Sheep farming is a huge part of agriculture around the world, providing us with meat, wool, and even milk. And a key part of successful sheep farming is understanding how sheep reproduce.
The gestation period in sheep – that is, the length of the pregnancy – is an important time for both the ewe (the mama sheep) and the lamb she’s carrying. This article will cover all things related to the gestation period sheep experience, including:
- How long sheep are pregnant
- Factors that can affect the gestation period
- Hormonal changes during pregnancy
- Nutritional needs of pregnant ewes
- Common diseases during pregnancy
- How to prepare for lambing season
Gestation period length and influencing factors
Once a ewe has successfully bred, how long will she be pregnant?
Average gestation length
Sheep are typically pregnant for about 21 weeks, which works out to around 147 days. That said, the precise length of a ewe’s pregnancy can vary a bit, depending on several factors.
Factors affecting gestation length
- Breed. Certain breeds of sheep tend to have slightly shorter or longer pregnancies than others.
- Nutrition. Adequate nutrition during pregnancy is important. If a ewe isn’t getting enough to eat, it could extend her pregnancy slightly.
- Age. Younger ewes sometimes have slightly longer gestation periods.
- Number of fetuses. If a ewe is carrying multiple lambs, she’s likely to have a shorter pregnancy. The more lambs she’s carrying, the shorter the pregnancy is likely to be.
- Environmental temperature. Extreme temperatures can also affect how long a ewe will be pregnant.
Hormonal changes during pregnancy
Hormones are critical for a sheep’s pregnancy.
- Oestrogen: Oestrogen levels increase as the pregnancy progresses, getting the ewe ready to give birth. It promotes uterine growth and the development of the mammary glands.
- Progesterone: Progesterone is necessary to maintain the pregnancy and prevent uterine contractions. Levels stay high throughout gestation.
- Cortisol: Cortisol contributes to fetal development and starts the birthing process. Monitoring cortisol levels can help you manage stress in ewes, which is important for a successful pregnancy.
Nutritional needs during gestation
Proper nutrition is critical for a ewe’s successful pregnancy and the healthy development of her lambs. The right nutrition leads to healthy birth weights and helps keep the ewe healthy before, during, and after lambing.
Trimester-wise nutritional needs
A ewe’s nutritional needs change as the pregnancy progresses:
- First trimester: The lambs aren’t growing much at this stage, so the main goal is to maintain the ewe’s condition. It’s important to keep her at a healthy body condition score (BCS).
- Second trimester: The lambs are growing faster now, so the ewe needs more nutrients, especially protein and energy, to support their growth.
- Third trimester: This is when the lambs grow the most rapidly — about 75% of their growth happens in the last trimester. At the same time, a ewe’s appetite can decrease by as much as 30%, so it’s crucial that what she does eat is packed with nutrients.
Nutritional supplies
Here are some key elements of a pregnant ewe’s diet:
- High-quality pasture: Spring grass is an especially good source of nutrients during the last trimester. Fresh, nutritious pasture should be available whenever possible.
- Supplementary feeding: In many cases, especially in late gestation, ewes need more than pasture can provide. Hay, silage, or concentrate feeds can supplement the ewe’s diet.
- Water: Fresh, clean water should always be available. Water is essential for all of the ewe’s metabolic processes during pregnancy.
Common diseases during pregnancy
Like any mammal, ewes can develop certain diseases during pregnancy. Here are two common ones:
Ovine Pregnancy Toxaemia (Twin Lamb Disease)
Twin lamb disease is a metabolic disease that usually strikes in late pregnancy, especially in ewes carrying more than one lamb. It’s especially common in lowland flocks with ewes gestating twins or triplets.
The cause? Not enough energy intake, which leads to fat stores being mobilized and ketones being produced. Ewes with twin lamb disease may be lethargic, lose their appetite, and show neurological signs.
To prevent twin lamb disease, make sure your ewes are getting enough energy, especially in late gestation. Regularly monitoring their body condition score (BCS) can help you keep track.
Hypocalcaemia (Milk Fever)
Also a metabolic disease, milk fever occurs in late gestation or early lactation when blood calcium levels plummet. It generally happens during the last six weeks of gestation or the first month of lactation.
Milk fever is triggered by increased calcium demand for fetal skeletal development or milk production. Muscle weakness, tremors, and recumbency (an inability to rise) are all symptoms of the disease.
You can prevent milk fever by making sure your ewes have enough calcium in their diet and by avoiding sudden changes in their diet.
Preparing for Lambing Season
If you’re raising sheep, getting ready for lambing season is critical for a positive outcome. Here’s what you should do:
- Vaccinate. Vaccinate your ewes, especially in the last four weeks of gestation, to prevent common diseases.
- Monitor. Watch your ewes carefully for signs that they’re getting ready to give birth. This includes udder development, vulvar swelling, and restlessness.
- Prepare a lambing area. The area should be clean, dry, and protected from the elements. Provide plenty of bedding and enough space for the ewes and their lambs.
- Colostrum. Lambs need colostrum within the first few hours of life. This “first milk” provides important antibodies that protect them from disease.
In Conclusion
To sum things up, a sheep’s gestation period is affected by many things, so it’s essential to manage their nutrition, health, and environment with care.
Successful lambing depends on understanding and meeting the needs of pregnant ewes, so farmers can look forward to healthy lambs and productive flocks.