LAUSR

Bovine twin birth is associated with detriments including increased embryo/fetal losses, malpresentation and dystocia. Incidence of these is lessened in bilateral versus unilateral twin pregnancy. This study was undertaken to assess use of follicular ablation by aspiration to create bilateral twin pregnancies in females with genetic potential for ~3.5 ovulations per cycle (Trio allele carriers). In Experiment 1, carriers (n = 30) and non-carriers (n = 10) were synchronized for ovulation and timed artificial insemination (TAI). Follicles (> 5 mm) in excess of one per ovary were aspirated ~16h preceding TAI. Follicle count for females with follicles on only one ovary was reduced to two. Blood was sampled 2 weeks post-TAI to assess progesterone (P4) concentrations; fetal count was determined by ultrasound 6 weeks post-TAI. P4 concentration post-TAI was significantly (P < 0.001) associated with both genotype and subsequent pregnancy status (pregnant non-carriers, 7.06 ± 0.68 ng/mL; pregnant carriers, 5.54 ± 0.55 ng/mL; non-pregnant non-carriers, 5.22 ± 1.05 ng/mL; non-pregnant carriers, 3.13 ± 0.42 ng/mL). Experiment 2 was undertaken to offset negative effects of follicular aspiration on subsequent P4 concentration observed in Experiment 1. Carriers (n = 38) and non-carriers (n = 32) were submitted to fixed-TAI and follicle ablation as described. Additionally, accessory corpora lutea were induced by administration of hCG (carriers) at d6 post-TAI. Consequently, P4 concentration post-TAI was significantly (P < 0.05) associated with subsequent pregnancy status (pregnant, 8.48 ± 0.61 ng/mL; non-pregnant, 6.70 ± 0.63 ng/mL) but not with genotype (carrier, 8.01 ± 0.59 ng/mL; non-carrier, 7.17 ± 0.64 ng/mL). Fetus number was greater in carriers (Exp1, 1.64 ± 0.81; Exp2, 1.45 ± 0.09) versus non-carriers (1.00 ± 0.00, both Experiments). Singles, twins, and triplets occurred in carriers in Experiment 1, whereas multiples in Experiment 2 were limited to twins. Genotype effects on pregnancy rate were not significant (P > 0.10) in either experiment. Results suggest follicular ablation to create bilateral twin pregnancies in Trio carriers is feasible but requires induction of accessory corpora lutea to offset the negative effects of follicular aspiration on subsequent P4 concentration.