Pregnancy Rate

 Using plasma progesterone concentrations greater than 2.0 ng/mL as a diagnosis

of pregnancy, the proportion of cows pregnant at day 21 after ovulation was not different

between recipients that received control versus IGF-1 treated embryos (Table 4-1).

However, there was a tendency for an increased proportion of recipients with plasma

progesterone above 2.0 ng/mL in the hot season (P < 0.06) compared to the cool season

(Table 4-1). There was also a trend for an interaction between season and treatment (P <

0.09) with a higher pregnancy rate for recipients receiving IGF-1 treated embryos than

recipients receiving control embryos during the hot season but not the cool season (Table

4-1).

 As shown in Table 4-1, there was a season x embryo treatment interaction that

affected pregnancy rate at day 30 and day 45 of gestation (P < 0.01). In the hot season,

recipients that received IGF-1 treated embryos had higher pregnancy rates at both day 30

and day 45 than recipients receiving control embryos. In the cool season, in contrast,

there was no difference between recipients receiving IGF-1 treated embryos or control

embryos.

 Farms 2 and 3 were the two locations where transfers were performed in both

seasons. When data from these two farms only were analyzed, there was an interaction

between season and IGF-1 (P < 0.01) for pregnancy rate at day 21 (cool season: control

- 27/35 = 77.1% and IGF-1 2134 = 61.8%; hot season: control 41/59 = 69.5% and

IGF-1 51/63 = 81.0%), day 30 of gestation (cool season: control 12/35 = 34.3% and

IGF-1 5/34 = 14.7%; hot season: control 15/71 = 21.1% and IGF-1 34/69 = 49.3%)

and day 45 of gestation (cool season: control 10/35 = 28.6% vs. IGF-1 6/37 = 16.2%;

hot season: control 13/71 = 18.3% vs. IGF-1 28/67 = 41.8%).