Effects of treatment on the binary outcome of conception to AI were analyzed using generalized linear mixed logistic models, with herd fitted as a random effect to control for clustering of the outcome within herds. Separate analyses were performed for first and second study insemination. Analyses were restricted to inseminations of cows calved during the spring calving period in 2012; inseminations of cows during the previous autumn calving period in 2012 were excluded.