Ovaplant®; Salmon Gonadotropin – Releasing Hormone Analogue (sGnRHa)
Method of Administration
Required INAD Fee
Drug History and Summary
The use of hormones to induce spawning in fish is critical to the success of many federal, state, private, and tribal fisheries programs. A wide variety of programs, including many that involve the restoration of threatened/endangered species, are dependent upon hormone treatment to complete final gamete maturation and ensure successful spawning.
The time of spawning is by its own nature a stressful period for all fish species. Both sexes are undergoing significant changes in physiology, morphology, and behavior. The additional handling of fish required during the spawning process complicates an already delicate situation. This is particularly true for wildstock species that must endure the added stresses of capture, handling, and confinement in an un-natural environment. In fact, with respect to some wildstock species, the stress of capture alone is often sufficient to cause complete reproductive failure unless spawning is induced by a spawning aid. Hormone treatment in a variety of fish species is essential to facilitate optimal spawning success.
Studies have shown that final gamete maturation (ovulation and spermiation) in fish can be induced by the administration of a variety of hormones (Donaldson and Hunter 1983; Goetz 1983). Investigations have found that synthetic analogues of gonadotropin releasing hormones (GnRHa) to be one of the more effective means of inducing final gamete maturation. These compounds, which may be similar to native gonadotropins found in either fish or mammals, are preferred choices as they typically exhibit both high biological activity and low species specificity. Although a number of these analogues are available, the most commonly used analogue for fish culture to date has been luteinizing hormone releasing hormone (LHRHa; Alvarino et al. 1992; Donaldson et al. 1981; Erdahl and McClain 1987; Fitzpatrick et al. 1984; Taranger et al. 1992; and Van der Kraak et al. 1983). Effective treatment has been reported using both injection and pellet implant therapy.
The use of implants that contain GnRH analogues has been evaluated over an extended period of time (Crim et al., 1983a). In early attempts to use implants, the peptide was imbedded in cholesterol pellets that contained cellulose to affect release rate (Sherwood et al., 1988). In this system, a 5% carboxymethyl cellulose / 95% cholesterol pellet containing mammalian GnRHa (mGnRHa) released an initial burst of mGnRHa followed by a sustained release of peptide over the next 28 days. Several researchers have demonstrated that these types of implants were capable of inducing maturation in a variety of species including: Atlantic salmon (Crim et al., 1983a; Crim and Glebe, 1984), herring (Carolsfeld et al., 1988), sea bass (Almendras et al., 1988), rainbow trout (Crim et al., 1983b; Crim et al., 1988) and milkfish (Lee et al., 1986; Marte et al., 1988). In all of these studies, mGnRHa was the imbedded peptide that induced maturation either in advance of, or synchronously within, a population.
The inclusion of salmon GnRHa (sGnRHa) instead of mGnRHa in Ovaplant® implants designed for inducing maturation in cultured fish is a logical one. In both in vitro (pituitary fragments or cell cultures) and in vivo studies, sGnRHa has been found to be more potent in effect than mGnRHa for many species including: goldfish (Peter et al., 1985, 1987), Atlantic salmon (Crim et al., 1988), rainbow trout (Crim et al., 1988; Weil et al., 1992), winter flounder (Crim et al., 1988) and catfish (Namvongchong et al., 1992b; Schulz et al., 1994). This potency may be attributed to high pituitary binding affinity and gonadotropin hormone (GtH) releasing capacity, even though sGnRH itself may not be an indigenous form for some of the species tested (Schulz et al., 1993). Moreover, sGnRHa produces a sustained level of GtH from pituitary cells with a low effective dose (Peter et al., 1987). Additionally, sGnRHa either as peptide alone or as Ovaprim® (sGnRH + a domperidone, Syndel International, Inc.) has proven to be effective in inducing final gamete maturation in a variety of cultured fish including, but not limited to, chinook salmon (Powell, 1995), coho salmon (Powell et al., 1998), catfish (Namvongchong et al., 1992b; Schulz et al., 1993), and ricefield eel (Tao and Lin, 1993). Furthermore, sGnRHa is an attractive spawning aid for use in fisheries and aquaculture because it has been shown to be ineffective in mammals (Millar et al., 1993), and has a short half-life in fish (Goren et al., 1990; Zohar et al., 1990; Weil et al., 1992). Conversely, mGnRHa is superactive in humans and has a prolonged half-life in fish and water (Sherwood and Harvey, 1986) which potentially could constitute a human safety risk. Collectively, the above-described considerations indicate that sGnRHa (Ovaplant®) is preferred choice for further evaluation and development as a candidate compound for a new animal drug approval for use to induce final gamete maturation in a variety of fish species.
The primary goal of field studies conducted under INAD #11-375 is to generate data to help determine appropriate Ovaplant® treatment regimens for inducing gamete maturation in a variety of cultured and wildstock fish species. Under this INAD, Western Chemical, Inc., is the sole authorized Ovaplant® supplier to all Investigators. The standard dose rate is between 10 – 75 microgram (µg) sGnRHa per kilogram (kg) body weight Administered IP or IM. However, a maximum dose of 150 µg sGnRHa per kg body weight is allowed in certain situations involving very small broodfish (e.g. fish <1kg bw). Treated fish are not allowed to be released or slaughter for human consumption (i.e., all treated broodfish must be maintained indefinitely or destroyed).
Please see the Ovaplant® study protocol for all cited references.
Collect supportive and pivotal data needed to establish the effectiveness of sGnRHa/Ovaplant® to induce gamete maturation in a variety of fish species.
Required Test Parameters
Investigator must collect data reporting percent ovulation and/or percent spermiation in treated fish. Investigator should also report general fish behavior and any adverse effects relating to treatment.
Restrictions on Use
Investigator must follow all instructions in the Study Protocol for INAD 11-375 regarding drug acquisition and handling, fish treatment and disposition, and data reporting requirements.
Standard dosage rate 10 - 75 microgram (µg) sGnRHa per kilogram (kg) body weight
Maximum 150 µg sGnRHa per kg body weight in certain situations involving very small broodfish (e.g. fish<1kg bw) < p>
No Release. All treated broodfish must be maintained indefinitely or destroyed.
Data Collection and Reporting
The following drug forms are intended primarily to provide Investigators a guide as to the type of data that must be collected during a study. In some cases, Investigators may deem the forms appropriate for the collection of raw data. However, it is extremely important to note that all data must be entered (and submitted) using the INAD Program Management System (online database). Drug Forms
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