Effects of Replacing Concentrate Feed with Carob (Ceratonia siliqua) Pods on Growth Performance, Carcass Characteristics, Meat Quality, and Rumen Fermentation in Assaf Lambs

This study examined the effects of replacing 25% (P25) or 50% (P50) of concentrate dry matter (DM) with sun-dried carob (Ceratonia siliqua L.) pods on growth performance, apparent nutrient digestibility, carcass traits, meat quality, serum biochemistry, and rumen microbiology in growing Assaf lambs. Twenty-four weaned male Assaf lambs (initial body weight [BW] 27.0 ± 0.5 kg; 2.5 months of age) were randomly assigned to three dietary treatments (n = 8 per group) in a completely randomized design and fed for 16 weeks. P50 achieved the highest ANCOVA-adjusted least squares mean final BW (53.0 kg) and average daily gain (ADG) (220.8 g/d), followed by P25 (51.1 kg; 203.3 g/d) and the control (46.2 kg; 160.2 g/d) (p < 0.001). Feed conversion ratio (FCR) improved from 8.99 in the control to 6.16 and 6.11 in P25 and P50, respectively, with no significant difference between the two carob-supplemented groups (p < 0.001). Apparent DM and organic matter (OM) digestibility increased with carob inclusion at both 3 and 6 months of age (p ≤ 0.0001). Cold carcass weight (CCW) was higher in carob-supplemented lambs (p < 0.001), whereas carcass muscle proportion did not differ among treatments (p = 0.688), and carcass fat proportion was higher in P25 than in the control (p = 0.039). Warner–Bratzler shear force declined progressively with carob inclusion (p < 0.001), indicating improved meat tenderness. Serum total protein was highest in P25, whereas blood urea nitrogen (BUN), low-density lipoprotein (LDL), and glutamate oxaloacetate transaminase (GOT) decreased with carob inclusion (p < 0.001). Rumen pH was highest in P25 (6.40), total bacterial and lactic acid bacteria (LAB) counts increased, and protozoa counts declined (p < 0.001). Because carob pods replaced concentrate, rather than being added to an isonitrogenous diet, the combined effects of pods per se, reduced crude protein supply, and altered energy density must all be considered when interpreting the results. These findings support carob pods as a practical, locally available partial substitute for concentrate feed in Assaf lamb production under Mediterranean and Near Eastern conditions.