Effects of grazing management in brachiaria grass-forage peanut pastures on canopy structure and forage intake1

Abstract

Maintenance of mixed grass-legume pastures for stand longevity and improved animal utilization is a challenge in warm-season climates. The goal of this study was to assess grazing management on stand persistence, forage intake, and N balance of beef heifers grazing mixed pastures of Brachiaria brizantha and Arachis pintoi. A two-year experiment was carried out in Brazil, where four grazing management were assessed: rest period interrupted at 90%, 95%, and 100% of light interception (LI) and a fixed rest period of 42 days (90LI, 95LI, 100LI, and 42D, respectively). The LI were taken at 50 points at ground level and at five points above the canopy for each paddock using a canopy analyzer. For all treatments, the post-grazing stubble height was 15 cm. Botanical composition and canopy structure characteristics such as canopy height, forage mass, and vertical distribution of the morphological composition were evaluated pre-and post-grazing. Forage chemical composition, intake, and microbial synthesis were also determined. A randomized complete block design was used, considering the season of the year as a repeated measure over time. Grazing management and season were considered fixed, while block and year were considered random effects. In the summer, legume mass accounted for 19% of the canopy at 100LI, which was less than other treatments (a mean of 30%). The 100LI treatment had a greater grass stem mass compared with other treatments. In terms of vertical distribution for 100LI, 38.6% of the stem mass was above the stubble height, greater than the 5.7% for other treatments. The canopy structure limited neutral detergent fiber intake (P = 0.007) at 100LI (1.02% of BW/d), whereas 42D, 90LI, and 95LI treatments had NDF intake close to 1.2% of BW/d. The intake of digestible organic matter (OM; P = 0.007) and the ratio of crude protein/digestible OM (P < 0.001) were less at 100LI in relation to the other treatments. The production of microbial N (P < 0.001) and efficiency of microbial synthesis (P = 0.023) were greater at 95LI and 90LI, followed by 42D and less at 100LI. Overall, the range from 90 to 95% of LI is the recommendation to interrupt the rest period, since this strategy enhanced community stability, forage intake, and nutritional value of the diet. Under on-farm conditions, brachiaria grass and forage peanut pastures should be managed at a range height of 24 to 30 cm.

Managing “Marandu” palisadegrass and calopo pastures based on light interception

“…In light interception experiments, researchers associate LI with the pre-grazing canopy height once canopy height has a high correlation with LI and it is easy to measure in farm conditions (Gomes et al, 2018;Sbrissia & Silva, 2008). In on-farm conditions, we recommend the pre-grazing height of 26 cm that correspond to 95% of LI.…”

Production of beef cattle grazing on Brachiaria brizantha (Marandu grass)—Arachis pintoi (forage peanut cv. Belomonte) mixtures exceeded that on grass monocultures fertilized with 120 kg N/ha

“…It is clear from the results that there was a gradual increase in the proportion of legume in the sward and a concomitant increase in animal performance ( Figure 6). In general, the legume proportion in ruminant diets is proportional to their contribution to the botanical composition (Curll, Wilkins, Snaydon & Shanmugalingam, 1985;Gomes et al, 2018). Thus, a greater legume proportion than of grass resulted in greater nutritive value and improved animal performance.…”

Defoliation frequency affects litter responses and nitrogen excretion by heifers in palisadegrass–forage peanut pastures

“…The botanical composition data (BC; proportion of legume in the herbage mass) used in this study can be found in Gomes et al. (2018).…”