Potential use of olive by-products in ruminant feeding: A review

This review presents recent knowledge on the inclusion of by-products from olive trees and olive oil extraction in the diets offered to goats and sheep. Olive by-products are evaluated with respect to their composition, digestion, degradation, ruminal fermentation, and their impact on animal performance and on product quality, with particular attention to their fatty acid profile. Olive leaves are fibrous with a low digestibility, especially of crude protein (CP), and they promote very poor rumen fermentation. However, if adequately supplemented, they may be successfully used in animal diets. The nutritive value of olive leaves is greater when fed fresh, although dry leaves may be incorporated in the diet. When olive leaves are rich in oil, ruminal protozoa decrease, and this could increase the efficiency of microbial protein synthesis in the rumen. It has also been observed that for lactating animals olive leaves result in an improvement in milk fat quality compared to diets based on conventional forages. However, more research is needed to assess the potential toxic effect of the high levels of copper in olive leaves. The use of olive cakes in ruminant diets promotes different responses in rumen fermentation, depending on the method of administration and the proportion in the diet. Both feeding as silage or incorporation into feed blocks have proved to be satisfactory. Extracted olive cake provides cheap energy and fibre to the animal and high-fat olive cake may be used to improve the quality of the fat in the animal products.