had shorter (P < 0.04) gestation lengths than recipients that received embryos in the cool

season (all calves: cool season 278.8 + 1.1 days vs. hot season 274.3 + 1.4 days; live

calves: cool season 278.5 + 1.1 days vs. hot season 274.4 + 1.4 days).

Calf Sex Ratio and Birth Weight

 The calf sex ratio was different (P < 0.002) than the expected 50:50 ratio. In

particular, there was a preponderance of male calves among all calves born (31/40 =

77.5%) as well as live calves only (28/37 = 75.7%). There were no effects of embryo

treatment, season of transfer, farm-season or gestation length on calf sex ratio (Table 4-

3). The proportion of male calves born following artificial insemination at Farm 2 was

50% for all calves (27/54) as well as all live calves (26/52). This was significantly lower

(P < 0.04) than the proportion of male calves born following embryo transfer at Farm 2

(all calves: 16/20 = 80% and live calves: 15/19 = 79.0%).

 Calf birth weight was recorded for 20 calves at Farm 2. There were no effects of

embryo treatment, season of transfer, or calf sex on calf birth weight (Table 4-3). Of the

20 calves, one was born dead. This calf was from the IGF-1 treatment group and

weighed 68.2 kg at birth. For the 19 calves born alive, there was also no effect of embryo

treatment, season of transfer, or calf sex on calf birth weight (Table 4-3). Calves born

following artificial insemination at Farm 2 had lower (P < 0.001) birth weights than for

calves born following embryo transfer. This was true for all calves (artificial

insemination 41.1 0.8 vs. embryo transfer 48.2 + 1.3 kg) as well as all live calves

(artificial insemination 41.2 0.8 vs. embryo transfer 47.1 + 1.3 kg).

 Discussion

 The objective of the present experiment was to determine whether culturing

embryos in the presence of IGF-1 would increase pregnancy and calving rates following