INFLUENCE OF REPEATED RESTRAINT AND ISOLATION STRESS AND ELECTROLYTE ADMINISTRATION ON CARCASS QUALITY AND MUSCLE ELECTROLYTE CONTENT OF SHEEP

Crossbred lambs were assigned, within weight blocks, to one of four treatments applied in a 2 X 2 factorial design (n = 6 per treatment). Treatment main effects included no stress (NS) or three consecutive days of restraint and isolation stress (RIS) and treatment with either water (W) or electrolytes (E). The experimental design resulted in four treatments, namely NS-lambs given W, NS-lambs given E, RIS-lambs given W, and RIS-lambs given E. Stress treatment consisted of moving each lamb from its home stanchion to a separate location and isolation from visual and tactile contact with other lambs for 6 hours daily for 3 days before slaughter. All lambs received a 320 ml oral drench of either W or E on each day after the stress treatment. Stress treatment reduced (P < 0.05) semitendinosus (ST) muscle glycogen by 4.8-fold. At 24 h post mortem, muscle pH for semimembranosus (SM), biceps femoris (BF) and infraspinatus (IF) was higher (P < 0-05) in RIS-lambs that in NS-lambs. Hunter L*a*b* values, measured on muscle cross-section, revealed a lighter (P < 0.05) BF; more (P < 0-05) red BF, ST, and longissimus dorsi (LD); and more (P < 0.05) yellow ST, SM, BF, and LD for NS-than for RIS-lambs. Muscle from RIS-lambs contained less (P < 0.05) potassium than that from NS-lambs. Restraint and isolation stress of lambs resulted in a reduction in muscle glycogen, but only slight increases in ultimate pH and minimal influences on muscle color. Administration of electrolytes had no effect on lamb carcass quality.