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| Livestock Research for Rural Development 20 (11) 2008 | Guide for preparation of papers | LRRD News | Citation of this paper |
This study was carried out to investigate the effects of long term exposure of low doses of BPA, o, p’- DDT or both on sexual maturity in post-hatching Japanese female quail. Forty-six post-hatched females Japanese quail were used in this study. The quail were divided into 5 groups; the first group (n=9) did not receive any treatment and kept as a control; the second group (n=10) received only 10 µl corn oil orally for 60 days; the third group (n=6) orally treated daily for 60 days with 2 mg of BPA in 10 µl corn oil; the fourth group (n=10) administrated 20 µg of o, p’-DDT in corn oil, while the fifth group (n=11) received 2 mg of BPA and 20 µg of o, p’-DDT in corn oil as a mixture (Mix) for the same period. The onset of sexual maturity in females was observed. The egg weight and eggshell thickness were measured at the end of the experiment. The livers and shell glands of the control and all treated birds were collected and prepared for histological examination.
There were no significant differences among control and treated females in body weight, egg weight and eggshell thickness. However, sexual maturity was significantly delayed in treated females with BPA, o, p’- DDT and Mix compared to control and oil treated ones. The liver histology showed no pathological lesions in all treated groups as well as the control ones. Shell gland of one female of the Mix group (BPA and o, p’- DDT) showed smaller and fewer tubular gland compared to control shell gland. The sexual maturity of this female was distinctly delayed. In conclusion, BPA, o, p’- DDT or a mixture of both might delay the sexual maturity in female quails when administrated in post- hatching period for successive 60 days of age.
Key words: bisphenol, DDT, post-hatching quail
Plastics and pesticides are examples of products that contain oestrogenic endocrine- disrupting chemicals (EEDCs), which can interfere with mammalian development by mimicking the action of the sex hormone. For instance, the exposure of developing rodents to high doses of EEDCs advances puberty and alters their reproductive function. Low environmental doses of EEDCs may also affect development in humans. Effects have become apparent in humans over the past half century that are consistent with those seen in animals after exposure to high doses of EEDCs, such as an increase in genital abnormality in boys and earlier sexual maturation in girls. Exposing female mouse fetuses to an EEDC at a dose that is within the range typical of the environmental exposure of humans alters the post-natal growth rate and brings on early puberty in these mice (Howdeshell et al 1999).
Low levels of Bisphenol A (BPA) have also been found to cause biological effects, and its mode of action appears to mimic that of the female hormone, oestrogen. BPA has been reported to be weakly estrogenic, both in vitro and in vivo. Krishnan et al (1993) found that BPA leaching from polycarbonate flasks could compete with estradiol for binding to estrogen receptor in rat’s uterus, inducing production of progesterone receptors and promoting proliferation of cultured human mammary cancer cells. The estrogenicity of BPA in vitro was reported to be approximately 15,000 times less potent than 17β- estradiol (Gaido et al 1997). While Kuiper et al (1998) demonstrated that BPA could interact with both α and β- estrogen receptors. Because of the weak estrogenicity of BPA and possible daily human exposure to BPA, its potential role as an endocrine disruptor is of great concern.
Environmentally relevant doses of o, p’- DDT causes mullerian duct malformation and ovotestis formation in gull embryos (Fry et al 1987). Moreover, in ovo exposure to o, p’- DDT caused production of shellless or soft-shelled eggs in adult quail (Bryan et al 1989). The presence of DDT in wild bird eggs has been associated with decreased reproduction, eggshell thinning and oviductal malformation (Fry et al 1987). Reproductive failure due to eggshell thinning has been associated with high concentrations of DDT and its persistent metabolite, DDE, in wild birds (Bignert et al 1995). Mechanism of eggshell thinning might be attributed to the disturbance in carbonic anhydrase. Reports have shown that adult exposure to a carbonic anhydrase inhibitor decrease eggshell quality (Lundholm 1990).
