Animal performance and sward characteristics of two cultivars of Brachiaria brizantha (BRS Paiaguás and BRS Piatã)

ABSTRACT The objective of the present study was to evaluate live weight gain per animal and per area and its relationship with the characteristics of pastures of Brachiaria brizantha cv. Paiaguás and Piatã. A randomized blocks experimental design was used, with two treatments and six replicates. The experimental area was 8.0 ha, divided into twelve paddocks of 0.67 ha. The grazing method used was continuous stocking, with variable stocking rate. Three tester steers were used per paddock. Sward heights were measured once a week, and the stocking rate (SR) was adjusted using regulator steers to maintain the sward height at 30 cm. Pasture samples were collected once a month, and herbage accumulation rate (HAR), percentage of leaves (PL), leaf:stem ratio (LSR), and nutritive value (NV) were determined. Animals were weighed every 28 days. No differences between the two cultivars were observed during the wet season for any of the evaluated parameters. However, cv. Paiaguás presented higher HAR and, consequently, higher SR than cv. Piatã during the dry season. As a result of its higher regrowth, cv. Paiaguás pastures presented significantly higher PL, LSR, and NV and, consequently, significantly higher average daily live weight gain. These differences resulted in higher live weight gain per area for Paiaguás grass (695 kg/ha per year) than for Piatã grass (645 kg/ha per year). Thus, Brachiaria brizantha cv. Paiaguás is a good alternative to decrease the temporary forage shortage and for the diversification of pastures in the Cerrado biome region.

摘要：本研究旨在评估单头试验动物及单位面积的活体重增重，及其与帕亚瓜斯（cv. Paiaguás）和皮亚塔（cv. Piatã）两个布里赞塔臂形草（Brachiaria brizantha）牧场特征的关联。本实验采用随机区组设计，设置2个处理组，6次重复。实验区域总面积为8.0公顷，划分为12个面积0.67公顷的放牧小区。放牧方式采用连续放牧制度，放牧率可变。每个放牧小区放置3头试验阉牛。每周测定一次草层高度，通过调控阉牛调整放牧率（stocking rate, SR），以维持草层高度稳定在30 cm。每月采集牧场样品，测定牧草积累速率（herbage accumulation rate, HAR）、叶片占比（percentage of leaves, PL）、叶茎比（leaf:stem ratio, LSR）及营养价值（nutritive value, NV）。每28天对试验动物进行一次称重。在湿季，两个栽培品种的所有测定参数均无显著差异。但在旱季，帕亚瓜斯栽培品种的牧草积累速率更高，因此其放牧率也高于皮亚塔栽培品种。由于其更强的再生能力，帕亚瓜斯牧场的叶片占比、叶茎比及营养价值均显著更高，因此平均日活体重增重也显著提升。上述差异使得帕亚瓜斯臂形草的单位面积活体重年增重可达695 kg/ha，高于皮亚塔臂形草的645 kg/ha。综上，布里赞塔臂形草（Brachiaria brizantha）帕亚瓜斯栽培品种可作为缓解塞拉多生物群系区域暂时性牧草短缺及实现牧场多样化的优良方案。