INFLUENCE OF SUPPLEMENTATION ON BEHAVIOR OF GRAZING CATTLE

Dormant grasses are usually deficient in nutrients needed to meet cattle requirements. Research results indicate that grazing activities are sensitive to some environmental variables and vegetative (sward) characteristics; however, minimal information is available on the influence of supplementation regimens on cattle grazing activities. Supplementation studies reviewed had forage N levels that ranged from .9 to 1.2% and forage intakes that ranged from 12.3 to 31.0 g of OM/kg of BW. Protein supplementation affected (P < .05) time spent grazing: unsupplemented (NS) cattle grazed approximately 1.5 h/d more than did supplemented (S) cattle. Type of supplemental protein and time of daily feeding did not affect (P > .10) this response. Different types and timing of starch-based supplements produced variable results; however increasing the level of supplemental starch decreased (P < .05) daily grazing time. Protein supplementation increased (P < .05) harvesting efficiency (HE; grams of forage intake.kilogram of BW-1.minute spent grazing-1); however, high-starch supplements either did not alter (P > .10) or decreased (P < .05) HE compared with NS. Progressive defoliation can influence grazing behavior in both sheep and cattle grazing actively growing forage; however, evaluation of vegetative characteristics of dormant forage and the corresponding effect on grazing behavior are not known. The effects of various grazing management strategies on cattle behavior are inconclusive and deserve additional attention. Methods and(or) management practices that modify behaviors to control feed intake, improve efficiency, or reduce stress could be major contributions to the livestock industry.