Nutritive value of rhodes grass at different growth stages for ruminant production

Abstract

The nutritive value of Rhodes grass (chloris gayana) at different levels of growth, with minimum fertilisation was studied. Nutritive value is in reference to the chemical composition and digestibility of the grass. The grass was harvested at eight growth stages with respect to time after seedling emergence and height of plants above ground; with the first to last harvests being done at 12cm, 20cm, 30cm, 45cm, 60cm and on average >70cm for the sixth, seventh and eighth harvests. Proximate analysis for the samples showed a steady decline in CP from 8.61% at 4 weeks old to 2.83% at 15 weeks when it was cut as hay at eighth harvest. CF increased from 32.34% at initial harvest to 42.03% during the eighth harvest. This reciprocal relationship between CF and CP agreed with previous reports. DM yield increased from 1.75tonnes per hectare at initial harvest to 14.5t/ha at eighth harvest. Invitro OMD also indicated a steady fall from 75.52% at harvest level one, to 54.1% for the eighth. The drop in CP and OMD, rise in CF were attributed to the increase in lignin content of the grass. Invivo OMD was estimated for the eighth harvest level (62.82%) and compared to the laboratory invitro method. The former was higher than the latter which contrasted with earlier reports. Invivo digestibilities for OM, DM, CF and GE were consistent with other figures reported. The analysis helped to determine how much a ruminant animal would obtain in terms of nutrients at each harvest level. It was concluded that the optimum cutting stage would be at 45-60 CJ*