Quantifying the hydration status of lambs in relation to carcass characteristics

Abstract

An experiment was undertaken to determine the physiological effects of water deprivation on lambs before slaughter. The aim of this experiment was to develop a method for quantifying the hydration status of lambs in relation to any subsequent effects on carcass and meat characters. Forty-eight crossbred lambs were subjected to 1 of 4 treatments: (i) normal ambient air temperature with access to water; (ii) normal ambient with no access to water; (iii) high ambient air temperature with access to water; and (iv) high ambient air temperature with no access to water. The treatments were imposed for a period of 48 h, after which the lambs were slaughtered. Food was withheld from all lambs during this 48 h period. Serum and urine were collected from each lamb at 0, 24 and 48 h and the concentrations of a range of analytes measured. Muscle, viscera and gastrointestinal tract were sampled immediately after slaughter. Water deprivation for a period of 48 h caused an increase in liveweight loss but no change in hot carcass weight or dressing percentage. Water deprivation caused an increase in muscle dry matter concentration and osmolality. The concentrations of protein, β-hydroxybutyrate, glucose, creatinine, potassium or albumin in serum were not affected by water deprivation. The concentration of sodium and chloride ions in serum and urine increased with feed deprivation time in lambs which had no access to water, but did not change for lambs that had access to water. Interactions occurred between water access and ambient air temperature for some but not all parameters. A significant relationship was found between muscle dry matter concentration, serum sodium concentration and urine specific gravity. It was concluded that urine specific gravity is a sensitive indicator of water consumption. Serum sodium concentration and urine specific gravity used together may be useful to predict the muscle hydration status of lambs.