Factors Affecting Sugar Accumulation and Fluxes in Warm- and Cool-Season Forages Grown in a Silvopastoral System

Valens Niyigena,Christine Nieman,Kenneth P Coffey,Mohan Acharya,Dirk Philipp,Lillian Meadors,Amanda J Ashworth,Thomas J Sauer

doi:10.3390/agronomy11020354

Abstract

Forage management and environmental conditions affect water soluble carbohydrate (WSC) storage, and, in turn, influence ruminant forage utilization in silvopastoral systems. The objective was to determine effects of four dependent variables: forage species [(non-native, C3 (orchardgrass (Dactylis glomerata L.)) and native C4 mix (8:1:1 big bluestem (Andropogon gerardii Vitman), little bluestem (Schizachyrium scoparium Michx. Nash) and indiangrass (Sorghastrum nutans L.))]; fertility (poultry litter and an unfertilized control); forage sampling date (mid-May, late-May, early-June, mid-June, and late-June); and hour of day (0800, 1100, 1400, and 1700 h) on WSC accumulation in a silvopasture. Concentrations of WSC (g kg DM−1) were greater (p ≤ 0.05) for C3 forages, with poultry litter not impacting WSC accumulation. Overall, WSC was greatest in mid-June, with the lowest WSC concentration observed at 0800 compared to 1100, 1400, and 1700 h (p ≤ 0.05). Therefore, harvesting forages later in the day resulted in greater WSC. A stepwise regression model indicated acid detergent fiber, ash, and forage P concentration were the best predictors (R2 = 0.85, p ≤ 0.05) of forage WSC. These results may be useful in future studies aimed at explaining diurnal cattle grazing preference and optimum forage harvest timing in silvopastoral systems.

Highlights

In silvopastures, or the integration of trees and livestock in one system, appropriate management of trees and pasture is critical to ensure complementary productivity
In order to advance our understanding of factors affecting water soluble carbohydrate (WSC) accumulation and fluxes in forages, this study aims to evaluate: (i) differences in WSC accumulation in C3 and C4 grasses; (ii) how fertility impacts forage WSC; (iii) diurnal and seasonal fluctuations for C3 and C4 forages, fertilized and un-fertilized; and (iv) correlations between forage nutrient content parameters and WSC concentrations in a silvopastoral system
Our results suggest a WSC increase of 26 g kg dry matter (DM)−1 from 800 to 1700 h

Summary

Introduction

The integration of trees and livestock in one system, appropriate management of trees and pasture is critical to ensure complementary productivity. Forage management is important for increasing forage nutrient composition and ensuring high forage utilization by grazing animals. Investigations into potential factors affecting WSC concentration in forages, such as forage species, fertilization, and seasonal and diurnal variations are necessary to better understand forage utilization by grazing livestock in silvopasture systems. Integrating both cool- and warm-season forages in silvopastoral systems may be advantageous to livestock producers because of the contrasting seasonal growth patterns. C3 grasses reportedly have greater concentrations of WSC than C4; WSC in both

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Conclusion