Herbage Accumulation and Organic Reserves of Palisadegrass in Response to Grazing Management based on Canopy Targets

Abstract

Improved grazing management can increase the output of many tropical forage–livestock systems. Adjusted grazing management techniques have been proposed for producers that are willing to exploit the growth potential of available forage resources. The objective of this research was to describe and explain variations in herbage accumulation dynamics and organic reserves of cultivar Xaraés palisadegrass [Brachiaria brizantha (Hochst. ex A. Rich.) Stapf syn. Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster] under three grazing managements during spring and summer growing seasons of 2 yr. Pastures were grazed every 28 d (28‐d) or at intervals defined by two levels of pre‐graze canopy light interception (LI). These LI‐based treatments are referred to as “target grazing” (TG) at 95% LI and “delayed grazing” (DG) at ≥ 97.5% LI. Pastures managed using TG and 28‐d showed a similar herbage accumulation rate (HAR) (112 kg DM ha–1 d–1) (P > 0.05), both lesser than DG (141 kg DM ha–1 d–1). Although TG and 28‐d showed similar daily HAR, stem proportion in the stubble was more variable for 28‐d over the growing season. Stem proportion in the stubble was greater for DG (43.8%) and 28‐d (40.4%) than for TG (34.2%). The TG management showed greater total non‐structural carbohydrate (TNC) pools in roots (238 g m–2) than DG (136 g m–2) and 28‐d (199 g m–2), suggesting less dependency of organic reserves. The TG was optimal strategy for intensive grazing management of Xaraés palisadegrass pastures.

Fixed versus variable rest period effects on herbage accumulation and canopy structure of grazed 'Tifton 85' and 'Jiggs' Bermuda grass

“…In the present study, however, the average canopy height related to 95% LI was used as a target management, and the average lenght of grazing cycle was similar to that of pastures managed based on a fixed 28-day rest period. Pedreira et al (2017b) studied 'Xaraés' palisade grass grazed every 28 days, at 95% LI, or 100% LI, and reported that the difference between the rest period of pastures grazed every 28 days and 95% LI was very small, which contributed to similar HAR (112 kg DM ha -1 per day).…”

“…Most of grazing management schemes for intensively managed, improved tropical grasses are based on fixed grazing intervals, often varying from 28 to 42 days during the warm, rainy growing season (Pedreira et al, 2007(Pedreira et al, , 2017bPequeno et al, 2015;. The use of 95% light interception (LI) by the forage canopy has been proposed as the time at which grazing should start (Silva et al, 2009).…”

Herbage responses of Tamani and Quênia guineagrasses to grazing intensity

“…The use of 95% light interception by the forage canopy is recommended as an “optimum” condition for initiation of grazing on intermittently stocked pastures (Pedreira, Silva, Pedreira, & Sollenberger, 2017b). In our study, CP, iNDF and LIG concentrations did not differ between cultivars or grazing intensities and, on average, Quênia had 140, 180, and 25 g kg −1 and Tamani 140, 190, and 27 g kg −1 of the three components, respectively.…”

Canopy characteristics and tillering in \'Zuri\' guineagrass pastures in response to grazing frequency and severity

“…Studies based on structural characteristics of forage grasses are important sources of support for grazing management recommendations. Approaches using "calendar-based" (fixed) rest periods (PEDREIRA et al, 2007(PEDREIRA et al, , 2017PEQUENO et al, 2015;SILVA et al, 2015) is the most common and practical approach for producers. Research, however, has proven that the use of this technique may not optimize many processes and forage characteristics, mainly for species with vigorous stem elongation, resulting in varying forage characteristics through the course of the grazing season PEDREIRA et al, 2017;PEDREIRA et al, 2018).…”

“…The use of canopy light interception (LI) has been proposed to control stem elongation and for making better use of the accumulated herbage allowing it to be harvested with the same structural condition. It has been proposed that canopy LI and canopy height are well enough correlated to allow for this technique to be easily employed by producers (PEDREIRA et al, 2017).…”