and estrus status (standing to be mounted) was recorded. A
cow was determined to be in estrus if it was visually
observed to stand for mounting or if it had an activated
(color change from white to red), lost (with mount marks),
or partially activated Kamar. The timing of CIDR insertion,
CIDR withdrawal, interval to the second PGF2a injection,
and TAI was recorded for each animal. A schematic representation
of the synchronization protocol is shown in
Figure 1.
One week later, intact Angus bulls were placed with
cows (approximately 1:40 to 1:50), across treatments, for
the remainder of the 60- to 70-day breeding season. Cows
were examined for pregnancy status at 55 to 70 days after
fixed TAI by ultrasonography (Aloka-500; Sysmed Lab,
Chicago, IL, USA) to identify the time of conception.
A partial farm budget-type analysis for projected economic
outcome was calculated based on mean AI pregnancy
rate difference in each location and with the
following assumptions.