Performance of light vs. heavy steers grazing Plains Old World bluestem at three stocking rates.
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Authors: C. J. Ackerman, H. T. Purvis II, G. W. Horn, S. I. Paisley, R. R. Reuter, and T. N. Bodine
Date: 2001
Journal: Journal of Animal Science
Volume: 79
Number: 2
Pages: 493-499
Summary of Methods: The effects of increasing stocking rates on live weight gain and gain/hectare using light-weight (141 kg) and heavy-weight (265 kg) steers grazing Plains Old World bluestem (Bothriochloa ischaemum) was examined at the Bluestem Research Range near Stillwater, Oklahoma (36˚ 04’ N; 97˚ 13’ W). Stocking rates were calculated live weight/ha and not by number of steers. Three stocking rates (light, moderate and heavy) were examined over a 69 day grazing season beginning in May. Animal performance in terms of average daily gain (ADG) and time spent grazing by both steer weight groups was collected for this study. Diets were sampled through fecal and ruminal fistula collections. Samples were analyzed for chromium concentrations, OM digestibility, Kjeldahl nitrogen and masticate organic matter disappearance (OMD).
Article Summary / Main Points: Average daily gains (ADG) were greater for heavy-weight steers than light-weight steers in both years, but gain/hectare was greater for light-weight than heavy-weight steers in both years. Adjusting stocking rates as kilograms of body weight per hectare rather than number of animals will allow for greater gains/hectare in light-weight steers. Forage intake was greater in light-weight steers than heavy-weight steers when expressed as g/kg of body weight. As stocking rates increased during the first year, average daily gains of heavy-weight steers decreased while stocking rates did not affect the ADG of light-weight steers. During the second year the study results were the opposite, possibly due to variation in year-to-year forage mass and quality. Steers in the light stocking rate spent less time grazing than steers in the moderate to heavy stocking rates and there was no difference in the amount of time spent grazing in moderate and heavy stocking rates. Gain/hectare increased at a greater rate as stocking rates increased for light-weight steers than for heavy-weight steers, implying greater potential for gain/hectare and subsequent profitability of utilizing light-weight calves at every stocking rate.
Vegetation Types: Tallgrass Prairie
MLRA Ecoregions: 80A Central Rolling Red Prairies
Agrovoc Control Words: Animal performance Grazing Stocking rates
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: animal performance, animal weight, average daily gains, cattle, grazing, plains old world bluestem, stocking rates
Annotation: Application of these results needs to be done with caution knowing this study was highly controlled and manipulated. Forage quality and availability was enhanced and regulated within pastures with fertilizer applications and annual residual forage removal, while individual animal performance was constrained with small pasture isolation. Additionally, animal behavior patterns and mechanisms along with foraging preferences and cue-consequence specificity were neglected in this study, possibly creating the various conflicting results found.
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