Estimating rumen degradability of forages from semi-natural grasslands, using nylon bag and gas production techniques

Abstract

To obtain insight into ruminal digestion of forages from extensively managed semi-natural grasslands, degradation characteristics and kinetics of silages of three different forages in the rumen of lactating dairy cows were estimated in vitro, using the gas production technique (GPT), and in situ, using the nylon bag technique. Silages originated from intensively managed grassland (IMG), extensively managed species-poor grassland (SPP) and extensively managed species-rich grassland (SPR). Some individual species originating from extensively managed species-poor and species-rich grassland were used to estimate their degradability with GPT, in order to obtain insight into the differences between the main species occurring on these two types of grassland. All samples were also analysed for in vitro organic matter digestibility. In situ degradability was estimated by nylon bag incubation in the rumen of three dairy cows in two different periods. Rate of organic matter degradation was highest for IMG (4.93 and 4.54% h −1), intermediate for SPR (3.50 and 4.11% h −1) and lowest for SPP (2.62 and 2.72% h −1). Also the rates of degradation for protein and neutral detergent fibre were highest for IMG. The undegradable fraction was the same for SPP and SPR. Highest cell wall fermentation was observed for IMG and lowest for SPP, but SPP and SPR did not differ statistically in this respect. Cell wall degradability of the individual species from the species-poor and species-rich grasslands was highest for Lolium perenne and Dactylis glomerata and lowest for Lathyrus pratensis and Anthriscus sylvestris. Based on the in situ and in vivo degradation characteristics it was concluded that SPR appears to have more potential as a component of the ration of dairy cows than SPP.