Submitted to: Applied Animal Behaviour Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2002
Publication Date: 8/1/2002
Citation: Fehmi, J.S., Karn, J.F., Ries, R.E., Hendrickson, J.R., Hanson, J.D. 2002. Cattle grazing behavior with season-long free-choice access to four forage types. Applied Animal Behavior Science. v. 78. p. 29-42. Interpretive Summary: Proper grazing management is essential in all grazing systems, but it is critical in continuous systems. In order to develop functional season-long grazing systems, there is a need for appropriate grazing behavior data to facilitate development of systems that work with the animal's natural grazing tendencies, rather than against them. Thus, an experiment was conducted to investigate the affect of season-long, free-choice grazing on weekly cattle grazing behavior and resource use. Grazing behavior of yearling steers was assessed by 3 methods, on two replicate 24.4-ha grazing enclosures containing smooth bromegrass, crested wheatgrass, western wheatgrass and native range. There were three sub-areas within each forage type; one area contained a water source, a second area contained salt, and the third area contained forage that had been deferred from grazing for three years before the experiment began (rested). Resource use was tracked dby analysis of before and after (the 3-year study) pasture aerial photos, weekly observation of animal activity in all portions of the enclosures, and analysis of forage utilization data. As each season progressed, use of smooth bromegrass declined and use of crested wheatgrass and western wheatgrass increased. Use of native range remained relatively constant and low throughout the study. Previously rested pasture sub-areas had substantially more grazing than areas with salt or water. Statistical evaluation of grazing behavior data, showed a gradual week to week shift in forage preference. Data indicate that cattle can rotate themselves among various pasture types in a free-choice system, and suggest that season-long free-choice grazing may be an effective system, if a variety of forage types are available.
Technical Abstract: This experiment investigated how season-long, free-choice grazing affected weekly cattle grazing behavior and resource use. Two replicate 24.4-ha grazing enclosures contained four forage types: smooth bromegrass (Bromus inermis), crested wheatgrass (Agropyron desertorum), western wheatgrass (Pascopyrum smithii) and native range. Each forage type was divided into three sub-areas containing either: a water source, a salt block, or forage deferred from use before the experiment (rested). Resource use was tracked in three ways: analysis of aerial photos of the pastures before and after the 3-year study, weekly direct observation of animal use of each area of the pastures, and yearly analysis of forage utilization with clipped plots. As each season progressed, use of smooth bromegrass declined and use of crested wheatgrass and western wheatgrass increased. Use of native range remained relatively constant and low throughout the study. The previously rested sub-areas of the replicate pastures had significantly and substantially more grazing than those with salt or water. Significant auto-correlation in the data was well described by an auto-regressive parameter comprised of the sum of the previous 2 weeks grazing time, which showed gradual shifts in forage preference from one week to the next. Aerial photo analysis supported the findings of the behavioral data; preference between forage types changed over time, and grazing use within pastures was uneven and negatively correlated with salt and water sites. Cattle can rotate themselves among various pasture types if given free- choice; and season-long grazing may be an effective system if a variety of forage types are available.