The Effects of Substituting Dietary Soybean Meal with Maize Grain on Milk Production in Dairy Goats

摘要

Today the environmental sustainability of livestock has become increasingly important. Nitrogen excretion from livestock can lead to air and groundwater pollution, causing acid rain, fine air particulates, and greenhouse gas emissions that lead to climate change, groundwater nitrate poisoning, and surface water eutrophication. Often, livestock are fed diets with a protein content that is much higher than what they require. In this experiment, a herd of dairy goats of the Alpine breed, reared on a farm in the hills near Genoa, Italy, was used to study the impacts of being fed a low- or a high-protein diet. The high-protein diet did not improve milk yield and quality; on the contrary, it lowered the efficiency of dietary-nitrogen utilization, increased feeding cost, and, above all, increased nitrogen excretion and the associated environmental risks. In conclusion, a high-protein diet is not advisable, both economically and environmentally, and a precision feeding approach (i.e., supplying the nutrients required for a given body mass and level of production, and no more) is highly recommended.