A review of published leptin data for growing lambs, older ewes and mature dairy cows in late lactation showed that only 0.30-0.37 of the variation in blood leptin concentration was explained by differences in body fat variably expressed as % of liveweight (LW), backfat thickness and body condition score (BCS) respectively (Wylie et al., 2002). In dairy cows between 15d and 226d postpartum, Wylie et al (2002) observed no overall correlation between leptin at slaughter and lipid expressed as % of LW, empty body weight or carcase weight and only a weak correlation in cows in mid-lactation. Losses of fat during early lactation may ‘uncouple’ the link between leptin and fat and produce a bias across all of lactation. Another explanation is that leptin may be more closely linked with lipogenesis than with the amount of stored fat. This study revisits some metabolite and hormone data from a previous investigation of IGF-1 changes in fed, fasted and re-fed sheep in the light of more recently obtained leptin concentrations in the same animals.