Coturnix coturnix japonica

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Scientific Article. Administration of pregnant mare serum gonadotropin to Japanese quail (Coturnix coturnix japonica): dose response over seven days and.
New Zealand Veterinary Journal 50(3), 115-121, 2002

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Scientific Article

Administration of pregnant mare serum gonadotropin to Japanese quail (Coturnix coturnix japonica): dose response over seven days and comparison of delivery by daily injection or osmotic pump JE Girling*§, EJ Bennett† and JF Cockrem†

Abstract

Introduction

AIMS: This study is part of a research programme that aims to develop a method of hormone treatment to stimulate breeding in female birds. The aims of this study were to compare dose rates and two different delivery methods, daily injection or osmotic pump, for hormone treatment of Japanese quail (Coturnix coturnix japonica) with pregnant mare serum gonadotropin (PMSG).

Our current research aims to develop a method of hormone treatment which will stimulate development of the reproductive system in birds that can be applied to breeding programmes for endangered bird species. We have chosen Japanese quail as our model species for several reasons: quail are readily available and easily maintained in captivity, quail mature after only 4–6 weeks, and they maintain small gonads when they are held on short days in cool temperatures (Wada 1993).

METHODS: PMSG (0, 5, 10, 20, 40 and 80 IU PMSG/day) was administered to 6-week-old Japanese quail housed under short-day, cool-temperature conditions (8L:16D at 7–10°C) by daily injections or osmotic pump for 7 days. Three additional groups were untreated: one group was dissected at Day 0, and two groups were maintained under either short-day, cooltemperature or long-day, warm-temperature (16L:8D, 20°C) conditions for 7 days. Cloacal diameter was measured daily, and ovarian and oviductal mass and plasma oestradiol concentrations measured at the end of the treatment period.

CONCLUSIONS: A dose of 10 IU PMSG/day was chosen for use in future experiments with Japanese quail, for the first 7 days of treatment. The delivery method of choice for future studies will depend on the practical considerations of the research in question.

The experiment described in this paper is one of a series using PMSG to stimulate reproductive development in the Japanese quail. PMSG, also known as equine chorionic gonadotropin, is a glycoprotein hormone of placental origin that has both luteinising hormone (LH) and follicle stimulating hormone (FSH) -like actions in non-equid species. PMSG has been commonly used to simulate out-of-season breeding, and to increase ovulation rate and litter size in mammals (Thimonier 1981; Esbenshade et al 1990; Shelton 1990; Haresign 1992; Hoppen 1994), and has been used for a variety of purposes in birds. In laying birds, PMSG has been used to stimulate premature ovulation (Fraps et al 1942). However, if laying birds are treated with PMSG over an extended period of time, the normal process of ovulation can be disrupted (Fraps and Riley 1942; Johnson et al 1985). Administration of PMSG can also be used to stimulate development of the reproductive tract and egg production (Opel and Nalbandov 1961; Zadworny and Etches 1988; Wakabayashi et al 1996; EJ Bennett, M Kikuchi and JF Cockrem, unpublished). However, the growth of ovarian and oviductal tissue in response to PMSG is highly variable among individual females and treatment can lead to ovarian growth without a normal hierarchy of developing follicles. Variation in response is a feature of hormone treatments that could, in part, be due to the differences in hormone action between exogenous PMSG and natural avian gonadotropins, and could be related to dosage of PMSG used. Seven days is too short a period to allow development of a full hierarchy of ovarian follicles in response to PMSG, but is sufficient time to assess effects of PMSG dosage on ovarian and oviductal growth.

KEY WORDS: Japanese quail, Coturnix coturnix japonica, PMSG, daily injections, osmotic pump, ovary, oviduct

Ideally, avian gonadotropins should be trialled in experiments stimulating reproductive development in birds. However, unlike

* Centre for Women’s Health Research, Monash University, Department of Obstetrics and Gynaecology, Clayton VIC 3168, Australia † Conservation Endocrinology Research Group, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand § Author for correspondence. Email: [email protected]

8L:16D 16L:8D FSH FTS GnRH LH PMSG

RESULTS: PMSG treatment stimulated ovarian and oviductal growth. After 7 days of treatment with 10–20 IU PMSG, ovarian and oviductal mass were similar to those in birds moved from short to long days. Females treated with the highest doses of PMSG (40 or 80 IU) had significantly larger cloacal diameters and ovarian and oviductal mass than other treated birds or birds maintained under long-day, warm-temperature conditions. Daily injections and osmotic pumps were equally effective methods of delivery. However, there was considerable variation in response to PMSG among individual birds and this was particularly obvious at the higher doses (20–80 IU PMSG). There were no differences in plasma oestradiol concentrations between groups treated using daily injections or osmotic pumps.

