Reproductive responses of rice field rats (Rattus argentiventer) following treatment with the contraceptive hormones, quinestrol and levonorgestrol

The rice field rat, Rattus argentiventer, is a significant pest of rice in Southeast Asia. Fertility control methods have the potential to provide safe and effective alternatives to control methods that often include indiscriminate use of rodenticides or electric barriers. The aim of this laboratory...

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Bibliographic Details
Published in:Integrative zoology 2022-11, Vol.17 (6), p.1017-1027
Main Authors: STUART, Alexander M., HERAWATI, Nur ‘Aini, RISNELLI, SUDARMAJI, LIU, Ming, ZHANG, Zhibin, LI, Hongjun, SINGLETON, Grant R., HINDS, Lyn A.
Format: Article
Language:English
Subjects:
Baits
Control methods
ecologically based rodent management
Edema
Epididymis
Females
Fertility
fertility control
food security
Hormones
Males
Motility
Palatability
pest
Rats
Rattus argentiventer
rice
Rice fields
Rodenticides
Seminal vesicle
Southeast Asia
Sperm
Spermatozoa
Uptake
Uterus
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Summary:The rice field rat, Rattus argentiventer, is a significant pest of rice in Southeast Asia. Fertility control methods have the potential to provide safe and effective alternatives to control methods that often include indiscriminate use of rodenticides or electric barriers. The aim of this laboratory study was to assess uptake of bait coated with different concentrations of the contraceptive hormones, quinestrol (E) and levonorgestrel (P), delivered alone and in combination (i.e. EP‐1) and determine the short‐term effects on reproductive parameters of adult male and female R. argentiventer. In Experiment 1, 2 concentrations of E, P, and EP‐1 (10, 20 ppm) were fed to groups of wild‐caught rats for 7 days. In females, both E and EP‐1 induced uterine edema. In males, EP‐1 reduced epididymis and seminal vesicle weights and lowered sperm motility. However, these responses were inconsistent due to low bait acceptance, especially with increasing concentrations. In Experiment 2, EP‐1 (0, 20, 50, 100 ppm) was administered by oral gavage daily for 7 days to male R. argentiventer. There were significant reductions in epididymal and seminal vesicle weights for all oral doses of EP‐1, in sperm counts for the 50 ppm dose, and in sperm motility for the 20 and 50 ppm doses compared to the control group. To select the optimum dose of EP‐1, we must address the poor acceptance of contraceptive‐coated baits by rice field rats. Further research is required to improve the palatability of EP‐1 and to test its uptake under field conditions. Following delivery of contraceptive hormones, quinestrol (E) and levonorgestrol (P) in combination (i.e. EP‐1), to rice field rats R. argentiventer, there were clear effects on the reproductive physiology of both males and females. In females, both E and EP‐1 induced uterine edema, and in males, there were significant reductions in reproductive parameters when EP‐1 was delivered orally. However, when E and EP‐1 were presented on milled rice to rats, bait acceptance was highly variable.
ISSN:1749-4877
1749-4869
1749-4877
DOI:10.1111/1749-4877.12598