Id # 09-40 Intake and Qualitative Aspects of Guinea Grass Grazed by Sheep over Three Different Seasons

The objective of this study was to determine the influence of season on intake by sheep as well as certain selected qualitative characteristics of Panicum maximum (cv Gatton) (Guinea grass) at the mature growing stage. The lower DM content of the spring and summer grass (41.6 and 40.2%) did not hamper DOMI (48.1 and 26.7 W/d), respectively. The N concentration of the spring and summer grass was well within the limit required for optimal rumen microbial production (1.8 2.0%). The high cell wall components of the winter grass resulted most probably in a significant lower IVDOM value (55.5%). The IVDOM values of the spring and summer grass (65.3 and 62.3%) were on the high side for a sub-tropical grass. The lower N content of the summer and winter grass resulted in subsequent lower rumen NH3-N levels (8.9 and 5.3 mmol/100 mL). The winter rumen NH3-N level could have been marginal in terms of rumen microbial activity. The lower VFA values of the summer and winter grass (13.7 and 12.0 mmol/100 mL), could have resulted from a low carbohydrate content in comparison with the N content of these grasses. The significant lower acetic:propionic acid ratio (4.1) of the spring grass suggested a higher quality than both the summer and winter grass ratios (4.6 and 4.7). The significant higher DOMI of the spring pasture (48.1 g/W/d) suggested a potential growth rate of 200 g + of 30 kg lambs. Both the DOMI values of the summer and winter grass (26.7 and 23.3 g/W/d) should fulfill at least the maintenance requirements of grazing sheep.