Farrowing is the process of a pig giving birth. Understanding the timing and progression of farrowing is fundamental for animal well-being and the survival of newborn piglets. Pig reproduction involves a short, predictable gestation period followed by rapid labor. Distinct biological cues signal the impending birth, allowing observers to prepare for the arrival of a litter.
Calculating the Gestation Period
A sow’s pregnancy is consistent, lasting an average of 114 to 115 days. This duration is commonly summarized by the mnemonic “three months, three weeks, and three days.” The typical range for a full-term delivery is 112 to 120 days from the date of successful breeding.
Farrowing is initiated when maturing fetuses begin to outgrow their placental nutrient supply, causing a hormonal cascade in the sow. Litter size can slightly influence this timing. Sows carrying large litters may farrow slightly earlier, while those with smaller litters might experience a slight delay.
Environmental and genetic factors, such as the sow’s breed and age, contribute to minor variations in gestation length. Knowing the exact breeding date is important because it allows producers to pinpoint the expected farrowing day (the 114th day). This ensures the sow can be monitored closely during the final week.
Signs That Farrowing Is Imminent
Specific physical and behavioral changes allow for accurate prediction of farrowing, usually within 12 to 48 hours. The most reliable physical indicator is the development of the mammary glands and the onset of milk production. When milk can be easily expressed from the sow’s teats, birth is less than 12 hours away.
Behavioral signs, driven by the nesting instinct, often begin up to a day before labor starts. The sow becomes restless, frequently standing, pacing, and lying down while attempting to find a suitable birthing location. She may also exhibit rooting behavior, using her snout to rearrange bedding material to construct a nest.
As delivery approaches, the sow’s respiration rate increases significantly, sometimes rising from a normal resting rate of about 20 breaths per minute to over 60. Physical examination may also reveal swelling and reddening of the vulva, accompanied by a mucous discharge. These collective signs alert observers that the preparatory stage of labor has begun.
The Farrowing Process and Piglet Survival
The actual farrowing process generally takes between two and four hours in a healthy sow. However, in modern lines selected for large litter sizes, the process can extend up to six or eight hours. Piglets are typically born at intervals of 15 to 20 minutes, though this timing fluctuates throughout labor.
A prolonged birth interval between piglets increases the risk of stillbirth due to oxygen deprivation during contractions. Contemporary sows often deliver litters exceeding 15 piglets. Once the entire litter has been delivered, the sow expels the placental membranes, usually within a few hours.
The immediate post-farrowing period is demanding for newborn survival, with the first 72 hours being the most critical. Piglets must be dried quickly and kept warm, as they are highly susceptible to hypothermia. The most important factor for long-term health is the prompt intake of colostrum, the antibody-rich first milk. Piglets that manage to stand and suckle within 30 to 45 minutes of birth have a higher survival rate, as colostrum provides necessary passive immunity.