Modelo matemático para predecir la ingesta de materia seca de vacas lecheras de pastoreo

In a grazing system in dairy cows, there is a direct relationship between milk production and dry matter intake (DMI), hence the importance of measuring them, however, its hard work and high costs. The objective of this study is to design a mathematical model to predict the dry matter intake of dairy cows in a grazing system. This model based on the basic principle of fill-unit system. In this system, cows and feed are described in terms of feed intake capacity (FIC) and fill (units / amount of feed), respectively. The FIC determined by the animal's ability to process feed intake that depends on factors such as size, age and lactation status. The Fill determined by the properties of the feed such as digestibility, crude protein, among others. In the design of the model, an ad libitum feed assumed. Characteristics of the animal are considered as parity, state of lactation and gestation to obtain its capacity of ingestion; To determine the Satiety value (SV) of each forage; Festuca arundinacea and Lolium multiflorum are the forage s considered by the model, described by dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), in vitro digestible organic matter (dOM). The fixed parameters of the model were determined by applying polynomial regression to data from three experiments in lactating dairy cattle from Baja California Mexico. The model allows predicting dry matter intake, using as inputs, easily measured data and does not require the knowledge of milk yield (MY) or body weight (BW), so the model is consistent. The results of the model are satisfactory, since they are similar to those obtained experimentally because the dry matter intake, on average, is 21.68 kg / d in one group and in the other of 23.44 kg / d, and when applying the model we obtain an estimate of 22,826 kg / d for a cow with characteristics similar to those of the cows under study.Los resultados del modelo son satisfactorios, ya que son similares a los obtenidos experimentalmente debido a que la ingesta de materia seca, en promedio, es de 21.68 kg/d en un grupo y en el otro de 23.44 kg/d, y al aplicar el modelo se obtiene una estimación de 22.826 kg/d para una vaca con características semejantes a las de las vacas en estudio