Frequent blood sampling changes the plasma concentration of LH and FSH and the ovulation rate in Merino ewes

During earlier studies we observed that ewes housed and sampled intensively to measure pulses of LH in plasma had a higher ovulation rate than similar ewes housed outside. In Expt 1, we pursued this observation by testing whether the increase was due to effects of housing or collection of blood samples. Ewes sampled at intervals of 4 h for 2 days before progestagen sponge removal and 2 days after sponge removal, and every 20 min for 12 h the day before sponge removal and every 10 min for 4 h on the day of sponge removal had a higher ovulation rate than ewes that were not sampled (1.72 versus 1.41; P<0.05)