REGULAR ARTICLE Effect of feeding olive-pulp ensiled with additives on feedlot performance and carcass attributes of fat-tailed lambs Mohammad Reza Taheri & Mohammad Javad Zamiri & Ebrahim Rowghani & Amir Akhlaghi Accepted: 9 July 2012 # Springer Science+Business Media B.V. 2012 Abstract Feed cost has a significant effect on the economic efficiency of feedlot lambs; therefore, the use of low-cost non- conventional feedstuffs, such as olive pulp (OP), has the potential to decrease the production costs. Because optimum inclusion of OP-treated silages has not been determined in feedlot lambs, an experiment was conducted to determine the effect of inclusion of OP ensiled with additives in the diet on the feedlot performance and carcass attributes of feedlot lambs. Ram lambs of Mehraban and Ghezel breeds (n 0 50 lambs per breed) were randomly allotted to 10 groups and fed with one of the nine diets containing OP silage or a control diet. Silage treatments were: (1) OP silage without additives (OPS), (2) OP ensiled with 8 % beet molasses and 0.4 % formic acid (OP-MF), and (3) OP ensiled with 8 % beet molasses, 0.4 % formic acid and 0.5 % urea (OP-MFU). The control diet contained 50 % alfalfa hay and 50 % barley grain. Three levels from each silage were chosen to replace the barley grain (10, 20, or 30 % dry matter basis). The lambs were slaughtered after 92 days, and the average daily gain (ADG), feed conversion ratio (FCR), and carcass character- istics were determined. Feeding OPS to fat-tailed lambs, at an inclusion level of 30 %, decreased the carcass dressing per- centage, mainly as a result of decreased brisket percentage, but the ADG and FCR values were not adversely affected. Ghezel lambs had higher ADG than Mehraban lambs, but the visceral fat weight percentage, flap weight percentage, and back fat depth were higher in Mehraban. The crude protein content in the longissimus dorsi (LD) muscle was higher in Ghezel, but the dry matter percentage was higher in Mehraban (P <0.05). Other attributes were not significantly affected by breed (P > 0.05). Most carcass characteristics, including major cuts, were not affected by OPS feeding; therefore, feeding OPS (up to 30 %) can be economical for feedlot lambs. Most carcass characteristics, including major cuts, were not affected by OPS levels used in this experiment; therefore, inclusion of OPS (up to 30 %) in the diet may reduce the cost of raising feedlot lambs. This also could help alleviate the problem of storage of OP in oil factories. Keywords Additives . Carcass . Lamb . Olive-pulp silage . Feedlot performance Introduction Olive by-products can potentially be fed to ruminants (Sansoucy 1985; Molina-Alcaide and Yanez-Ruiz 2008; Awawdeh 2011); but their low digestibility and high polyphenol contents, which decrease protein availability and microbial protein synthesis (Makkar 2003; Martin Garcia et al. 2003; Al-Masri 2005), might limit high inclusion levels in the diet or feeding for extended periods. Preservation of olive by-products as silage and use of silage additives are likely to increase their consumption by improving their nutritive value. Various approaches have been used to improve the nutritive value of olive by-products, includ- ing the addition of sodium hydroxide (Molina and Aguilera 1988) and urea (Al Jassim et al. 1997). The effect of olive by- products on meat quality was reported by Molina-Alcaide and Yanez-Ruiz (2008). On the other hand, inconclusive observations make it difficult to determine the appropriate inclusion level and feedlot responses to processing methods or feeding periods (Giozelgiannis et al. 1978; Al Jassim et al. 1997; Martin Garcia et al. 2003; Weinberg et al. 2008; Awawdeh 2011). Ebrahim Rowghani has already retired. M. R. Taheri : M. J. Zamiri (*) : E. Rowghani : A. Akhlaghi Department of Animal Science, College of Agriculture, Shiraz University, Shiraz, Iran email: mjzamiri@gmail.com M. J. Zamiri e-mail: zamiri@shirazu.ac.ir Trop Anim Health Prod DOI 10.1007/s11250-012-0224-z