Lambing Management: UW Extension SheepTask Force webinar examines periparturient ewe management
On March 26, the University of Wyoming (UW) Extension Sheep Task Force held the second of two webinars in its Lambing Management Mini-Series.
The presentation featured comments on periparturient ewe management, including a look at ewe demands, nutritional strategies and research-based approaches to reducing metabolic stress around lambing, from UW Extension Sheep Specialist Dr. Whit Stewart and Dylan Laverell, former UW master’s student and current PhD candidate at Lincoln University in Lincoln, New Zealand.
Periparturient challenges
To begin, Stewart provides context about the periparturient period, which encompasses the time period directly before, during and after birth.
“We tend to think about lambing as the event, but biologically, lambing is really the beginning of the most demanding stretch in a ewe’s year,” Stewart explains.
He adds the periparturient period is one of the most demanding times in a ewe’s life and, therefore, proper management practices are key to ensuring health and longevity.
Stewart notes as a ewe begins to recover from lambing, lactation also increases dramatically. Although these are both natural processes, the combination of these factors can lead to stress, particularly with regard to nutrition.
Peak lactation usually occurs anywhere from 21 to 30 days after lambing, Stewart explains, and as ewes produce more milk to support their offspring, nutritional intake and energy output can sometimes become mismatched resulting in complications like declining body condition scores (BCS) and illness.
Negative energy balance
When a ewe is unable to consume enough feed to meet caloric requirements for body maintenance and raising her lamb, the result is a negative energy balance.
Stewart stresses the immense demands of the periparturient period mean a negative energy balance is a normal biological state to some extent following lambing, so producers should be able to recognize the signs and support the ewe through management practices during these times.
“Negative energy balance is normal and unavoidable until the ewe’s intake catches up,” he notes. “Proactive management matters because a lot of what drives a negative energy balance or decreasing BCS isn’t just lactation in itself, it’s everything else layered on top of it.”
In particular, Stewart emphasizes the importance of assessing BCS throughout the periparturient period and allocating feed accordingly, as well as reducing concentration of animals in enclosed environments like lambing sheds to limit the spread of disease.
In closing, Stewart reiterates the importance of continuing to assess BCS after lambing and allocating feed accordingly, making sure dietary contributions are adequate enough to incentivize intake in ewes.
He also provides advice on strategic management practices like accounting for weather-related stressors, providing access to highly-digestible feeds like soy hulls and processing hay to reduce particle size as ways of supporting ewe health and encouraging feed intake.
Nutrition considerations
Following Stewart’s comments, Laverell sheds additional light on meeting ewes’ nutritional demands and reducing metabolic stress during the periparturient period.
He also discusses risk factors for two common pregnancy related metabolic disorders – pregnancy toxemia and hypocalcemia.
To begin, Laverell shares statistics on lambing rates across the country compiled by the U.S. Department of Agriculture (USDA) which reflect a 20 to 30 percent increase in reported lambing rates in Western states including South Dakota, Utah, Wyoming and Montana.
Laverell attributes this increase, in part, to the implementation of indoor lambing management practices as well as an increase in twin and triplet litters.
Although increased litter size means more lambs and more profit, it also leads to increased pressure on ewes.
“Unfortunately, an in-
creased number of fetuses works antagonistically towards rumen size and volume, especially in the last trimester,” Laverell explains. “As we increase the number of lambs in the fetal space, we decrease the amount of feed a ewe can apprehend.”
With this, Laverell underscores Stewart’s comments about the importance of promoting good BCS leading up to lambing and providing nutrient dense feedstuffs.
Disease factors
Next, Laverell shifts his focus to risk factors and management strategies relating to pregnancy toxemia and hypocalcemia.
Pregnancy toxemia is caused by severe energy deficiency and tends to affect sheep during late gestation, usually the last two to four weeks of pregnancy.
Ewes with poor BCS heading into lambing and ewes carrying multiple lambs are at highest risk for toxemia, as energy requirements spike in late gestation without the corresponding ability to increase feed intake.
“When a ewe is not getting enough from her feed or is physically unable to eat more, her body starts breaking down fat for energy,” Laverell explains.
Hypocalcemia or milk fever is a sudden onset disease resulting from low levels of blood calcium as ewes work to produce milk and colostrum, and lambs finish growing in the final stages of pregnancy.
Pregnancy toxemia and hypocalcemia present with similar symptoms including excitability, muscle tremors and gait changes, but hypocalcemia is much faster acting and death often occurs six to 12 hours after clinical signs are first observed, Laverell explains.
He emphasizes combatting these diseases begins with proper management practices like maintaining and monitoring BCS leading up to lambing, providing ample clean bedding in lambing sheds and timing shearing in accordance with gestation to reduce stress on ewes in the final stages of pregnancy.
“As is the case with a lot of other things, the best way to manage pregnancy-related metabolic dysfunction is through prevention,” he concludes.
Grace Skavdahl is the editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
