An in vitro evaluation of some unconventional ruminant feeds in terms of the organic matter digestibility, energy and microbial biomass.

In vitro organic matter apparent digestibility (IVOMAD), true digestibility (IVOMTD), metabolizable energy (ME), net energy lactation (NEL), microbial nitrogen (MN) and synthesis of microbial biomass (MBM) were estimated to predict the nutritive values of some agricultural by-products, drought-tolerant range plants and browses. The relationships between in vitro gas production (GP), and true or apparent digestibility. MN and MBM were studied utilizing an in vitro incubation technique. The values of IVOMAD, IVOMTD, ME, NEL, GP, MBM and MN varied with the studied experimental materials. The true fermentation of the outside part of Atriplex leucoclada produced a higher volume of gas than the middle or the inside parts, and this was associated with an increase in the values of IVOMAD, IVOMTD, ME and NEL. However, screening off the wood from olive cake to obtain olive cake pulp increased the IVOMAD, IVOMTD, ME, NEL and the volume of gas production from the true fermented material. One ml of gas was generated from the true degradation of 5 mg of wheat straw, Moringa oleifera, Alhagi camelorum, Eucaliptus camaldulensis and A. leucoclada, from 11 mg of Prosopsis stephaniana and olive cake pulp, and from 20 mg of olive cake or olive cake wood. The amount of MN or MBM produced from 100 mg of truly fermented organic matter depended on the kind of the fermented material and amounted to 0.7-2.9 mg or 8-34 mg, respectively. Crude fibre was negatively correlated to IVOMAD, IVOMTD, ME and NEL. Gas production was positively correlated to IVOMAD and IVOMTD but negatively correlated to MBM and MN.