Evaluation of Warm-Season Annuals for Livestock Production

Abstract

Warm-season forages are high yielding and can have high nutritive value, providing producers with an ideal option during the months in which cool-season forages are not productive. Two, 2-year small plot studies were completed to evaluate the forage mass and nutritive value of warm-season annual forages. Study 1 evaluated sorghum × sudangrass [(Sorghum bicolor L. Moench) × (Sorghum × drummondii)], cowpea (Vigna unguiculata L. Walp), and crabgrass (Digitaria sanguinalis L.), in mono-, bi-, and tri mixtures, as well as sorghum × sudangrass with an insecticide at E.V. Smith Research and Extension Center (Headland, AL). Plots containing sorghum × sudangrass were also evaluated for sugarcane aphid [SCA; Melanaphis sacchari (Zehntner)] infestations on a weekly basis. Forage mass (FM) was not different between treatments and ranged from 1038 to 2358 kg/ha. Crude protein (CP) concentration in both years was greater (P ≤ 0.02) in cowpea than all treatments except sorghum × sudangrass + cowpea (P = 0.06) in year 2 and cowpea + crabgrass (P ≥ 0.24) in both years. Concentrations of CP ranged from 6.6 to 16.6%. Neutral detergent fiber (NDF) ranged from 47.4 to 67.7%. In year 1, NDF was less (P = 0.02) in cowpea and cowpea + crabgrass than sorghum × sudangrass + insecticide and sorghum × sudangrass + crabgrass, and in year 2, cowpea and cowpea + crabgrass were less (P ≤ 0.01) than all treatments except sorghum × sudangrass + cowpea (P ≥ 0.16). Acid detergent fiber (ADF) was not different between treatments and ranged from 16.5 to 39.6%. Mixing sorghum × sudangrass with other forage species increased incidence of SCA per leaf. The warm-season annual forages used in this study showed promise for use as forage; however, insecticide use may be recommended when using sorghum × sudangrass. Study 2 evaluated FM, nutritive value and persistence of 5 soybean cultivars (‘Stonewall’, ‘Laredo’, ‘Tower of Leaves’, Asgrow® ‘AG64X8’, and Asgrow® ‘AG79X9’) at two locations in two growing seasons under two management strategies (row spacing and stubble height). Years and location did vary, but overall Stonewall consistently had the highest FM with high nutritive value. Tower of Leaves had high FM but had lower nutritive value the Stonewall. The grain cultivars (AG64X8 and AG79X9) had high crude protein, but otherwise were inconsistent in nutritive value and had moderate FM. Laredo consistently had the lowest FM. Lower stubble heights resulted in increased FM but decreased nutritive value. Row spacing did not consistently influence either FM or nutritive values. Due to the high nutritive value and FM, Stonewall should be evaluated alone and in mixtures with other summer annual forages for inclusion in livestock diets.