Oestrous synchronisation in farmed fallow deer (Dama dama): effects of season, treatment duration and the male on the efficacy of the intravaginal CIDR device

Abstract

In three experiments conducted over successive breeding seasons'we aimed to determine the effects of season, treatment duration and the male on the incidence of oestrus, oestrous synchrony, ovulation and fertility in farmed fallow deer following treatment with an intravaginal progesterone device (CIDR-G). Stage of breeding season was studied in Experiment 1. Synchronisation involved device insertion for 14 days, with injections of prostaglandin analogue (PG) at insertion and 10 days later. Eighty mature does were divided into four equal groups that each received at least two repeated synchronisation treatments over a 9 week period. Treatment initiation was staggered between successive groups by 7 day intervals from March to May to span the rut. Untreated control does (n = 42) were mated to a crayon-harnessed buck to define the rut. Oestrus was recorded on 69% of occasions and ovulation on 80% among the treated does after device withdrawal. Oestrus was followed by ovulation on 98% of occasions. Silent ovulations occurred most frequently early in the breeding season. An oestrous response was absent initially but increased to 89–100% after the onset of natural rutting. Mean intervals to oestrous onset decreased, and oestrous synchrony improved progressively during the study, reflecting a pronounced seasonal effect.