In mammals BPA could enhance the age of puberty in females, however, little is known about the effect of BPA and o,p’- DDT or both on sexual maturity in female quails. The purpose of this study was to determine if the onset of sexual maturity of female Japanese quails would alter when quails were exposed to BPA and o,p’- DDT at early stage of life and to what extend these chemicals might affect the eggshell thickness of treated quails.
Forty-six post-hatched females Japanese quail were used in this study. The age of the quail at the start of the experiment was one week. The quail were divided into 5 groups; the first group (n=9) did not receive any treatment and kept as a control; the second group (n=10) received only 10 µl corn oil orally for 60 days; the third group (n=6) orally treated daily for 60 days with 2 mg of BPA in 10 µl corn oil; the fourth group (n=10) administrated 20 µg of o, p’-DDT in corn oil, while the fifth group (n=11) received 2 mg of BPA and 20 µg of DDT in corn oil as a mixture, daily for the same period. The quail fed a diet and supplied with water ad libitum. The quail maintained on 14 hours light and 10 hours darkness at 25 ºC.
Body weight of females was conducted twice (Day 45 and 55). The rate of female growth was evaluated. The egg weight and eggshell thickness measured at the end of the experiment (Day 60). Quail’s eggs production were observed daily and any irregularities of the female egg production in addition to any abnormal eggs (cracked and shell less eggs) were collected daily.
Date to sexual maturity was calculated as the day from hatching to the day of first egg production. The date of sexual maturity (the first egg production) was observed and noted in control and treated quails.
The livers and shell glands of the control and all treated birds were collected and prepared for histological examination.
Body weight, data of the female sexual maturity, egg weight and the eggshell thickness were analyzed using one- way ANOVA followed by Duncan’s test. The percentage of egg thinning was calculated as the difference between the average of eggshell thickness in control bird and treated birds subdivided by the average of egg shell thickness in control bird.
The body weight of all females under this study was measured twice at Day 45 and 55 of the experiment. There were no significant difference between all females in body weight moreover, all female increase in weight by time of the experiment (Table 1).
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Table 1. Body weight (g), egg weight (g), egg shell thickness (mm) and date of sexual maturity (Mean± SEM) of control and treated female during the experimental period |
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Parameters |
Different groups |
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Control |
Oil |
BPA |
DDT |
Mix |
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Body weight at day 45 |
124.6±4.1 |
126.0±1.8 |
121.4±5.8 |
113.5±2.3 |
120.3±4.3 |
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Body weight at day 55 |
136.2±1.6 |
139.3±2.2 |
135.9±3.3 |
135.7±2.9 |
131.6±3.8 |
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Egg weight at day 60 |
10.0±0.2 |
9.7±0.2 |
9.7±0.1 |
9.7±0.2 |
9.6±0.2 |
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Eggshell thickness* at day 60 |
0.22±0.01 |
0.21±0.01 |
0.21±0.01 |
0.20±0.01 |
0.21±0.01 |
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†Date to sexual maturity |
47.1±0.9a |
48.0±0.4a |
49.7±1.7b |
52.3±0.8b |
50.0±1.9b |
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†. Date to sexual maturity was calculated as the day from hatching to the day of first egg production. Values with different superscripts are significantly different (P<0.05). *DDT treated group exhibited a significantly decrease (P<0.05) in eggshell thickness compared with control ones (Student t-test) |
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Both parameters were measured at the end of the experiment (Day 60). No significant difference was noted in egg weight of all females group. However, in term of eggshell thickness, using one way- ANOVA revealed that there was no significant difference among female groups (Table 1). However, when we compared each group separately with the control one using student t-test, DDT treated group exhibited a significantly decrease in eggshell thickness compared with control ones (P<0.05).
Sexual maturity was significantly delayed in treated females (BPA, o, p’- DDT and Mix) compared to control and oil treated ones (Table 1).
The liver histology showed no pathological lesions in all treated groups as well as the control ones. Shell gland of one female of the Mix group (BPA and o, p’- DDT) showed smaller and fewer tubular glands in compared with control normal shell gland (Figure 1).
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The female sexual maturity was distinctly delayed compared to control females, moreover, it showed egg irregularities after the sexual maturity.
