The plasma PRL and GH concentrations in ewes exposed en to increasing photoperiod during the early post partum 7/7period are shown in Fig. 1A and B. At the onset of the experiment, the mean plasma PRL concentrations in both the LDC and LDM groups were similar(193.2 t 10.9 and 192.3 t 8.7 ng/ml, respectively). During the subsequent collection(second), the mean PRL concentration in the LDC group was 166.2 8.0 ng/ml.