Effect of levels of irrigation on forage standing crop and quality of WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing



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Incorporation of Old World bluestem grasses into the forage/beef production system on the Texas High Plains promises acceptable results, but information on grass responses to different moisture conditions and grazing is lacking. This study investigated the effect of three levels of irrigation on forage standing crop, forage quality, and steer performance on WW-B.Dahl [Bothriochloa bladhii (Retz) S.T. Blake]. Forage utilization and economic analysis on the beef production capabilities of this grass were also evaluated. The study was conducted in Lubbock County, Texas during consecutive summers, 2003 and 2004, in a 54 hectare of WW-B.Dahl pasture. Three irrigation levels were established: no irrigation (NI), low irrigation (LI) applying 25.4 mm of water every 20 days, and high irrigation (HI) applying 25.4 mm of water every 10 days. Three grazing periods of 28 days also were arranged. Steers with initial average weight of 198 kg were used for the grazing trial. Steers were fed with a whole cottonseed supplement (S), (0.454 kg/head/day fed three times a week) and no supplement (NS). Forage standing crop in both years was affected by irrigation. Higher forage standing was observed for LI during the first year with 1,650 kg ha-1. For the second year HI produced the higher amount of forage with 2,211 kg ha-1. Irrigation affected crude protein (CP) content during 2004 and the highest CP value (7.3%) was detected in LI. In vitro dry matter digestibility, neutral digestible fiber, average daily gain, and average gain per hectare were not affected by irrigation in either year. Supplementation had an effect in ADG in 2004. Forage utilization was no affected in 2003 and 2004 neither by irrigation nor by supplementation. The economic analysis showed that beef production was more profitable in dryland-no supplement scenario in 2003 and dryland-supplement scenario in 2004. Profit in dollar/ha in 2003 and 2004 under these scenarios was $306 and $223 respectively. Overall results for this study suggest that WW-B.Dahl has potential to improve beef production under dryland conditions in the Texas High Plains.