Dry matter yield, persistence, nutritive value, and in situ dry matter degradability of non-dormant alfalfa (Medicago sativa L.) adapted to Florida

Abstract

Alfalfa (Medicago sativa L.) production in the subtropics may increase forage yield and quality in livestock systems. This study evaluated the effects of seeding rate on dry matter yield (DMY), nutritive value (NV), and in situ degradability of non-dormant alfalfa grown in Florida. The study was designed as a randomized complete block design with a two-way-factorial treatment arrangement with two seeding rates (20 and 27 kg ha⁻¹ of pure live seed) and five genotypes: two breeding lines (UF_AlfPers_2015 and UF_AlfPers_2017) and three cultivars (Florida 77, Florida 99, and Bulldog 805). DMY was assessed between April 2019 and April 2021, and NV and neutral detergent fiber (uNDF) degradability are reported from two harvests, while in situ ruminal dry matter (DM) disappearance was measured for UF_AlfPers_2015 and Bulldog 805 only. Data were analyzed using GLIMMIX in SAS, and mean separation was performed by a Tukey test. No interaction was observed between seeding rate and genotypes for DMY, persistence, and NV. UF_AlfPers_2017 had the highest mean DMY per harvest (1424.5 kg ha⁻¹) and stand persistence (76 plants m⁻²), and Bulldog 805 produced the lowest mean DMY per harvest (936.3 kg ha⁻¹). Bulldog 805 had the lowest lignin concentration, the greatest net energy of lactation, greatest milk per metric ton of forage, and highest NDF degradability. Both the rate and extent of DM degradation were greater for Bulldog 805 compared to UF_AlfPers_2015. The cultivar Bulldog 805 is recommended for planting as it showed greater NV; however, new cultivars and breeding lines are being developed to increase DMY and stand persistence in Florida.