Beef cattle performance in response to Ipyporã and Marandu brachiariagrass cultivars under rotational stocking management

ABSTRACT The objective of this two-year study was to evaluate live weight gain per animal and per area and their relationships with the characteristics of BRS Ipyporã (Brachiaria ruziziensis × Brachiaria brizantha) and Marandu (Brachiaria brizantha) pastures. A completely randomized block design was used with two treatments and four replicates. The grazing method was rotational stocking, with variable stocking rate. Stocking rate was adjusted twice a week during the grazing period (six or seven days) and post-grazing canopy height target of 15 cm. Animals were weighed every 28 days. Pastures were evaluated pre-grazing to estimate forage accumulation rate, forage mass (FM), leaf (LP) and stem (SP) percentages, and nutritive value. In the post-grazing, FM, LP, and SP were evaluated. Marandu palisadegrass pastures had greater FAR, pre-grazing FM, and hence, a greater SR when compared with BRS Ipyporã. However, compared with Marandu, BRS Ipyporã showed greater LP, leaf:stem ratio, crude protein, and in vitro organic matter digestibility, resulting in greater individual live weight gain. The lesser stocking rate in Ipyporã pastures was compensated, providing a greater individual live weight gain of steers, resulting in a similar live weight gain per area for the two cultivars. Thus, BRS Ipyporã is a good alternative for the diversification of pastures in the Cerrado region.

摘要
本研究为期两年，旨在评估单头家畜增重与单位面积家畜增重水平，及其与BRS Ipyporã（Brachiaria ruziziensis × Brachiaria brizantha）和马兰杜臂形草（Marandu, Brachiaria brizantha）牧场性状的关联。本试验采用完全随机区组设计，设置2个处理、4次重复。放牧方式为可变放牧率的轮牧制度，放牧周期为6~7天，期间每周调整放牧率2次，且设定放牧后冠层高度目标为15 cm。每28天对家畜进行一次称重。放牧前对牧场进行测定，以估算牧草积累速率（forage accumulation rate, FAR）、牧草生物量（forage mass, FM）、叶片占比（leaf percentage, LP）、茎秆占比（stem percentage, SP）及营养价值；放牧后则对FM、LP与SP进行测定。相较于BRS Ipyporã牧场，马兰杜臂形草牧场的FAR与放牧前FM更高，因此其放牧率（stocking rate, SR）也更高。但相较于马兰杜臂形草，BRS Ipyporã的LP、叶茎比、粗蛋白含量与体外有机物消化率更优，进而实现更高的单头家畜增重。Ipyporã牧场较低的放牧率可通过更高的单头肉牛增重得到补偿，最终两个品种的单位面积家畜增重水平相当。因此，BRS Ipyporã是塞拉多（Cerrado）地区牧场多样化种植的优良备选品种。