Ruminal dry matter and nutrient degradability of different olive cake by-products after incubation in the rumen using nylon bag technique

Abstract

The experiment was conducted to evaluate the ruminal dry matter, crude protein and neutral detergent fiber degradability of different olive cake by-products including crude, exhausted, partly-destoned and partly-destined-exhausted olive cake using nylon bag technique. Chemical composition of different types of olive cake was significantly different. Crude olive cake had a low crude protein, high crude fiber, neutral and acid detergent fiber and relatively high fat content. Destoning and exhausting significantly increased crude protein content of olive cake; the latter decreased fat content and relatively increased its other contents. In addition, partial destoning lowered its crude fiber, neutral and acid detergent fiber. About 3 g of dry matter (DM) equivalent of samples were weighed in sealed nylon bags (6 cm × 7.5 cm, polyamide, 26% porosity, 40 ± 10 μ pore size), and incubated in the rumen of two cannulated Zel ewes (approximately 1 yr old, BW = 32.2 kg) that fed alfalfa hay and ground barely in a ratio of about 75:25 (DM basis) at 0, 3, 6, 12, 18, 24, 36, 48, 72 and 96 h. The DM degradation showed significant differences in soluble for soluble fraction (7.83, 8.85, 11.05 & 14.40%), slowly digestible fraction (24.33, 25.45, 29.80 & 31.45%), potentially degradable fraction (32.16, 34.30, 40.85 & 45.85%), fractional rate of disappearance (2.8, 3.0, 4.1 & 4.2% h) and effective degradability in crude, exhausted, partly-destined and partly destoned exhausted olive cake, respectively. The protein in different olive byproducts had the lowest degradable fraction and rate; however, the NDF and crude protein had similar trend to DM. The results revealed that low degradable fraction of DM, crude protein and neutral detergent fiber of olive byproducts are the most important limiting factors in ruminant nutrition.