Chemical composition and in vitro digestibility of alternative feed resources for ruminants in Mediterranean climates: olive cake and cactus cladodes

摘要

Olive cake (OC) and cactus cladodes (CCs) are two alternative feed resources widely available in Mediterranean areas. Their use in ruminant diets was assessed according to their chemical composition, secondary compound levels and digestibility. The effects of the olive oil extraction period and process, and CCs age and sampling period were evaluated. OC was collected monthly, from November to January, from mills using either a mechanical press or 2-phase or 3-phase centrifugation processes. CCs were collected fortnightly according to age (young and mature) from April to June. Two-phase OC had the lowest content of dry matter (DM), the highest nitrogen-free extract (NFE) and total and hydrolysable tannins and was more rapidly fermentable. Mechanical press OC was the least digestible. OC DM, protein and NFE were affected linearly by the extraction period. Gas production (GP), in vitro digestibility parameters and dry and organic enzymatic digestibility changed with the extraction period. Therefore, OC chemical composition and in vitro digestibility depended mainly on the extraction process and period. Compared to mature CCs , young CCs contained more water, protein, ether-extract and phenolic compounds, but less ash and fibre. GP and digestibility parameters were not affected by age, but in vitro organic matter digestibility and microbial biomass production were higher in young cladodes. CCs chemical composition, GP and digestibility parameters were influenced by the collection period. Due to its limited nutritional quality, OC should be enriched in nitrogen, while CCs could be considered as highly valuable forage in ruminant diet.