Alfalfa grazing systems in Argentina

Abstract

Relative to confined systems, direct grazing has some advantages, particularly lower operational costs, better use of alfalfa quality compared hay or silage, and healthier animal products for human consumption compared to feed-lots (lower total cholesterol content, less intramuscular fat content, and higher unsaturated fatty acids omega-3/omega-6 relationship). However, there are some disadvantages: risk of bloat, longer fattening period, and lower milk production on an individual cow basis. Correct alfalfa grazing management that complements high animal production with high levels of pasture yield and persistence, must be based upon the growing pattern of the plant in which new stems arise in series that come from axillary as well as crown buds, keeping a balance between active and dormant buds. From the grazing viewpoint, alfalfa has two important features: i) it can reach high values of leaf area index (LAI) without losing photosynthetic capacity in the lower leaves; and ii) speed regrowth after grazing depends primarily on reserve carbohydrate and protein content on crown and root rather than on remnant leaves. Based on the previous remarks, the best way to use alfalfa is under rotational grazing in which the main objective must be to combine adequate levels of grazing intensity with appropriate resting time. Alfalfa can tolerate intensive grazing periods as long as they are not frequent. Repeated interruption of the reserves cycle leads to loss of stand and the subsequent decrease in animal production.