Utilization of low quality resources by small ruminants in Mediterranean agro-pastoral systems: the case of browse and aftermath cereal stubble

Browse and cereal stubble represent the two most important resources for grazing small ruminants in dry Mediterranean areas. The purpose of the present review is to provide updated information regarding their nutritional value. In a mixed Mediterranean environment, browse represents at least 40% of goat’s diet. Most browse species in the Mediterranean are rich in tanniferous phenolic substances. Polyethylene glycol (PEG) can bind tannins irreversibly over a wide range of pH and is efficient in alleviating the negative effects of tannins. Supplementing with PEG improves intake and digestibility in grazing goats and sheep and has the potential to be economically profitable. The chemical composition of wheat stubble is affected by the cultivar of wheat and climate, but not tillage management. The quality of stubble from early maturing is lower than from late maturing cultivars. Stubble contains more protein in years of lower rainfall. If grains escaped from the harvest combine (2% of grain yield) are included, digestibility of OM from different components ranges between 680% (grain) to 640% (stem). Also, the energy requirement of sheep grazing on stubble may be 70% higher than in shaded feedlot. Therefore, the body condition changes of sheep grazing on stubble exhibit a cyclic pattern consequent with temporal changes in nutritive quality. Because stubble grazing is concurrent with the onset of oestrous season, supplementation with grains from legume species-rich in degradable protein-is needed to prevent impairment of body condition. Supplementing browsing goats with PEG, and sheep grazing cereal stubble with moderate amounts of legume grain, may enable the use of these traditional resources in the frame of sustainable production systems.