Ruminal degradation kinetics of dry and wet forages carbohydrates: gas production technique

Abstract

Chemical analysis of carbohydrates fractions and determination their carbohydrates digestion rates in some foods obtained under tropical conditions and semiarid regions, were accomplished. Dry forages were studied (hays of ‘mata-pasto’, ‘sabiá’, ‘juazeiro’, ‘mororó’, star grass, leucaena leaf, oat, and Tifton 85 grass), as well as, wet forages (corn, sorghum and palm silages, and also fresh forage cactus). The kinetics parameters of non-fibrous carbohydrates (NFC) and B2 fraction were estimated using cumulative gas production technique. Among the studied foods, there was considerable variation in chemical composition and in the soluble carbohydrates degradation rates. Comparing the kinetics parameters of native forages to Northeast it was verified that the high content of C fraction in of ‘juazeiro’and ‘mororó’ hay influenced in carbohydrates ruminal degradation kinetics, where the final gas volume for these hays were 6.88 and 2.58mL, respectively. The fermentation of ‘mata-pasto’ hay resulted in a higher gas production (16.38 mL) for total carbohydrates (TC) as well as the higher degradation rate (0.0276%/h) and shorter time for colonization (4.29h). For oat hay, it was observed that the values for A+B1 fraction were higher (389.6 g/kg) in relation to the Tifton 85 grass hay (300.3 g/kg) and star grass hay (344.5 g/kg), and lower for the B2fraction (441.6%). It was observed that sorghum silage had a higher gas volume (24.70 mL) compared with corn silage (16.44 mL). The cumulative gas production technique allows the estimative of degradation rates and provides further information about the ruminal fermentation kinetics of foods.