Principal component analysis of steers performance and structural and nutritional characteristics of Mombasa grass

Antonio Leandro Chaves Gurgel,Juliana Caroline Santos Santana,Denise Baptaglin Montagner,Valeria Pacheco Batista Euclides,Gelson Dos Santos Difante,Alexandre Romeiro De Araujo

doi:10.1590/0103-8478cr20200306

Antonio Leandro Chaves Gurgel, Juliana Caroline Santos Santana + Show 4 more

Open Access

https://doi.org/10.1590/0103-8478cr20200306

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Abstract

ABSTRACT: 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.

Highlights

The productivity of pastures depends on both individual animal performance and stocking rate (DIFANTE et al, 2010; EUCLIDES et al, 2017)
Qualitative modifications can lead to different outcomes in animal production, for this reason it is necessary to recognize the extension of the effect of the increase in secondary productivity observed in pastures fertilized with high nitrogen rates, identifying whether its performance is limited to the greater in the fluctuation of the nutritional value or in the structural characteristics of the pasture, or both
An effective way to validate these responses is through principal component analysis (PCA)

Summary

Introduction

The productivity of pastures depends on both individual animal performance and stocking rate (DIFANTE et al, 2010; EUCLIDES et al, 2017). An effective way to validate these responses is through principal component analysis (PCA) This analysis seeks, based on a large number of original correlated characteristics, to obtain linear combinations of these characteristics, known as principal components, in such a way that the correlation between these variables is null (DA SILVA & SBRISSIA, 2010; OLIVEIRA et al, 2019). This type of analysis has the potential to be applied in the interpretation of data on forage plants (DA SILVA & SBRISSIA, 2010)

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