162 Nutritive value and dry matter yield of stockpiled tall fescue across plant hardiness zones 7 and 8

Abstract

Abstract Pastures in Tennessee comprise mainly tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.], a cool-season perennial grass. Given that producers in Tennessee feed hay for an average of 143 d per year, there is interest in utilizing the practice of stockpiling to extend the grazing season. Although this practice has been proven to reduce hay needs (Freeman et al., 2019), it is vital to maintain up-to-date recommendations using data from across the southeastern US to inform grazing decisions. The objective of this study was to determine the nutritive value and dry matter yield of stockpiled tall fescue across plant hardiness zones 7 and 8. Fourteen farms across Tennessee and Alabama were identified as sampling sites. In September 2021, three exclusion cages (1.3 m × 1.3 m) were constructed at each site, forage was clipped to a 5-cm height, and plots were fertilized at a rate of 67 kg N/ha. During years 2021-2022 and 2022-2023, samples were clipped at a 5-cm height from a 0.1-m2 quadrat monthly from October through February. Samples were collected from a different location within the plot each month to ensure there was no overlap. Samples were dried and weighed to determine dry matter yield and then ground for NIRS analysis to determine nutritive value. Data were analyzed using PROC GLIMMIX for a completely randomized design. Independent variables were stockpile period length and plant hardiness zone. Results indicate that plant hardiness zone did not have a significant effect on forage yield (P = 0.2098). Dry matter yield increased over the length of the stockpiling period (P < 0.0001) from 2,637 to 4,922 kg DM/ha. Crude protein (CP) and total digestible nutrients (TDN) concentrations decreased (P < 0.0001 and P = 0.0358, respectively) throughout the stockpiling period; however, ranges were still within those needed to support the nutritional needs of a lactating cow with CP ranging from 15 to 17% and TDN ranging from 68 to 70%. As expected, neutral detergent fiber (NDF) and acid detergent fiber (ADF) concentrations increased over the stockpiling period (P = 0.0029 and P = 0.0145, respectively) as plants matures. There were no significant changes in ash and fat concentrations due to stockpiling length. Results from this study conclude that stockpiled tall fescue in plant hardiness zones 7 and 8 can support the nutritional requirements of mature cows at all stages of production through the winter months. Results will be used to inform Extension recommendations to assist producers in making management decisions that increase grazing days and reduce supplemental feed input costs.