Bloat in cattle grazing alfalfa cultivars selected for a low initial rate of digestion: A review

Abstract

The occurrence of frothy bloat limits the practice of alfalfa grazing in spite of the availability of strains bred specifically for pasture. Bloat is a chronic condition, endemic to cattle. Prophylactics and management techniques are available to reduce its incidence but they are expensive, difficult to administer, conflict with traditional grazing management regimens and do not eliminate bloat in all circumstances. A program to breed and evaluate a bloat-reduced strain of alfalfa was initiated in 1980 to overcome some of these limitations. A review of the results of grazing and feeding trials using alfalfas with low initial rates of digestion (LIRD) shows that this new strain reduces the incidence and severity of frothy bloat on pasture. Their effectiveness in controlling bloat was related to feeding or grazing management practices, the maturity of the plants and the season of use. Graziers may reduce the risk of occasional livestock losses from bloat by using LIRD cultivars, like AC Grazeland, or managing species/cultivar mixtures in ways that reduce the initial rate of digestion. Other bloat preventive strategies, including co-seeding with bloat-free legumes and using bloat-controlling prophylactics in combination with a LIRD alfalfa, are being investigated. Key words: Bloat, alfalfa, lucerne, legume, low initial rates of digestion, cattle, grazing