Title: Assessment of cutting time on nutrient values, in vitro fermentation and methane production among three ryegrass cultivars
Authors: Chunmei Wang, Fujiang Hou*, Metha Wanapat, Tianhai Yan, Eun Joong Kim, Nigel David Scollan
Journal: Asian-Australasian Journal of Animal Sciences (农林科学4区，IF2018=1.227)
Abstract: Objective: The 3 × 3 factorial arrangement was used to investigate if either high water-soluble carbohydrates (WSC) cultivars or grass cut in Noon and PM could improve nutrient values and in vitro fermentation characteristics.
Methods: The 3 cultivars mowing at 3 diurnal time points contained a benchmark WSC ryegrass cultivar ‘Premium’, and 2 high WSC cultivars AberAvon and AberMagic, which contained, on average, 157, 173 and 193 g/kg DM of WSC, and 36.0, 36.5 and 34.1 g/kg DM of N during 7th regrowth stage, respectively. The fermentation jars were run at 39 °C with gas production recorded and sampled at 2, 5, 8, 11, 14, 17, 22, 28, 36 and 48 h. The rumen liquid was collected from 3 rumen fistulated cows grazing on ryegrass pasture.
Results: High WSC cultivars had significantly greater WSC content, in vitro DM digestibility (IVDMD) and total gas production (TGP), and lag time than Premium cultivar. Methane production for AberMagic cultivar containing lower N concentration was marginally lower than that for AberAvon and Premium cultivars. Grass cut in Noon or PM contained greater WSC concentration, IVDMD and TGP, and lower N and NDF contents, but CH4 production were also increased, compared grass cut in AM. Meanwhile, the effects of diurnal cutting time were qualified by cultivars, such as in vitro CH4 production for AberMagic was not affected by cutting time. The IVDMD and gas production per unit of DM incubated were positively related to WSC concentration, WSC/N and WSC/NDF, respectively, and negatively related to N and NDF concentrations.
Conclusion: These results imply either grass cut in Noon or PM or high WSC cultivars could improve nutrient values, IVDMD and in vitro total gas production, and AberMagic cultivar also have slightly lower CH4 production compared to AberAvon and Premium. Further study is necessary that if the increase of CH4 production response to shifting AM cutting to Noon and/or PM cutting could be compensated by high daily gain contributed by increased WSC concentration and DM digestibility.