Growth performance, blood composition, carcass characteristics, and meat quality of Ossimi and Barki fattening lambs as influenced by breed type and zilpaterol hydrochloride supplementation

To study the effect of zilpaterol hydrochloride (ZH), 60 lambs were divided into six groups of different breeds (Ossimi or Barki) receiving 0 [CON], 0.10 [Z1], or 0.15 [Z2] mg/kg BW. Ossimi had higher feed intake, carcass traits, blood hemoglobin, and neutrophils, but lower meat protein and blood basophils. Dietary ZH was associated with linear improvements in feed intake, feed conversion ratio, body weight, daily gain, meat protein, pH, tenderness, and water holding capacity, blood hemoglobin, hematocrit, red blood cells, neutrophils, glucose, total protein, insulin-like growth factor 1, triiodothyronine, and thyroxine levels. In contrast, dietary ZH was associated with linear decreases in meat fat and in plasma cholesterol and triglyceride levels. The weights of the kidney fat, supraspinatus muscle, flank, best rib, and best rib fat and bone proportions were quadratically influenced by dietary ZH. Breed by diet interactions were observed, with Z2 × Barki showing increased values for carcass weight, dressing percentage, liver, right side, left side, shoulder, round, ribs, and longissimus, supraspinatus, and semimembranosus muscles compared to CON. Conversely, Z2 × Ossimi exhibited decreased values for these traits. Notably, ZH treatment reduced kidney and omental fat in Barki, and increased these in Ossimi.