Chemical composition and nitrogen availability for goats and sheep of some olive by-products

Abstract

By-products from olive culture and related industry may play an important role in goats and sheep feeding in the Mediterranean area. The assessment of their nutritive value is essential for an adequate use of those by-products. Olive cakes (OCs) from different oil extraction processes and different olive mills, olive skins (OSs), olive pulps (OPs) and olive leaves (OLs) dried at ambient temperature or at 60 °C have been analysed for their nutrient composition. The chemical composition of those by-products is affected by factors like oil extraction process, year and mill. OCs CP content was variable (6.62–9.88 g/100 g DM) and, essentially linked to the lignocellulosic fraction (ADFN, 47–70.6 g/100 g total N), in analysed samples (E2SOC-J 1996, 1997 and 1998). Variable NDF (23.1–73.0 g/100 g DM) and ADL contents have been found (12.2–37.0 g/100 g DM). Total extractable polyphenols (TEPs) were detected (0.28–3.06 g/100 g DM of TEP). The in vitro nitrogen digestibility of OC was low and highly variable (1.97–34.9%). The CP content was also low in OLs (6.31–10.9 g/100 g DM) with an important and variable proportion being attached to the lignocellulosic fraction (35.4–53.3 g/100 g TN). Low but not as variable values as for OC have been observed for in vitro N digestibility of OL (10.4–15.1%). Phenolic compounds were also variable in OLs (1.41–4.29 g/100 g DM of TEP). The N ruminal degradability of OC and OL has been determined in Granadina goats and Segureña wethers. For OL there were not interspecies differences. Intestinal digestibility of the ruminal-undegraded protein was determined in vitro after an incubation period of 16 h in the rumen of goats and wethers. The values ranged from 35.3 to 42.1% for OC and from 34.5 to 53.1 for OL depending on both, by-product and animal species. The dietary protein digestibility and the digestible nitrogen acid detergent soluble (100-ADFN) were also calculated and a low correlation was obtained between those values.