Tall fescue sward structure affects the grazing process of sheep

Abstract

The study of factors influencing animal intake can provide a better understanding of the dynamics of the pasture ecosystem and serve as a basis for managing livestock in a more efficient way. We measured different sward surface heights of tall fescue in the process of short-term intake rate of sheep. There was a significant effect of sward surface height on herbage mass ( P < 0.001), leaf lamina mass ( P < 0.001), other species mass ( P = 0.02), bite mass ( P = 0.01) and short-term intake rate ( P = 0.03) of sheep. There was a quadratic fit between time per bite and bite mass ( P = 0.006). Multivariate analysis showed that the short-term intake rate and bite mass were positively correlated (r = 0.97), bite rate and total jaw movement rate were positively correlated but both were negatively correlated with time per bite. The sward surface height of tall fescue corresponding to the maximum short-term herbage intake rate was 22.3 cm. The underlying processes were driven by the bite mass, which was influenced by the leaf lamina bulk density and its consequences upon time per bite. This sward surface height can be adopted as a pre-grazing target for rotational stocking systems to optimize sheep nutrition on pastures.

Reconciling the Plant-Animal Interface: Convergence of Optimal Herbage Accumulation and Intake Rate by Sheep Grazing Tall Fescue

“…It is based on the optimal foraging theory that states maximization of the intake rate of energy over the grazing process through decisions within different space-time scales (Charnov 1976;Pyke et al 1977). The results of Szymczak et al (2020b) agreed with studies that demonstrated intermediate SSH at the STIR − max for other forage species (Fonseca et al 2012;Mezzalira et al 2014;Silva et al 2017). These nding have implications at the plant-animal interface.…”

“…A study conducted by Szymczak et al (2020b) in the same experimental area as this one (same area, experimental and climate conditions and forage species), demonstrated a signi cant effect of tall fescue SSH on STIR of sheep. There was a quadratic response of STIR to SSH, increasing up to a SSH of 22.3 cm (y = 5.61 g DM min − 1 ) and decreasing at taller SSH (Fig.…”

“…In this report, we relate the patterns of herbage accumulation to bite mass (BM) and STIR by sheep grazing various SSH levels in the same experimental pasture area, which previously reported in detail by Szymczak et al (2020b). Brie y, STIR was determined by calculating intake rate of sheep at various SSH levels using pre-and post-grazing animal weights corrected for insensible weight losses, insensible time loss, and effective eating time.…”

“…Using pre-grazing SSH of 22.3 cm (Szymczak et al 2020b) as a management target in rotational stocking, there may be optimization of e ciency in use of light and nitrogen, tillering rate, carbon balance, and leaf appearance rate. This also may promote less instantaneous senescent material and an increase in the vegetative period of the forage in relation to the highest SSH (Evers et al 2007a;Gastal and Lemaire 2002;Nelson 2000).…”

“…The purpose of this study was to evaluate the optimal point for grazing management from the plant and animal perspective, through the adjustment of instantaneous herbage accumulation rate by the Gompertz curve, proposed by Barker et al (2010), and the maximum short-term intake rate, obtained in the study of Szymczak et al (2020b), using Schedonorus arundinaceus [Schreb.] Dumort (tall fescue) as the model system.…”