J. Anim. Prod. Adv., 2013, 3(2):40-48The objective of this study was to evaluate the effects of days in feedlot (DF) on physico-chemical properties and meat tenderness of Tanzanian long fat-tailed sheep (TLS) of Tanzania. Seventy castrated TLS (12 months old and mean live weight of 21.1 0.6 kg) were randomly assigned to seven treatment periods of DF in a completely random design experiment. The periods were 0, 14, 28, 42, 56, 70 and 84 days, designated as DF0, DF14, DF28, DF42, DF56, DF70 and DF84, respectively. Each treatment period had 10 experimental animals. Immediately after purchase, DF0 animals were slaughtered and their meat quality characteristics were determined. DF14, DF28, DF42, DF56, DF70 and DF84 groups were fed Cenchrus ciliaris hay as basal diet and molasses-based concentrate diet (160 g CP and 10.9 MJ ME/kgDM) and water on ad-libitum basis. At each period of stay, 10 experimental animals were randomly selected and slaughtered until the end of the feedlot period of 84-d was reached when the last group was slaughtered. Carcass pH and temperature were measured at 45 min, 6 h, 24 h and 48 h post mortem at the m. longissimus thoracis et lumborum (LL) muscle. The m. longissimus thoracis et lumborum (LL), semimembranosus (SM) and supraspinosus (SP) muscles were then dissected from the carcass and evaluated for drip loss (%), cooking loss (%) and Warner-Bratzler shear force (WBSF) values, after zero and nine days of aging. The results from this study revealed that there was a significant (P<0.001) decrease of pH values at 6 h post mortem (pH6) as the DF increased. The pH at 24 h post mortem (pH24) ranged from 5.72 to 5.79 and was not significantly (P>0.05) affected by period of stay. Cooking losses decreased (P<0.05) with increasing DF and aging duration from 0 to 9 days. The WBSF values of cooked muscles were highest (P<0.05) in SP followed by SM and lastly LL and their overall tenderness increased with increasing DF. There was an interaction effects between DF and post mortem aging time on tenderness such that castrates under DF56, DF70 and DF84 showed the lowest shear force values in LL and SMmuscles after nine days of aging. The results indicated that 42 days was optimal DF for production of high quality meat in Tanzanian long fat-tailed sheep.