THE EFFECTS OF YEAST EXTRACT ON THE IN-VITRO DEGRADATION OF LOW-QUALITY ROUGHAGE, DIGESTIBILITY, RUMEN FERMENTATION, BLOOD CRITERIA, AND IMMUNITY STATUS OF BARKI SHEEP

Yeast extract (YE) was prepared from yeast product with a live yeast cell concentration of 2.44 × 1011 CFU/g. Tested grounded roughages, including rice straw (RS), corn cops (CC), corn stover (CS), and wheat straw (WS) were used in an in-vitro digestibility trial without yeast extract (YE0) or with two levels of yeast extract supplementation; 2 g YE /kg DM (YEL1) and 4 g YE /kg DM (YEL2). The in-vitro study revealed that RS supplemented with yeast extract at level of 4g/kg DM (YEL2) recorded the highest in-vitro dry matter, organic matter and crude protein digestibility (IVDMD, IVOMD, and IVCPD) values. In order to clarify the results of the in-vitro study, a digestibility trial was design on 15 Barki rams (five rams / group). Three rations were prepared with the same roughage: concentrate ratio of 30:70%. The 1st (RSR):70% concentrate feed mixture (CFM) + 30% RS (control negative). Ration 2 (YER): 70% CFM + 30% RS supplemented with 4 g YE/kg DM. Ration 3 (CHR): 70%CFM + 30% clover hay (control positive). Results of the in-vivo study indicated that YE tended to significantly (P<0.05) increase DM, CP, CF, EE, and NFE digestibility compared with the negative control group (RSR). However, the positive control group (CHR) recorded significantly (P˂0.05) higher digestion coefficient of DM and CF (65.76 and 60.16%). Differences between CHR and YER were insignificant for CP, EE, and NFE digestibility. Yeast extract led to a significant (P<0.05) improvement in TDN, DCP, and NB by about 5, 22, and 22.8%, respectively, compared to negative control. Yeast extract caused a significant increase (P<0.05) in volatile fatty acids (VFA) concentration compared to the negative control at two and four h. post feeding. Rumen concentration of NH3-N followed similar trend. Serum total protein and albumin were significantly (P<0.05) higher with YER than those for CHR and RSR. Yeast extract did not show any adverse effect on liver and kidney functions, hematological and immunity parameters. It can be concluded that yeast extract supplementation at level of 4g/kg DM effectively improved the nutritional value of low-quality roughages and positively affected animal performance.