Adverse reproductive outcomes in various animal species treated with or exposed to dichloro-diphenyl-trichloroethane (DDT) have been linked to the hormone mimicking properties of the parent chemical and its derivatives (Vos et al 2000). Reviews of studies, which deal with the ingestion of DDT and its metabolites by natural and laboratory avian populations cautiously, conclude that there is a causal relationship between the ingestion of DDT and population debilitation (Cooke 1973).
Body weight of all treated groups measured at different periods after starting of the experiment was not significant to control females. This results in consistent with Halldin et al (2003) who found that body weight was not affected with the treatment of o, p’- DDT after in ovo exposure. The egg weight and eggshell thickness in this study were not significantly different in treated birds when compared to control ones. However, when we compared the eggshell thickness of o, p’- DDT treated group with the control, it showed a significantly (P<0.05) decreased in egg shell thickness. Several studies stated that eggshell thinning was found as a sequences of o, p’- DDT administration. Reproductive failure due to eggshell thinning has been associated with high concentrations of DDT and its persistent metabolite, DDE, in wild birds (Bignert et al 1995). Mechanism of eggshell thinning might be attributed to the disturbance in carbonic anhydrase. Reports have shown that adult exposure to a carbonic anhydrase inhibitor decrease eggshell quality (Lundholm 1990). It was reported that lipophilic compounds that can bio-accumulate in lipid tissues (Cotham and Bidlemen 1991). However, BPA showed no effect on the previous parameters and this may be due to high systemic clearance of BPA after its administration, which leads to the conclusion that BPA, is unlikely to accumulate in rats (Yoo et al 2000). There was a controversial reports concerning reproductive parameters in quail after DDT administration, Cross et al (1962) found that C. coturnix, which was fed DDT for a maximum of 55 days, showed no decrease in egg number or weight when the concentration of pesticides in the food was lower than 300 ppm. However, Smith et al (1968) reported that feeding of DDT ranging from 0, 100, 200, 400 ppm for 60 days had no effect on average egg production. Some studies were performed during the embryonic life (egg injection) and the effects of such chemicals were tested during the post-natal life. Following embryonic exposure to BPA on the Day 3 of incubation, sexually mature female were examined for egg laying and oviduct morphology. BPA (200 µg/g egg) or (67µg/g egg) had no significant effects on the number of egg produced as compared with control. There was a higher frequency of females with a retained right oviduct in groups treated with BPA (Halldin et al 2001).
There were a significantly delayed in sexual maturity of o, p’- DDT, BPA and Mix treated groups. It was reported that Japanese quail (39 day of age) had a lag in egg production when given a diet containing 100 ppm o, p’- DDT for 45 days (Bitman et al 1969). Egg laying was severely impaired in treated females after in ovo exposure to 2 mg/egg of o, p’- DDT, however, all treated females had ovaries that appeared unaffected upon necropsy as compared to the ovaries of the control birds (Halldin et al 2003). The in ovo exposure caused retention of right oviducts and decreased the length of left oviducts. Moreover in rats, o,p'-DDT reduced sexual behavior. The behavioral effects of o,p'-DDT were consistent with its putative estrogenicity. o,p'-DDT might act centrally to interfere with endogenous estradiol priming of sexual behavior (Uphouse and Williams 1989). One female bird in this experiment showed a decrease in number of tubular gland of the shell gland. The sexual maturity of this female was delayed and irregularities in egg production were noticed thereafter. Halldin et al (2003) found that after in ovo exposure to 2 mg/egg of o, p’- DDT, the treated bird after grown to adulthood showed a fewer tubular glands of the shell gland compared to control non treated.
In conclusion, the present experiment concluded that BPA, o, p’- DDT or a mixture of both chemicals could induce a delayed in sexual maturity in treated female quails, when administered early after hatching until 60 days of age.
We would like to express our sincere gratitude to Professor Dr. Y. Yoshimura, Graduate School of Biosphere Science, for his generous help during the experiments of this study, and his critical comments and suggestions.
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Received 3 August 2008; Accepted 8 August 2008; Published 6 November 2008
