5.08 - Fixed time AI protocols for heifers

Figure 1: Treatment schedules for heifers in the multi-state controlled internal drug release (CIDR) trial (Lamb et al., 2006).

Figure 2: Oestrus synchronisation schedules involving use of the CIDR Select protocol in breeding programs for beef heifers that require heat detection or fixed-time AI.

Table 1: Oestrus detection – time of day when cows exhibit standing estrus
Time of day Cows exhibiting standing oestrus
6am to 12pm 26.0%
12pm to 6pm 18.1%
6pm to 12am 26.9%
12am to 6am 29.0%
Source: Adapted from Hurnik and King (1987); Xu et al. (1998), Perry, GA (unpublished data).


Table 2: Time course of early bovine embryo development
Event Day
Oestrus 0
Ovulation 1
Fertilisation 1
First cell division 2
8-cell stage 3
Migration to uterus 5–6
Blastocyst 7–8
Hatching 9–11
Maternal recognition of pregnancy 15–17
Attachment to uterus 19
Adhesion to uterus 21–22
Placentation 25
Definitive attachment of embryo to uterus 42
Birth 285
Source: Adapted from Shea, 1981, Flechon and Renard, 1978, Peters, 1996, Telford et al., 1990.
Source: Applied Reproductive Strategies in Beef Cattle (ARSBC) Proceedings