Newcastle disease outbreak in pheasants in Great Britain in May 1996

respectively. The mean plasma progesterone concentrations in the cycles subsequent to inoculation are shown in Fig 2; the duration of these oestrous cycles varied from 19 to 22 days, hence the data for the last four days of each cycle have been based on the subsequent day of oestrus. There were 10 cycles for the infected heifers and seven cycles for controls. During the mid luteal phase of the subsequent cycles, progesterone concentrations were consistently lower in the infected heifers than in the controls; the differences