Volume 37, 101-110

Tropical Grasslands (2003) Volume 37, 101–110

Forage yield, nutritive value, feed intake and digestibility of three grass species as affected by harvest frequency

NGO VAN MAN¹ and HANS WIKTORSSON²

¹ Department of Animal Nutrition, University of Agriculture and Forestry, Thu Duc, Ho Chi Minh City, Vietnam
² Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Uppsala, Sweden

Abstract

Two experiments on the effects of cutting interval on forage production, nutritive value, feed intake and digestibility of elephant grass (Eg) and two guinea grass (Gg) cultivars 280 and I.429, were carried out. Three grasses harvested at 4 cutting intervals (4, 6, 8 and 10 weeks) were compared in a split plot design in the production experiment. In the feed intake and digestibility experiment, 3 grasses and 3 cutting intervals (4, 6 and 8 weeks) were examined in a 3 x 2 change-over design with 6 crossbred Holstein heifers.
Forage DM production increased as length of cutting interval increased and forage quality, in terms of CP and cell wall concentrations, decreased. The yields of DM, CP, digestible DM and digestible CP were highest in Gg 280 followed by Gg I.429 and Eg.
Mean intakes of forage (DM basis) of Eg, Gg 280 and Gg I.429 were 90.4, 104.6 and 94.5 g/kg Lwt^0.73, respectively, with no effect of cutting interval. With the decline in crude protein concentration in older forage, the CP intake of around 13.4 g/kg Lwt^0.73 from the 4-week cuts declined to about 6.7 g/kg Lwt^0.73 in the 8-week cuts. Digestibility of dry matter and crude protein decreased significantly as cutting interval increased, with no differences between grass species.
To obtain the best balance between dry matter yield and forage quality, the optimum cutting frequency seems to be about 6 weeks. There is a possibility that this could be extended to 8 weeks for elephant grass.