The overall occurrence of estrus was 57.4% (417/726). There was no interaction between the occurrence of estrus and GnRH treatment (P0.21) and no effect (P 0.19) of farm location on P/AI. The P/AI was greater (P 0.0001) in cows that displayed estrus (61.9%; 258/417) than those that did not display estrus (41.4%; 128/309). However, P/AI was unaffected by GnRH treatment (P0.55;Fig. 2).