Assisted reproduction in Nile tilapia Oreochromis niloticus: Milt preservation, spawning induction and artificial fertilization.

Methods for milt collection and chilled preservation, hormone-induced spawning and artificial fertilization were studied in Nile tilapia Oreochromis niloticus. Milt samples were selected from 5 male brooders. Each milt sample was divided into 4 treatments; 3 treatments were centrifuge-washed with 0.85% normal saline solution (NSS), and then added with the extenders (1) freshwater fish saline (FFS) or (2) modified fish Ringers solution (MFS), or without an extender as (3) NSS (control), while the fourth treatment was the unwashed control. Milt samples treated with either extender at 4 °C presented a sufficient sperm motility score (≥ 3) and sperm viability (≥ 70%) for up to 20 h post-collection. For female brooders, gonadotropin-releasing hormone analog (GnRHa) was used to induce spawning. The highest number of females spawned and a pseudo-gonadosomatic index were observed in groups that received two GnRHa injections (15 and 30 μg kg−1, 8 h interval) with an oral administration of a dopamine antagonist (5 mg kg−1). Artificial fertilization was performed with fresh and 20 h chilled-storage milt. Mean fertilization rates for the fresh and chilled milt fertilized groups were 83.6 ± 7.2% and 42.3 ± 5.1%, respectively, with hatching rates of 67.5 ± 3.5% and 28.3 ± 6.8%, respectively. Nevertheless, the development of fish larvae from both groups was comparable. This study indicated that artificial fertilization using chilled milt and GnRHa-induced-spawn produced healthy tilapia fry. Thus, the procedures facilitate breeding programs of Nile tilapia in pair mating selection and distribution of genetic materials. • A practical technique was developed to provide competent quality of tilapia sperm preserved at 4 °C for up to 20 h. • Spawning synchronization was accomplished with 2 GnRHa injection with an oral administration of the dopamine antagonist. • The embryo obtained from artificial fertilization using chilled milt and induced spawn eggs showed typical development. • The reproductive technique demonstrated in this study did not cause injury to the broodfish. [ABSTRACT FROM AUTHOR]