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

In three experiments conducted over successive breeding seasonsʹwe 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. fects of treatment duration on oestrous synchrony, ovulation and fertility were investigated in Experiment 2. Each of 80 mature does had a device inserted for 20, 17, 14, 11, or 8 days and with PG 48 h after insertion. Device withdrawal occurred synchronously on 6 May. Does were inseminated by laparoscopy 70 h after device withdrawal. Oestrus was detected in 84% of does, but varied from more than 90% for treatments of 14–20 days to 81% and 50% with the intervals of 11 days and 8 days, respectively (P < 0.001). Conception rates, assessed by rectal ultrasonography 45 days after artificial insemination, varied from 44% (17 days) to 80% (14 days) (P = 0.10), with a significant interaction between the occurrence of oestrus and conception rate (P < 0.05) manifest as improved conception rates amongst oestrous does receiving the 8 day treatment. Plasma progesterone profiles indicated that all treated does ovulated, but some delayed responses with the shortest treatment interval were due to the presence of luteal tissue at device removal. fects of buck presence or absence on ovulation and fertility within the breeding season were investigated in Experiment 3. Does were allocated to one of three treatment groups (n = 30, n = 30 and n = 28) which were run continuously in the presence of a vasectomised buck, or isolated from bucks until 10 days after AI, or completely isolated from bucks throughout the study. All does were synchronised with a device inserted for 14 days and were inseminated laparoscopically as in Experiment 2. Differences in conception rate to AI, ranging from 43% (1330) to 68% (1928), were not significant. Analysis of plasma progesterone profiles indicated that all does ovulated following device withdrawal. studies have demonstrated marked effects of season and treatment duration on the efficacy of the CIDR device to synchronise oestrus and ovulation in fallow deer. Furthermore, it is concluded that buck presence is not a prerequisite for an ovulatory response.