A total of 375 cows were synchronized for either TAI or
TET using modified presynch-Ovsynch protocols. At Farm 1,
cows were presynchronized with two treatments of PGF
(25 mg, im) given 14 days apart on Day 38 and Day 24
(Day 0 ¼ day of expected ovulation). Cows received 100 mg
of GnRH (im) on Day 10 and 25 mg PGF im on Day 3. A
second treatment of GnRH was administered on Day 0,
72 hours after PGF administration. Cows at Farms 2 and 3
were presynchronized with two treatments of PGF as
described for Farm 1, except that the treatments occurred
on Days 36 and 22, respectively. As for Farm 1, cows
received 100 mg of GnRH on Day 10 followed by 25 mg
PGF on Day 3. A second treatment of GnRH was administered
on Day 1, 56 hours after PGF administration. For all
farms, Day 0 was defined as the presumptive day of
ovulation. For cows at Farm 1, Day 0 occurred between
68 and 74 days in milk. For cows at Farms 2 and 3, Day
0 occurred between 76 and 82 days in milk.