title: Fertilization and embryo loss in Booroola Merino x South Australian Merino ewes: Effect of the F gene.
abstract: The effects of Booroola genotype (F+, ++); the number of ovulations per ewe (one, two or three); and the age of a ewe (2.5 yr vs 3.5 to 6.5 yr) on the percentage of ova fertilized, embryo loss and fetal loss were examined in Booroola x South Australian Merino ewes slaughtered on Days 4, 21 and 90 after insemination. Ewes slaughtered on Day 90 were examined by real-time ultrasound imaging (RUI) on Day 45. Fertilization failure was independent of ewe genotype, ovulation rate and age of ewe, and it was not an important source of wastage (F+, 9.4%; ++, 6.7%). Most embryo loss occurred during the first 21 d (F+, 54.7%; ++, 40.3%). Interpretation of the effects of genotype and ovulation rate on embryo wastage measured on Days 21, 45 and 90 was obscured by significant (P < 0.05) genotype and ovulation rate interactions with the day of slaughter/RUI. The effect of age on embryo loss was not significant (P > 0.05). Reasons for the high rate of wastage observed in this experiment require further study.
authors.affiliation: Department of Agriculture, Turretfield Research Centre Rosedale, S.A. 5350, Australia.
authors.forename: D O
authors.initials: DO
authors.lastname: Kleemann
authors.forename: S K
authors.initials: SK
authors.lastname: Walker
authors.forename: J R
authors.initials: JR
authors.lastname: Walkley
authors.forename: D H
authors.initials: DH
authors.lastname: Smith
authors.forename: R J
authors.initials: RJ
authors.lastname: Grimson
authors.forename: R F
authors.initials: RF
authors.lastname: Seamark