title: Development and evaluation of the herd dynamic milk model with focus on the individual cow component.
abstract: The herd dynamic milk (HDM) model is a dynamic model capable of simulating the performance of individual dairy animals (from birth to death), with a daily time step. Within this study, the HDM model is described and evaluated in relation to milk production, body condition score (BCS) and BCS change throughout lactation by comparing model simulations against data from published experimental studies. The model's response to variation in genetic potential, herbage allowance and concentrate supplementation was tested in a sensitivity analysis. Data from experiments in Ireland and France over a 3-year period (2009-11) were used to complete the evaluation. The aim of the Irish experiment was to determine the impact of different stocking rates (SRs) (SR1: 3.28 cow/ha, SR2: 2.51 cow/ha) on key physical, biological and economic performance. The aim of the French experiment was to evaluate over a prolonged time period, the ability of two breeds of dairy cows (Holstein and Normande) to produce and to reproduce under two feeding strategies (high level and low level) in the context of compact calving. The model evaluation was conducted at the herd level with separate evaluations for the primiparous and multiparous cows. The evaluation included the two extreme SRs for the Irish experiment, and an evaluation at the overall herd and individual animal level for the different breeds and feeding levels for the French data. The comparison of simulation and experimental data for all scenarios resulted in a relative prediction error, which was consistently <15% across experiments for weekly milk production and BCS. In relation to BCS, the highest root mean square error was 0.27 points of BCS, which arose for Holstein cows in the low feeding group in late lactation. The model responded in a realistic fashion to variation in genetic potential for milk production, herbage allowance and concentrate supplementation.
authors.affiliation: 1Teagasc,Animal and Grassland Research and Innovation Centre,Moorepark,Fermoy,Co. Cork,Ireland.
authors.forename: E
authors.initials: E
authors.lastname: Ruelle
authors.affiliation: 3INRA-Agrocampus-Ouest,UMR 1348, Physiologie, Environnement et Génétique pour l'Animal et les Systèmes d'Elevage,Domaine de la Prise,35590 Saint Gilles,France.
authors.forename: L
authors.initials: L
authors.lastname: Delaby
authors.affiliation: 4School of Agriculture, Food and Rural Development,Newcastle University,Newcastle upon Tyne,NE1 7RU,UK.
authors.forename: M
authors.initials: M
authors.lastname: Wallace
authors.affiliation: 1Teagasc,Animal and Grassland Research and Innovation Centre,Moorepark,Fermoy,Co. Cork,Ireland.
authors.forename: L
authors.initials: L
authors.lastname: Shalloo
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000822:Animal Husbandry; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001823:Body Composition; D002417:Cattle / Q000235:genetics / Q000502:physiology*; D003612:Dairying / Q000191:economics; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D005260:Female; D005602:France; D007494:Ireland; D007774:Lactation / Q000502:physiology*; D008892:Milk; D008954:Models, Biological; D010298:Parity; D011247:Pregnancy
keywords: body condition score; dairy cows; milk yield; model evaluation; modelling