Sward Structural Characteristics and Performance of Beef Heifers Reared under Rotational Grazing Management on Campos Grassland

Abstract

This study aimed to evaluate the effect of two rest intervals on structural sward characteristics and productive performance of beef heifers reared on Campos grassland managed on rotational grazing. The treatments were two intervals between grazing of 375 and 750 DD (degree days), based on thermal cumulative sum for leaf expansion of native grasses belonging to two functional groups. The experimental design was a randomized complete block design with two treatments and three replications. The tested animals were beef heifers with initial age of 12 months and average weight of 185.2 ± 17.4 kg. Measures in the pasture were: herbage mass, mass of green leaf blades, stem mass, dead material mass and green leaf allowance. The 750 DD rest interval presented higher herbage mass (24%), higher green herbage mass and 19% more leaves in the canopy. This rest interval also presents a high proportion of dead material and stems in the sward structure. In the other way, the 375 DD rest interval presents better chemical characteristics, with 20% more crude protein in the hand plucking samples. Heifers' dry matter intake was similar between the rest intervals (2.04% of live weight) and the bite mass was also similar (0.22 g DM per bite) but the animal performance was higher in the 375 DD rest interval. The stocking density showed similarity between treatments with an average of 875 kg/LW/ha. The live weight gain per area was higher in 40 kg/LW/ha (P = 0.117) for 375 DD rest interval, reaching 251 kg/LW/ha produced over the 149 experimental days. Based on these results, we can conclude that the treatment of shortest interval between defoliation gave the highest gain individual animals in warm seasons.

Timing and Duration of Observation Periods of Foraging Behavior in Natural Grasslands

“…The blocking criterion was the relief. Details regarding management can be found in Barbieri et al ( 10 ).…”

“…For example, ruminants commonly have grazing times between 450 and 600 min/day in temperate pastures and rarely forage <360 min/day, with times that may exceed 760 min/day on subtropical and tropical pastures ( 4 , 5 ). In the southern Brazil Campos grasslands ( 6 ), without limitations to inhibit potential intake (e.g., sward height or herbage mass), the time spent grazing commonly ranges between 500 and 650 min/day ( 7 – 9 ), regardless of the grazing method used ( 10 ). This variation in grazing time indicates potentially diverse situations and challenges that animals can face, even in situations with abundant forage allowance, attesting to the complex interaction of animals with plants and sward structure.…”

Beef heifers grazing behavior and herbage intake in natural grassland under rotational grazing

“…Recent research results have shown that the potential productivity of this management goes far beyond of what is usually recorded at commercial farms, making possible to obtain animal performance necessary to achieve 65 to 70% of adult weight, a goal for mating at 24 months of age (QUADROS et al, 2011;BARBIERI et al, 2014). Nevertheless, the influence of this management proposal (rotational grazing with rest intervals according to morphogenetic traits) on animal's behavior is not already explored.…”

Leaf tissue fluxes of Pampa biome native grasses submitted to two grazing intervals

“…() reported an average daily gain of approximately 0·28 and 0·18 kg for heifers reared on this natural grassland managed with grazing interval of 375 and 750 DD respectively. In the same area and with the same grazing protocol, heifers with similar BW, and with 0·36 kg per day liveweight gain, have an estimated dry‐matter intake of 2·04% of their BW (Barbieri et al ., ). Thus, it follows that these heifers, with an average DM intake of leaf blade equivalent to 1·40% of their BW, obtained nearly 68% of their daily DM intake consisting of leaves from the five studied grasses.…”