摘要
There is little information about whether the increased secondary productivity observed in pastures fertilized with high nitrogen rates is attributable to fluctuations in the nutritional value or pasture structural characteristics, or both. This study aimed to identify a set of factors (structural and nutritional characteristics) that best explain the performance of beef steers grazing Mombasa grass pastures under residual effects of nitrogen fertilizer. The data were collected in Mombasa grass pastures fertilized with increasing rates of nitrogen (N) (100, 200 and 300 kg ha-1) from 2015 to 2017. In 2018, nitrogen fertilization was not used in order to characterize a residual effect of the nutrient. Variables related to pasture structural characteristics such as forage accumulation rate (FAR), canopy height, forage mass (FM) and morphological components were evaluated. The study also evaluated the nutritional value of leaf blades and the performance of beef steers based on average daily gain (ADG) and stocking rate. Principal component analysis was performed using the dataset available. Most of the variance (99.6%) was explained by only two principal components (PCs), of which 90.0% corresponded to PC1. The most influential parameters for PC1, in order of priority, were: FAR, FM, leaf blade and stem masses. These variables were positively associated with stocking rate. Conversely, ADG was not associated with any variable. ADG was the most relevant variable for the second PC; however, this PC explained less variance (9.6%). The structural characteristics of the pasture (FAR, FM and morphological components mass) better explain the fluctuations in the performance of cattle on pastures of Mombasa grass under residual effects of nitrogen fertilizer. The stocking rate is an efficient parameter to support decision-making in managed pastures with variable stocking.
摘要译文
几乎没有关于在高氮肥水平的牧场中观察到的次级生产力提高的原因是营养价值或牧场结构特征的波动，还是两者都有。本研究旨在确定一组因素（结构和营养特性），这些因素可以最好地解释在氮肥残留影响下放牧蒙巴萨草场的牛ste的性能。数据收集自2015年至2017年随着氮（N）浓度（100、200和300 kg ha-1）增加而施肥的蒙巴萨草场。2018年，未使用氮肥来表征该草的残留效应。养分。评估了与牧场结构特征有关的变量，例如草料积累率（FAR），冠层高度，草料质量（FM）和形态成分。研究还根据平均日增重和放养率评估了叶片的营养价值和牛ste的性能。使用可用的数据集进行主成分分析。大部分差异（99.6％）仅由两个主成分（PC）解释，其中90.0％对应于PC1。按优先顺序，对PC1最具影响力的参数是：FAR，FM，叶片和茎质量。这些变量与放养率成正相关。相反，ADG没有与任何变量关联。 ADG是第二台PC最相关的变量；但是，该PC解释的差异较小（9.6％）。牧场的结构特征（FAR，FM和形态成分质量）可以更好地解释在氮肥残留效应下蒙巴萨草场上牛的生长性能波动。放养率是支持决策的有效参数，可以在具有可变放养的托管牧场中进行。
GURGEL; Antonio Le;ro Chaves et al.. Principal component analysis of steers performance and structural and nutritional characteristics of Mombasa grass.[J]. Ciencia Rural, 2021,51(1)