Ovulation, recovery and viability of ova collected surgically and nonsurgically as affected by PMSG/PGF₂[alpha] treatments

Abstract

Two hundred five heifers were utilized to examine factors affecting ovulation, recovery and viability of ova collected surgically and nonsurgically following PMSG/PGF2a treatments. Twenty-four crossbred heifers were divided into four groups of six animals each. Groups 1, 2, 3 and 4 received 0, 450, 900 and 1800 IU PMSG IM, respectively, on day 11 postestrus followed 48 hr later with 30 mg PGF2a. Treatments were repeated at 5-week intervals for a total of four stimulations. Mean ovulations for Groups 1, 2, 3 and 4 were 1,0 1.6, 2.4 and 12.4, respectively. Mean ovulation rate decreased in all groups between the third and fourth stimulations with a significant decrease (P, .05) in Group 4. Four hundred fourty-nine ova were surgically collected from 57 heifers. The number of ova recovered and percent viable were 87/72.4%, 295/67.1% and 67/64.2% for animals with 1 to 10, 11 to 20 and > 20 corpora lutea, respectively. Left and right ovaries accounted for 48.9% and 51.1% of corpora lutea and 51.7% and 48.3% of ova recovered, respectively. The percent of total ova surgically recovered, transferred and subsequently resulting in pregnancies were 60.4%, 67.8% and 55.3%, respectively. In comparison, 38 ova were nonsurgically collected in 11 attempts resulting in 67.9%, 65.8% and 56.0% of ova recovered, transferred and pregnant, respectively.