The uterus of the pig is Y-shaped and bicornuate, with two long uterine horns and a moderately developed body that opens into the vagina through the cervix. Each uterine horn, measuring 10-12 inches in length, possesses a mucosal lining organized into characteristic spiral folds.
Function of Pig's Uterus :
The primary function of the uterus in pigs, like other mammals, is to provide a suitable environment for the development and protection of the fertilized eggs during pregnancy. The spiral folds in the uterine horns increase the surface area, offering a larger space for implantation and nourishing the growing embryos.
Estrus Cycle in Pigs :
Pigs exhibit a polyestrous reproductive cycle, meaning they can have multiple estrous cycles throughout the year. The estrous cycle in pigs lasts for about 21 days and is characterized by distinct phases:
1. Proestrus: This phase marks the onset of the estrous cycle and is characterized by increased activity and receptivity of the female pig to mating. It usually lasts for 2-3 days.
2. Estrus: During estrus, the female pig is most receptive to mating. The vulva becomes swollen and reddened, and she exhibits standing heat, where she stands motionless when mounted by a boar. Estrus typically lasts for 2-3 days.
3. Metestrus: After ovulation, the corpus luteum forms from the ruptured ovarian follicles and begins producing progesterone. This phase is associated with the preparation of the uterus for pregnancy and lasts for about 14 days.
4. Diestrus: If fertilization does not occur, the corpus luteum regresses, leading to a decline in progesterone levels. The uterine lining is shed, and the pig enters the diestrus phase. Diestrus lasts until the next proestrus phase begins.
Pregnancy and Gestation Period:
Upon successful fertilization, the pig enters the gestation period, which lasts approximately 114-118 days in pigs. The fertilized eggs implant in the spiral folds of the uterine horns, and the uterus expands to accommodate the developing fetuses.
Conclusion:
The uterus of pigs plays a crucial role in the reproductive process, providing a suitable environment for the development of embryos and fetuses during pregnancy. Understanding the structure and function of the uterus is essential for effective breeding and management practices in pig farming.