas production (c) for diets containing CNM ranged from 54.63 to 60.24 mL and 0.036 to 0.043 h-1, respectively. IVTDMD and NDFD analysis of the seven diets fell within the range of 79.12% to 80.80% and 64.72% to 66.47%, respectively. The estimated TVFA for seven diets ranged from 17.87 to 23.65 mM. Further, the metabolisable energy (ME) of diets ranged from 7.89 to 8.08 MJ/kg DM. Importantly, no significant differences were observed in rumen fermentation kinetics parameters, IVTDMD, NDFD and TVFA among treatments (T0 to T6). In conclusion, cashew nut meal could be used as an alternative to soybean meal in compounded feed mixtures of ruminants up to 30% (w/w) without any adverse effect on rumen fermentation pattern and digestibility.