Abstract
The objective of this study was to evaluate the Brachiaria brizantha cv. Marandu canopy structure maintained at different grazing heights under a continuous stocking rate and with a dietary supplementation strategy for the animals during the rainy season. This study also intended to observe the relationships of these variables with the grazing behaviors of the heifers. The effects of three canopy heights (15, 25 and 35 cm) were evaluated in association with three types of supplements: one mineral and two protein/energy supplements, the first with a high rumen degradable protein and energy and the others with a low ratio. Both the protein/energy supplements were provided at 0.3% of body weight/day. The experimental design was completely randomized, with two replications and repeated measures, and took place during the period from January to April 2008. The supplementation strategies did not affect any variable related to the canopy structure. Total and green herbage masses and the ratio of green/dead material increased with canopy height. The leaf/stem ratio was higher in the lowest canopy height: 15 cm. Changes in the canopy structure caused variations in the grazing behavior of the animals. Animals maintained in the 15-cm-tall pasture grazed for a longer time, increasing the time for each meal, but the number of meals was lower than that of the animals grazing within the 35-cm-tall pasture. The grazing time of animals receiving the energy/protein supplement was lower only in the period of the day during which it was supplied. Canopy structure is affected by sward height, and changes animal behavior. Supplementation does not affect the canopy structure of the pastures with similar heights.
Highlights
In pasture production systems, issues related to plantanimal interactions are of great importance for the success of the activity
The experiment was conducted in the forage experimental sector of the Departamento de Zootecnia at FCAV/UNESP, Jaboticabal, São Paulo, located at 21°15’22" south latitude, 48o18’58" west longitude and 595 m altitude
The experiment was installed in a pasture area of Brachiaria brizantha
Summary
Issues related to plantanimal interactions are of great importance for the success of the activity. In this scenario, it is very important to understand the limits of the resistance and tolerance of forage plants to the animals’ grazing action. The objective of using nutritional supplements is to increase animal performance, variations in pasture structure are often observed (Gomide et al, 2009; Bremm et al, 2008) as stocking rates increase (Roman et al, 2008), as a consequence of the substitutive or combined effects of supplementation, depending on the criteria adopted for regulating the management of animal stocking. The structure of the pasture has a strong effect on the
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