ChileanJAR

A milk production simulation model was modified in relation to potential intake equation, substitution rate, second grazing pasture addition, different protein levels in the ration, economic indexes determination and ability of the model to analyze the systems under varying price conditions. These changes allowed the adequate prediction of different production systems with variations in the levels of forage, concentrate, calving dates and potential milk production. Different production systems were evaluated with this improved model; net income per cow, per hectare and margin per liter of milk produced increased as the level of alfalfa in the ration increased. The largest effect upon net income was achieved as the potential milk production increased from 5,000 to 6,500 liters/lactation. When the alfalfa ration was increased from 4 kg to 15 kg the profits increased from 11.1 to 17.6 $/liter for cows with potential productions of5,000 liters and from 23.8 to 30.9 $/liter for cows with potential productions of 6,000 liters/lactation, respectively. Net income for cows receiving 12 kg of alfalfa was 328 and 617 thousand Chilean $/ha for production potentials of 5,000 and 6,000 liters/lactation, respectively, whereas net income increased from 220 to 329 thousand Chilean $/ha when the levels of alfalfa varied between 4 and 15 kg, respectively, for cows producing 5,000 liters.