Abstract
Simple SummaryAlthough a reduction in the number of sperm in the sperm storage tubule (SST) regions in older hens was hypothesized to relate to fertility, no comparison has been made to date on the effect of age (mature and old) on reproduction, the morphology of the sperm storage reservoir, the resident sperm in the UVJ, and the fertility duration in chickens. The present study indicated the morphological characteristics of reproductive organs did not differ between mature and old hens. The numbers of ovarian follicles were greater in mature hens. Significant differences in the sperm storage reservoir, such as the inner and outer diameter of the SSTs and epithelium height, were demonstrated. The number of resident sperm cells that were related to fertility periods was greater in mature hens than in old hens.The effect of age on fertility was investigated in Thai native chickens. The objective of this study was to determine the effects of age (mature and old) on the morphological characteristics of the reproductive organs and the histological characteristics of the uterovaginal junction (UVJ) tissues, resident sperm in the UVJ, and fertility duration in Thai native hens. We found no differences in the morphological characteristics of the reproductive organs, except for the number of follicles and the sizes of the fifth large yellow follicle in mature hens, which were greater than those in old hens (p < 0.05). The diameter of the sperm storage tubules (SSTs) epithelium was larger in old hens than in mature hens (p < 0.05), whereas the epithelium height was lower in old hens (p < 0.05). The number of sperm in the SSTs was greater in mature hens compared with old hens (p < 0.05). Mature hens showed a higher fertility rate than old hens. Our results suggest that, in old hens, the function of the SSTs is impaired, and sperm cannot be retained. Such a deterioration of the SSTs may be one of the factors involved in the decline in fertility.
Highlights
Flock fertility in chickens depends on both the males’ and females’ reproductive status, including factors such as sperm quality, behavior, egg quality, and animal age.Egg production begins when the hen reaches 18–22 weeks, depending on the breed and season [1]
76 virgin Thai native hens were divided into the following groups: 38 hens that were 35–39 weeks old, 38 hens that were 73–75 weeks old, and 12 roosters; the animals were raised in individual cages with standard feeding and management under natural conditions
It was hypothesized that the decline in the fertility of old hens was due to a decreasing sperm storage capacity [23]
Summary
Flock fertility in chickens depends on both the males’ and females’ reproductive status, including factors such as sperm quality, behavior, egg quality, and animal age. Egg production begins when the hen reaches 18–22 weeks, depending on the breed and season [1]. It is apparent that sperm penetration is greatly reduced, dependent upon the age of the flock [7]. The physiology of sperm from older males appears to be relatively unaffected in terms of fertilization and penetration abilities [7,8]. One major contributing factor to decreased sperm penetration is more pronounced in aged females due to the hens’ physiological status. The conditions that cause low sperm numbers or single sperm activity at the site of fertilization could be associated with reduced fertility
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