Publication Date

1997

Location

Manitoba and Saskatchewan

Description

Grazing efficiency and livestock performance were compared on swards rotationally grazed down to either 50 or 100 mm for three years. With a fixed entry height of 200-250 mm, standing swards of mixed grasses and white clover (Trifolium repens L.) were stratified into 50 mm vertical layers both pre- and post-grazing. Through four or five cycles of grazing each year for three years, a fixed entry height range stabilized total standing herbage at 3250 to 3690 kg OM ha-1. Organic matter on-offer above 100 mm was 36, 45, and 43% of total standing herbage in the three years, compared with 60, 66, and 62% above 50 mm. Lowering residual height from 100 to 50 mm increased percentage disappearance of total standing herbage from 44, 44, and 48% at 100 mm to 60, 61, and 62% at the 50 mm residual. Grazing to the lower residual increased utilization efficiency by about 35%, but did so at the expense of individual animal intake. Daily OM intake was 2.8, 2.7, and 2.9% of bodyweight in the 100 mm residual, but declined to 2.2, 1.9, and 2.1% when stock were obliged to graze down to a 50 mm residual. The homogeneity of IVOMD above 50 mm suggests that reduced rate of intake in the 50- 100 mm layer resulted from factors other than quality, such as difficulty of prehension or avoidance of soiled herbage.

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Applications of Height-Based Grazing Management in Mixed Swards

Manitoba and Saskatchewan

Grazing efficiency and livestock performance were compared on swards rotationally grazed down to either 50 or 100 mm for three years. With a fixed entry height of 200-250 mm, standing swards of mixed grasses and white clover (Trifolium repens L.) were stratified into 50 mm vertical layers both pre- and post-grazing. Through four or five cycles of grazing each year for three years, a fixed entry height range stabilized total standing herbage at 3250 to 3690 kg OM ha-1. Organic matter on-offer above 100 mm was 36, 45, and 43% of total standing herbage in the three years, compared with 60, 66, and 62% above 50 mm. Lowering residual height from 100 to 50 mm increased percentage disappearance of total standing herbage from 44, 44, and 48% at 100 mm to 60, 61, and 62% at the 50 mm residual. Grazing to the lower residual increased utilization efficiency by about 35%, but did so at the expense of individual animal intake. Daily OM intake was 2.8, 2.7, and 2.9% of bodyweight in the 100 mm residual, but declined to 2.2, 1.9, and 2.1% when stock were obliged to graze down to a 50 mm residual. The homogeneity of IVOMD above 50 mm suggests that reduced rate of intake in the 50- 100 mm layer resulted from factors other than quality, such as difficulty of prehension or avoidance of soiled herbage.