Effects of a Gonadotropin‐Releasing Hormone IIa 5/20‐μg/kg Dose versus a 20/80‐μg/kg Dose on Channel Catfish Ovulation

Abstract

AbstractThe production of (male Blue Catfish Ictalurus furcatus × female Channel Catfish Ictalurus punctatus) F1 hybrids by U.S. catfish farmers has increased dramatically during the last 15 years. However, hybrid catfish production requires hormone‐induced ovulation of female Channel Catfish and remains an inefficient process. Previously, we demonstrated that GnRH IIa given as a two‐dose injection (priming/induction) of 20/80 μg/kg of female body weight resulted in superior ovulation rates for Channel Catfish compared with salmon GnRH IIIa and mammalian LHRHa, which are products that are currently used at commercial catfish hatcheries. The objective of the current study was to determine whether GnRH IIa given at a quarter dose (5/20 μg/kg) would achieve results similar to those that were obtained with the full dose (20/80 μg/kg) and whether the response varied over the spawning season. Trials were conducted at three timepoints during the 2017 spawning season: early (May 1), middle (May 15), or late (June 5). At each timepoint, 20 females received an intraperitoneal injection with a full dose of GnRH IIa and 20 females received an injection with a quarter dose of GnRH IIa. Data were collected for female weight, latency, incidence of ovulation, and stripped eggs weight (g) per kilogram of female body weight. The data indicated that the quarter dose of GnRH IIa (5/20 μg/kg of female body weight) achieved results that were similar to those that were obtained with the full dose of 20/80 μg/kg.