Herbage intake by steers grazing in a natural grassland with predominance of Andropogon lateralis Nees managed under different canopy heights

Ricardo Biasiolo,Cassiano Eduardo Pinto,Tiago Celso Baldissera,Henrique Mendonça Nunes Ribeiro-Filho,Pablo Giliard Zanella,Cássio Felipe Lopes,Fabio Cervo Garagorry,Artur Martins Barbosa

doi:10.1590/0103-8478cr20200696

Abstract

ABSTRACT: The animal performance on pasture is directly correlated to canopy structure since this influences the herbage consumption. This study was evaluated the effects of four pre-grazing canopy heights (12, 20, 28 and 36 cm) of Andropogon lateralis Ness on herbage intake and feeding behavior of steers in a natural grassland under intermittent stocking management, using the same proportion of defoliation (40% reduction in pre-grazing height, i.e., post-grazing heights of 7.2, 12.0, 16.8 and 21.6 cm). The experiment was conducted on a total area of 14,000 m2, divided into sixteen paddocks of 875 m2. Thirty-two steers were used, divided into uniform pairs according to the live weight (LW) at the start of the experiment (244 ± 23.0 kg). Each paddock was subdivided into three plots of identical area; the first two plots were used for the adaptation period and the third for the assessment period. A randomized block design was used with four replicates and two assessment periods. Herbage mass and neutral detergent fiber content increased linearly (P < 0,001) with the increase of pre-grazing canopy heights. In contrast, was not affected by treatments, with mean values of 75 g/kg of dry matter (DM) in the upper stratum and 83 g/kg of DM in lower stratum. The herbage intake was similar between treatments (P = 0.255), averaging 1.78% LW. Grazing time increased linearly in the upper stratum and decreased linearly in the lower stratum with increasing pre-grazing canopy heights. Total time spent grazing, ruminating, and idling did not differ between treatments, with means of 52.6%, 23.0%, and 24.2%, respectively. Pre-grazing canopy heights treatments, based on the predominant species A. lateralis, did not affect the daily herbage intake of steers.

Highlights

Natural grasslands can be characterized as natural pastoral biosystems and their exploitation using livestock represents one of the best forms of sustainable land use (TILMAN et al, 1996; CARVALHO & BATELLO, 2009)
Canopy structure The pre-grazing canopy heights of the upper stratum were reached according to the goals foreseen for the corresponding treatments, while the heights of the lower stratum increased linearly as the pre-grazing canopy heights increased (P
The herbage intake estimated with the Pampa Corte model, based on the bromatological composition of the upper and lower strata, decreased linearly with the increase in pregrazing canopy heights (Table 2)

Summary

Introduction

Natural grasslands can be characterized as natural pastoral biosystems and their exploitation using livestock represents one of the best forms of sustainable land use (TILMAN et al, 1996; CARVALHO & BATELLO, 2009). When grazed, these environments tend to create a canopy structure. Andropogon lateralis Ness (Poaceae) is one of the most important species of the upper stratum of natural grasslands from southern Brazil (GOMES et al, 1990; BOLDRINI, 2002) This is a perennial tussock-forming species, greenish-gray color, and feathery inflorescences (ARAÚJO, 1971). A. lateralisis is highly rustic and resistant to frosts, fire, trampling, and grazing (HERVÉ & VALLS, 1980; TRINDADE & ROCHA, 2002)

Methods

Results

Conclusion