Sward Structure and Herbage Intake Rate of Arachis Pintoi Cv. Belmonte Subjected to Intensities of Grazing.

Grazing management consists in generating adequate grazing conditions through establishment and maintenance sward structure targets that favor high rates of herbage intake. The objective of this experiment was to evaluate the effect of grazing intensity on sward structure and short term herbage intake of Arachis pintoi cv. Belmonte. It was carried out in Piracicaba, SP, Brazil, from February to November, 2013 (autumn, winter and spring). Treatments corresponded to four intensities of grazing characterized by the sward heights of 5, 10, 15 and 20 cm. These were allocated to the experimental units (200 m² paddocks) according to a randomized complete block design, with four replications. The sward structure was determined using the inclined point quadrat method, and the short-term herbage intake rate (STIR) was measured by weighing the heifers at pre and post-grazing, correcting for insensible weight losses during 45-min grazing trials. During these trials the time spent for taking 20 bites was measured and the results used to calculate bite rate (BR). Bite mass (BM) was calculated by the division between STIR and the total number of bites carried out during each grazing trial. Regardless of sward height, the top 50% of the sward vertical profile was comprised of leaf laminae and the bottom 50% comprised of stolons and dead material. Bite mass increased with sward height, with values 3-fold larger recorded on swards managed at 20 cm relative to those managed at 5 cm (1.57 vs 4.61 mg kg body weight^-1), a likely consequence of the deeper leaf layer of swards managed tall. For BR the opposite happened, with higher values recorded on swards managed at 5 and 10 cm relative to those managed at 15 and 20 cm. STIR values were larger on swards managed at 15 and 20 cm during autumn and spring, with no differences between sward heights during winter. BM was the most sensible response variable to variations in sward structure. Maximization of rate of intake was obtained on swards managed at 15 and 20 cm.