Plant Persistence and Animal Performance for Continuously Stocked Alfalfa Pastures at Three Forage Allowances

Abstract

Alfalfa (Medicago sativa L.) has not been well suited for pasture because of its intolerance to grazing. 'Alfagraze', a cultivar bred for grazing tolerance, offers potential to use alfalfa as pasture. A 3-yr grazing study was initiated in central Georgia to investigate persistence and animal performance of 'Apollo' and Alfagraze alfalfa at low, medium, and high forage allowance (FA). The FA for this study were targeted at 1000, 2000, and 3000 lb dry matter (DM)/1100 lb animal unit for low, medium, and high FA, respectively. Low FA reduced stand of both cultivars (P < 0.05) after only 1 yr (low = 6.8, medium = 8.2, high = 8.8 plants/sq ft). After 2 yr, high FA paddocks averaged 8.6 plants/sq ft, while medium and low FA had decreased to 5.4 and 4.4 plants/sq ft, respectively. The difference in grazing tolerance between cultivars became evident after 2 yr of grazing, when, averaged across FA, Alfagraze had 7.3 plants/sq ft and Apollo had 5.0 plants/sq ft. After an additional year of continuous stocking, Alfagraze had approximately 150% more plants than Apollo. Persistence differences between cultivars were most evident at low FA. After 2 yr of low FA, Alfagraze had 5.5 and Apollo had 3.3 plants/sq ft. After 3 yr, Alfagraze maintained stands of 5.5 plants/sq ft, while Apollo stands decreased to 1.5 plants/sq ft. Lower FA resulted in greater bermudagrass [Cynodon dactylon (L.) Pers.] encroachment. Lower FA decreased average daily gain (ADG) in yr 1. At low FA, improved persistence of Alfagraze resulted in 0.45 Ib/d higher ADG than Apollo in yr 2. The better grazing-tolerance of Alfagraze alfalfa resulted in longer stand persistence and better animal performance.