What stimulates labor in dogs? - briefly
The process of parturition in dogs is primarily regulated by hormonal changes. Specifically, the decline in progesterone levels and the subsequent increase in prostaglandins are the key stimulators that initiate labor.
What stimulates labor in dogs? - in detail
Labor in dogs is a complex process that involves numerous hormonal and physiological changes. The initiation of labor in dogs is primarily regulated by the interaction between two key hormones: progesterone and relaxin.
Progesterone, produced by the corpus luteum in the ovary, maintains pregnancy by suppressing the release of oxytocin from the pituitary gland. Oxytocin is responsible for stimulating uterine contractions during labor. As pregnancy progresses, the levels of progesterone gradually decrease, allowing for the secretion of oxytocin and the onset of labor.
Relaxin, also produced by the corpus luteum, plays a crucial role in preparing the body for delivery. It acts on the cervix, causing it to soften and dilate, which facilitates the passage of the puppies through the birth canal. Relaxin levels peak around day 50-60 of gestation, coinciding with the final stages of pregnancy when labor is imminent.
In addition to these hormonal changes, other factors can influence the onset of labor in dogs. The placenta produces estrogen and prostaglandins, which help to ripen the cervix and stimulate uterine contractions. As the fetuses grow larger, they exert physical pressure on the mother's body, further promoting the release of oxytocin and relaxin.
The exact timing of labor can vary among individual dogs and breeds, with gestation lengths ranging from 58 to 68 days. However, once the hormonal cascade is initiated, the process typically follows a predictable pattern, leading to the successful delivery of the puppies.