The present study was conducted to assess the inclusion of liquid protein feed (maize steep liquor; MSL) in growing lambs fed low-quality forage (400 g/kg wheat straw, dry mater basis) compared with two protein sources (soybean meal; SBM, and cottonseed meal; CSM). Eighteen male Farahani lambs, average body weight 36 ± 3.3 kg, were allocated to individual pens for 9 weeks. Three protein sources were: (1) MSL; (2) SBM and (3) CSM. Feed intakes did not differ among treatments. Growth rate and feed conversion ratio were improved in SBM-fed lambs. Nitrogen efficiency was improved in MSL v. CSM-fed lambs. Digestibility of fibre was enhanced in lambs fed SBM diet. Ruminal short chain fatty acid was highest in lambs fed SMB and lowest in lambs fed CSM. The urinary allantoin concentration was greater in SBM-fed lambs, with improved microbial crude protein synthesis. Blood urea nitrogen tended to be reduced in SBM-fed lambs. Dressing percentage improved in SBM-fed lambs. Lambs fed with SBM also grew faster and more efficiently than lambs fed either of the other two diets. However, regardless of the positive effects of SBM on the performance and ruminal fermentation profile observed in the current study, the MSL diet could be a profitable protein source in comparison to CSM in growing lambs fed low-quality forage. In conclusion, the present study indicates a positive outlook for feeding a liquid protein source to growing lambs fed low-quality forage such as wheat straw.

The effect of liquid protein feed (corn steep liquor; CSL contain CP, DM basis) and its comparison with conventional protein sources (i.e. soybean meal; SBM and cottonseed meal; CSM) were evaluated in fistulated sheep fed with high wheat straw level included in diet ( g/kg, DM basis). The study was carried out on three ruminal fistulated sheep in × Latin square design with -d periods (the first -d for adaptation period and the last -d for sample collection). The treatments were; ( ) CSL; ( ) SBM and ( ) CSM included in basal diet. Microbial protein synthesis, ruminal fermentation, nutrients digestibility, hematology and blood metabolites were evaluated in the current study. Results show that intake was not differed among treatments (P > . ). However, NDF digestibility was increased in SBM fed sheep (P = . ). Total short chain fatty acid production was . , . , and . mmol for CSL, SBM and CSM, respectively (P = . ). Purine derivate as well as microbial protein synthesis were increased in sheep fed SBM (P = . ). The hematology of sheep was similar among treatments. Among blood metabolites only blood urea nitrogen was tended to be lower in SBM diet. In conclusion, results show that CSL as liquid protein feed could include in sheep fed high wheat straw diet with no negative effect and further works need to improve its nitrogen efficiency in animal nutrition.