Importance of Mediterranean forest products as food resource of domestic herbivores: the case of oak acorn

Abstract

Many Mediterranean trees and shrubs constitute real fodder reserves for livestock and wildlife. Because of their resistance to heat and frequent harvesting, browse species are the major feed resources especially under harsh conditions. In the Mediterranean area, the fruits of oak (acorns) are used in extensive feeding of cattle, goat, sheep and pig. Proximate analyses have revealed the chemical composition of cork oak acorn to be similar to that of cereals (e.g. barley). Acorn is rich in starch (56.6-59.9% DM) but poor in protein (less than 10% DM) content. Another particularity of acorns is their high level of tannins (4-15.9% DM) that are found particularly in the hulls. In goats, voluntary intake of acorn containing concentrate ranged from 763-1,091 g DM/day without any signs of physiological problems. However, there were significant decrease in apparent digestibility coefficients for dry matter, organic matter and crude protein. N retention was positive in kids offered acorns and live weight gain reached 43 g/day. Inclusion of acorn in the diet of rabbit decreased the in vivo digestibility by 10.8%, 11.5% and 17.5%, respectively, for DM, organic matter and crude protein, but no significant effect was observed on average daily gain, carcass yield and feed conversion ratio. These results suggest that acorns could replace partially conventional feedstuffs as either forages or concentrate feeds without affecting livestock performance but should reduce the feeding cost.