Embryo length on Day 15 was analyzed using a linear regression model with progesterone on Day 7 as the predictor variable (linear term) for each response. Analyses were conducted separately for each year and farm was treated as a fixed effect within year. In yr 1, analysis of the Day 15 embryo length data was conducted with farm 4 analyzed separately from farms 1 to 3. We had 4 farms in yr 1 (1, 2, 3, and 4) and 2 farms in yr 2 (1 and 4).