318 EFFECT OF BREED AND FOLLICULAR STATUS ON RESPONSE TO SUPEROVULATION IN SOUTH AFRICAN GOATS

Abstract

This study evaluated the effect of breed and follicular status on quantity and quality of embryos recovered following superovulation in South African goats. Mature, nonlactating Boer (n = 10) and unimproved indigenous (n = 10) goats were used in this trial. Oestrous cycles of does were synchronised with controlled internal drug release (CIDR^®; Pfizer Animal Health, New York, NY, USA) dispensers inserted for 9 days and injected with prostaglandin at CIDR insertion. All does were superovulated with pFSH, administered in 7 dosages, at 12 h intervals, starting from 48 h before CIDR removal. Ultrasonographic scans were performed at initiation of the superovulation treatment. Does were cervically inseminated with fresh undiluted semen at 36 and 48 h following CIDR withdrawal. Embryos were surgically collected at Day 6 following AI. The total number of recovered structures (unfertilised ova and embryos) was evaluated microscopically for the stage of development and quality, using morphological criteria. The structures were classified as unfertilised ova (if there was no cleavage), degenerate embryos (embryos at 8-cell stage and earlier stage), or as transferable grade 1, 2, and 3 embryos (morphologically intact compacted morulae, early blastocysts, and expanded blastocysts). All data were analysed using the ANOVA procedures of SAS (SAS Institute Inc., Cary, NC, USA). The time from CIDR removal to onset of oestrus did not differ significantly between breeds. Breed had no effect on the total number of corpora lutea, structures (unfertilised ova and embryos), unfertilised ova, embryos, degenerated embryos, and transferable embryos. The total number of follicles at the onset of pFSH treatment was positively correlated with the number of structures (unfertilised ova plus embryos) recovered. Similarly, the total number of embryos recovered was positively correlated with the number of follicles 2 to 3 mm and 4 to 5 mm, and the total number of follicles. The number of follicles 4 to 5 mm and the total number of follicles at the onset of pFSH treatment were positively correlated with total number of the transferrable embryos at the beginning of a superovulation treatment. The total number of transferable embryos was negatively correlated with the presence of follicles with a diameter >6 mm at the beginning of the superovulation treatment. In conclusion, breed had no effect on response to superovulation. The total number of follicles and follicle diameters 2 to 3 mm and 4 to 5 mm were positively correlated with embryo yield. The presence of follicles >6 mm at the beginning of superovulation negatively affected the quality of embryos. The results of this study indicate that breed has no effect on response to superovulation. However, the number and size of follicles at the beginning of a superovulation treatment affect both embryo yield and quality.