Validation of Predictive Equations of Pre‐Harvest Forage Nutritive Value for Alfalfa–Grass Mixtures

Abstract

CORE IDEAS: Predictive equations can help producers determine when to harvest their forage fields.Equations developed in New York State could be used to predict aNDFom, ADFom, RFV, and RFQ in Quebec.Equations developed in New York State cannot be used to predict NDFdom in Quebec. Predictive equations of pre‐harvest nutritive attributes of alfalfa (Medicago sativa L.)–grass mixtures using simple plant or climate data were developed in New York State for the spring growth, but they must be validated before being used outside their development area. Our objective was to validate these predictive equations for their use in Quebec, Canada. Samples (n = 679) of alfalfa–grass mixtures were collected during spring growth at three sites for 2 consecutive years and analyzed for several nutritive attributes. Alfalfa maximum height, the most mature stage of development of alfalfa, growing degree days, grass proportion, and grass maximum height were also measured and used as input in several existing predictive equations. Predicted values were then compared with laboratory‐determined values using several validation statistics. The most promising predictive equations of neutral detergent fiber (NDF) and acid detergent fiber concentrations, relative feed value, and relative forage quality had coefficients of determination (r²) of the linear regression between observed and predicted values between 0.74 and 0.81, and an index of agreement (d) between 0.87 and 0.93. Several equations were, however, significantly biased as indicated by slopes and intercepts of the regressions. The NDF digestibility was not predicted satisfactorily with the New York State equations. Among all equations evaluated, an equation for NDF concentration has the most potential for use to predict the spring growth pre‐harvest nutritive value of alfalfa–grass mixtures in Quebec.

Plant phenotyping relevance

アルファルファ・イネ科混播の収穫前栄養価を予測する既存方程式を、植物形質・気候データと実測値で体系的に検証しており、予測手法の検証が研究の中心である。

Code and data availability

The supplied blocks describe field sampling of 832 alfalfa–grass forage samples, VNIRS chemical analyses, and SAS regression validation of NYPEAQ equations, but contain no data availability statement, public dataset deposit, author code release, or supplement with phenotyping data. The only URLs present are the article

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