Optimized Dairy Grazing Systems in the Northeast United States and New Zealand. I. Model Description and Evaluation

Abstract

Parallels exist in the recent developments of dairy systems in the Northeast United States and New Zealand because of greater use of pasture grazing and feed supplements, respectively. Lessons can be learned from each system. However, major differences exist between the regions in the patterns of pasture production, the costs of supplementary feed, and milk prices. These differences affect the optimum use of feed. In this paper, a linear programming model developed to determine optimum feeding strategies for dairy systems in each country is presented. The model optimizes grazing management (rotation lengths) and the conservation of pasture subject to constraints on their use. Other feed resources include N fertilizer, grain, corn silage, and alfalfa silage. All feeds are represented in energy terms. The substitution of pasture intake by grain and forage supplements is included, and cow performance can be optimized by choosing from 73 seasonal calving herds that vary in calving date, lactation length, and daily milk production. The model predicts that marginal responses to grain feeding are between 1.35 and 1.8 kg of milk/kg of grain dry matter supplement, well within the range of responses reported in the literature. Evaluation of the model against data from nine grazing system treatments in New Zealand and two in Pennsylvania showed that model predictions averaged +3% (New Zealand) and +0.04% (Northeast) of measured milk production. The model could be used with confidence to study systems in both the Northeast United States and New Zealand.

Evaluation of agri-environmental policies for reducing nitrate pollution from New Zealand dairy farms accounting for firm heterogeneity

“…N fertiliser responses and minimum, maximum, and residual pasture masses are taken from McCall et al (1999). Feed energy, substitution, and utilisation rates are taken from McCall et al (1999) and Dexcel (2008a).…”

“…Feed energy, substitution, and utilisation rates are taken from McCall et al (1999) and Dexcel (2008a). Average pasture production is taken from Dexcel (2008b).…”

Modelo de formulación de raciones al mínimo costo para ganado de carne basado en el sistema NRC 2000

“…En general en Uruguay el nivel de suplementación en ganado de carne suele ser bajo (Orcasberro, 1994), niveles elevados de suplementación suelen afectar negativamente el consumo y la digestibilidad del forraje ocasionando una sustitución de forraje por concentrado (Moore et al, 1999;Caton y Dhuyvetter, 1997;Dixon y Stockdale, 1999;Bargo et al, 2003). Existen modelos de PL que incorporan explícita-mente la tasa de sustitución de forraje por suplemento en la formulación de dietas (McCall et al, 1999;Soto y Reinoso, 2004). El NRC (2000) no menciona corrección alguna en el consumo de pastura por efecto de la interacción suplemento-pastura, quedaría implícito en la ecuación que estima el…”

Profitability of Nitrification Inhibitors for Abatement of Nitrate Leaching on a Representative Dairy Farm in the Waikato Region of New Zealand

“…The structure of the model is based on that of an optimisation model that was subject to peer review in [32]. b.…”

“…N fertiliser responses and minimum, maximum, and residual pasture masses are taken from [32]. Feed energy, substitution, and utilisation rates are taken from [22] and [33].…”