Considerations for winter sheep nutrition discussed
In a Montana State University (MSU) Extension Sheep Program Facebook post published Nov. 21, MSU Extension revisits the research of V.M. Thomas and Dr. Rodney Kott, and provides a general overview of their work, which is still relevant for Western sheep producers today.
Thomas and Kott’s study, “A Review of Montana Range Ewe Nutrition Research,” was originally published in the Sheep and Goat Research Journal in 1995.
Seasonal nutrient requirements
To begin, MSU Extension’s summary notes protein is the number one nutrient requirement of sheep throughout fall and early winter months.
“Because fall grass is generally high in energy and lower in protein and moisture, it is important to supplement protein to feed the microbes digesting high-fiber grass,” reads the post. “Producers should focus on supplementing and not substituting.”
As sheep producers move deeper into the tough Western winter, MSU Extension explains nutrient requirements should focus more on forage availability than anything else.
The summary notes at this point in the year, range conditions have generally deteriorated and severe winter conditions can cause cold stress in the sheep herd. Because of this, ewes do not generally meet their nutritional requirements, so producers need to focus on matching their supplementation strategies with the pregnancy stage of their ewes.
Sheep pregnancy stages
Sheep body condition scores (BCS) are scored on a one to five scale, and a ewe’s 150-day gestation period is broken into three trimesters, 50 days each.
MSU Extension outlines an example of an operation that turns their bucks in on Oct. 15. They note flushing only works on thin ewes with a BCS of two or three, but producers should still supplement heavier ewes, especially if weather or feed conditions are poor.
Oct. 16 to Dec. 4 spans the first trimester and is deemed the early-gestation period, in this example. MSU Extension encourages producers to maintain the weight of their ewes during this time if they are in good condition with a BCS of three or higher. However, if BCS is below three, they recommend providing supplementation.
The second trimester, mid-gestation, of a ewe runs from Dec. 5 to Jan. 23. During this time, placental development occurs and brown adipose tissue is laid down in the lamb. MSU Extension encourages producers to maintain weight and condition in ewes with a BCS of three or better. During this time, it is critical ewes don’t lose any weight.
In this example, late gestation runs from Jan. 24 through March 14, and during these 50 days, rapid fetal and mammary development occurs.
“Ewes need to gain weight when shearing in mid- to late-February, and lambing will start around March 14,” the MSU Extension post reads. “A BCS around three to four is ideal. A BCS over four may lead to predisposed pregnancy toxemia and dystocia problems. A BCS below three can result in poor milk production and decreased lamb vigor.”
Supplementation recommendations
According to Thomas and Kott’s work, supplementation is generally a cost-effective practice for producers during winter months, and supplements fed at 0.2 to 0.3 percent of ewe body weight – or one-half pound supplement to every 175 pounds of sheep – will not reduce forage intake.
“Body condition when entering winter months influences ewe productivity and her response to supplementation,” reads the post. “Ewes in better shape can use supplementation more effectively.”
MSU Extension further notes producers should provide supplemental energy when range forage is available, winter weather is mild and they have ewes with a BCS of four or five that can afford to lose some weight. Comparatively, protein supplements should be provided when winter weather reduces forage intake and ewes cannot afford to lose any weight.
“Ewes can be supplemented on alternate days while grazing winter range,” they note.
Conclusions and take-aways
In summary, MSU Extension urges producers to sort and supplement young, old and thin ewes separate from the rest of the herd, noting tubs are a good option if weather and daily labor hinders daily supplementation.
“If ewes are stressed or a storm is coming, the best supplement is the one producers already have on hand, regardless of energy or protein needs,” reads the post. “Don’t cut back on supplement if the weather gets nice.”
Additionally, MSU Extension points out Thomas and Kott’s research found increased body weight gain does not always translate into increased economic returns when ewes in good body condition enter winter months, forage availability is good, winter weather is mild and ewes are fed adequately during late pregnancy.
Lastly, MSU Extension concludes inadequate ewe nutrition during the second trimester can disrupt growth and development of the placenta, resulting in low oxygen transfer to the fetus. If nutrient restriction during mid-gestation is severe enough, it cannot be made up for in late pregnancy.
Hannah Bugas is the managing editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