8 h light:16 h dark 16 h light:8 h dark Follicle stimulating hormone Friedman’s test statistic Gonadotropin-releasing hormone Luteinising hormone Pregnant mare serum gonadotropin

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New Zealand Veterinary Journal 50(3), 2002

PMSG, which is readily obtainable at a relatively low cost, avian gonadotropins are not commercially available, and are not available for research use in sufficient quantity for studies of hormonal stimulation of reproductive development. In addition to trials with PMSG, parallel studies are currently being conducted using avian gonadotropin-releasing hormone (GnRH) and GnRH antagonists. The method used to administer PMSG is also important. Previous experiments have used either daily injections (e.g. Imai et al 1972; Johnson et al 1985; Petitte and Etches 1989) or the implantation of an osmotic pump (Wakabayashi et al 1992, 1996) to deliver hormone. Both methods have their advantages and disadvantages. Implantation and removal of an osmotic pump requires an invasive surgical procedure and anaesthesia. Injections are considerably less invasive, but they require regular capture and handling of birds. If an osmotic pump is implanted, hormone is delivered regularly throughout the day, whereas daily injections result in variable hormone levels in the blood. Daily injections, however, allow the dose of hormone to be easily varied on a daily basis and between birds. The aims of the current experiment were to compare the effects of (a) varying doses of PMSG and (b) different methods of PMSG delivery, daily injections or osmotic pump, on cloacal diameter, ovarian and oviductal mass, and plasma oestradiol concentrations in quail over 7 days.

Materials and Methods Birds

Quail (n=105) were purchased at 3 weeks of age from Rangitikei Game Birds Ltd (Bulls, New Zealand). Birds were held in individual cages under short-day, cool-temperature conditions (8L:16D, 7–10°C) until the experiment was started when birds were 6 weeks old. Short days and cool temperatures prevent sexual maturity in Japanese quail (Wada 1993). Birds were provided with food (quail pellets, Unifeed Ltd, Palmerston North, New Zealand) and water ad libitum. Cloacal diameter was measured every second day from the time of purchase until the experiment began and daily during the experimental period. All experimental procedures were approved by the Massey University Animal Ethics Committee (Palmerston North, New Zealand). Experimental design

At 6 weeks of age (body mass approximately 200g), birds were allocated into 15 separate treatment groups (n=7, unless otherwise stated). Variations in sample size among groups were due to incorrect sexing of juvenile quail, the limited number of osmotic pumps available for implantation, or complications due to pump implantation (see below). One group was killed on the day treatment started (Day 0). A second group was maintained under short-day, cool temperature conditions (8L:16D, 7–10°C) without treatment (n=9), and a third group was transferred to long-day, warm temperature conditions (16L:8D, 20°C) to determine the ovarian and oviductal development in 7 days under stimulatory environmental conditions. Birds from the remaining 12 groups were maintained under short-day, cool temperature conditions and received either 0, 5, 10, 20, 40 or 80 IU PMSG/ day via daily injection, or 0 (n=3), 5 (n=5), 10 (n=6), 20 (n=5), 40 (n=4) or 80 (n=5) IU PMSG/day via osmotic pump. Sham (0 IU PMSG) injections and pumps contained vehicle solution only.

Girling et al

The osmotic pumps (Alzet, Model 2001; Alza Pharmaceutical, Palo Alto CA, USA) were designed to release their contents at 1 µl/h over a 7-day period at a body temperature of 37°C, and were filled as described by Wakabayashi et al (1996). The doses used in this experiment assumed this flow rate (as per Wakabayashi et al 1996). Osmotic pumps were implanted subcutaneously after local anaesthesia using lignocaine hydrochloride USP at 10 µg/g body mass. A small incision was made on the left ventral surface of the abdomen and pumps implanted beneath the skin. The wound was closed using small tissue clips (Autoclip, Becton Dickinson, USA) and topical antibiotic cream applied (Bactroban, Smith Kline Beecham). Birds were withdrawn from the experiment if the tissue clips failed to maintain the pump in position. At the completion of the treatment period, quail were killed by stunning followed by decapitation, and a blood sample was collected. Birds were dissected and ovaries and oviducts removed and weighed. Blood samples were centrifuged and plasma was harvested and stored at –20°C until assayed for oestradiol by radioimmunoassay. Radioimmunoassay

Thawed plasma was extracted once with re-distilled dichloromethane and reconstituted in phosphate buffer after drying down solvent extracts. Samples were extracted in three separate extraction runs; percentage recovery of oestradiol in spiked plasma using this procedure ranged from 91.4% (SD 4.7) to 99.0% (SD 3.5). Plasma oestradiol concentrations were corrected for extraction recovery factors. Extracted samples were analysed in duplicate using an oestradiol radioimmunoassay validated for quail plasma. Tritiated label (TRK322) was obtained from Amersham (UK) and the antibody (41-12) was provided courtesy of Dr RJ Etches (University of Guelph, Canada). Cross reactivity of the antibody was: oestradiol17α