Channel catfish (Ictalurus punctatus) production traits can be improved by gene editing and gene transfer, and these fish can be utilized without environmental risk by mutating reproductive genes associated with the hypothalamic-pituitary-gonadal (HPG) axis. Since these fish are sterile, fertility needs to be temporarily restored via normal hormone induced spawning to maintain a brood stock population and produce fry for production. A baseline control was normal channel catfish pairs induced to spawn with 100µg/kg female body weight (BW) luteinizing hormone releasing hormone analogue (LHRHa) implants, resulting in 55.0% spawning (N=20), a 69.7% hatching rate and 2883 fry/kg female BW produced. Channel catfish edited for various combinations of fsh, lh and mc4r were induced to spawn in bags or tanks with various combinations of 50 and 100 µg/kg LHRHa implants coupled with 1200, 1600 and 2000IU of human chorionic gonadotropin (HCG) or equine chorionic gonadotropin (ECG) delivered as a 20% priming and 80% resolving injection 12 hours apart in a series of comparisons.
Statistical analysis is ongoing but the trend indicates that ECG is no more or less effective than HCG for spawning of gene edited channel catfish. ECG appeared to produce less consistent results. Also, ECG appeared to need to be coupled with 100µg rather than 50 µg LHRHa to be effective (end point in some cases is eggs/kg rather than fry/kg because of excessive environmental effects during hatching). Although variable and in contrast to ECG, 100 µg of LHRHa appeared to reduce effectiveness of hormone induced spawning compared to 50 µg of LHRHa. If treatments are pooled by hormone, the baseline control (55.0%) and HCG (51.5%, N=99) had slightly higher spawning/ovulation % compared to ECG (42.8%, N=14). Another, drawback of ECG is that it is more expensive than HCG. Fry output appeared slightly higher for the control than for HCG treatments. A combination of LHRHa and HCG hormone induced spawning appears to be a feasible option to restore fertility for channel catfish sterilized by editing HPG axis related genes, but protocols need further optimization.