The aim of this study was to evaluate the effect of Lactobacillus acidophilus (LAC), exogenous enzymes of ZAD® (exogenous enzyme preparation) or their combination on feed conversion, and dressing of rabbits fed different treatments of sugarcane bagasse (SCB). Five rations were allotted randomly to five groups of New-Zealand White (NZW) rabbits (n=10) with initial live body weight of (838±42.4) g and 5 weeks of age. Rabbits were fed on diets with different sources of fiber as follows, (i) a control diet composed of 100% berseem hay and 0% SCB, (ii) 50% berseem hay and 50% untreated SCB (USCB), (iii) 50% berseem hay and 50% SCB treated with L. acidophilus (LAC), (iv) 50% berseem hay and 50% SCB treated with ZAD® (ZAD), and (v) 50% berseem hay and 50% SCB treated with a combination of LAC+ZAD® (LZ). Treatments of SCB with L. acidophilus, ZAD® and LAC+ZAD® had the highest feed conversion ratio than both USCB and control. The dressing percentage of rabbits that fed the LAC and LZ diets was higher (P<0.05) compared with that in the other groups. Performance index (PI) for LAC group was improved (P<0.05) compared to that for the other groups; however, PI for USCB group was the lowest (P<0.05). It could be concluded that treating SCB with L. acidophilus, exogenous enzymes of ZAD® or their combination improved feed conversion and performance with more positive effects with L. acidophilus than the other treatments.

As a result of agriculture practices, million tons of agriculture are produced as a secondary or by-products; however, with low nutritive values. Many methods are applied to improve the nutritive value and increase its utilization in ruminant’s nutrition. The biological treatments are the most common with more safe-treated products. In most cases, the biological treatments are paralleled with decreased crude fiber and fiber fractions content with increased crude protein content. Direct-fed microbial and exogenous enzymes to animal are other ways of biological methods for improving nutritive value of feeds. Here in this review, we will try to cover the biological treatments of by-products from different sides view with different types of animals and different animal end-products.