GrazeIn: a model of herbage intake and milk production for grazing dairy cows. 1. Prediction of intake capacity, voluntary intake and milk production during lactation

Abstract

The prediction of both food intake and milk production constitutes a major issue in ruminants. This article presents a model predicting voluntary dry matter intake and milk production by lactating cows fed indoors. This model, with an extension to predict herbage intake at grazing presented in a second article, is used in the Grazemore decision support system. The model is largely based on the INRA fill unit system, consisting of predicting separately the intake capacity of the cows and the fill value (ingestibility) of each feed. The intake capacity model considers potential milk production as a key component of voluntary feed intake. This potential milk production represents the energy requirement of the mammary gland, adjusted by protein supply when the protein availability is limiting. Actual milk production is predicted from the potential milk production and from the nutritional status of the cow. The law of response of milk production is a function of the difference between energy demand and actual energy intake, modulated by protein intake level. The simulation of experimental data from different feeding trials illustrates the performance of the model. This new model enables dynamic simulations of intake and milk production sensitive to feeding management during the whole lactation period.

Development and evaluation of the herd dynamic milk model with focus on the individual cow component

“…Herd feeding and dairy cow performance The model incorporates the French feeding system (Faverdin et al, 2010;Faverdin et al, 2011), which was modified to integrate milk production, BCS and BCS change of animals. In this paper, the milk output from the model is expressed in kilogram of standard milk (MY) at 4.0% of fat and 3.1% of protein content, corresponding to the equation of Faverdin et al (2010) (Supplementary Equation S12).…”

“…The INRA (Institut National de la Recherche Agronomique) feeding system (INRA, 2010) was selected to model the nutrient intake within the model. The intake when housed and at grazing is calculated based on the GrazeIn model as described in Delagarde et al (2011aand 2011b), Faverdin et al (2011. In simple terms, intake of the animal is the lesser of the intake permitted by the intake capacity and fill value (FV) of the feed, the HA and the intake needed to meet the requirements.…”

“…The quality of the forage or grass is characterised by its energy value (unité fouragère lait (UFL)), protein (protéine digestible dans l'intestin (PDI)) and FV. The FV of a forage is an inverse function of its ingestibility and is calculated by the ratio of intake of the reference forage to voluntary dry matter intake of the considered forage (Faverdin et al, 2011). The quality of the concentrate is determined by its UFL and PDI.…”

“…Having a model that can react in a meaningful way across these different questions allows farmers to optimise their decision-making process continually. For example, when feeding the dairy cow, predicting the partition between milk production and body condition score (BCS) change throughout lactation either in grazing or indoor feeding would allow better decisions to be made on farm but these challenges present a major obstacle for modellers all over the world (Friggens et al, 2004;Faverdin et al, 2011;Baudracco et al, 2012). The model presented here deals with this issue in a grazing context.…”

“…The statistical analyses used were the concordance correlation coefficient (CCC) and the relative prediction error (RPE) to evaluate the daily herbage dry matter intake, the milk yield (MY) and live weight change. The milk production and herbage intake of the French model GrazIN (Delagarde et al, 2011a;Faverdin et al, 2011) was validated by comparing model outputs against experimental data using the mean square prediction error on 206 experimental herds (Delagarde et al, 2011b).…”