The effect of physiological parameters on serum lactate dehydrogenase isoenzymes in lambs.

The effect of age, sex and growth rate on total serum lactate dehydrogenase (LDH) and its isoenzymes was assessed in Suffolk X Halfbred lambs from 1.5 days to 10 weeks old. The total LDH activity was higher at 1.5 days than in older lambs and the percentage of LDH1 tended to increase while LDH4 and LDH5 decreased with age from 2 weeks, indicating that the isoenzyme distribution was changing towards the adult pattern. In female lambs, the percentage of LDH1 was higher than in male lambs at 1.5 days, but little importance was attached to this finding since the difference was not significant at 10 weeks. No clear relationships existed between the level of total LDH or its isoenzymes and daily liveweight gain. The age-related changes were considered to be of greater significance than those related to sex and growth rate when interpreting serum LDH levels in lambs.