I’m cleaning off some things on my desk, and one is the slide deck & notes from a presentation by Dr. Robert Van Saun at the KHSI Expo last August. This was a fantastic presentation titled “Meeting the Nutritional Needs of Sheep to Promote Health and Performance.” He focused on pregnancy feeding. Those of you who know me well will recognize that this topic was right up my alley, especially on the subject of macro and micro element supplementation; and its health consequences.

Dr. Van Saun’s opening argument was that the late-pregnancy ewe is the most important animal on the farm. This is because she’s not only carrying this  year’s crop, but her own value as a farm asset as well. So, it’s really critical that we get it right in managing her nutrition.

He noted that fetal organs are formed in the first twenty days of gestation, and nutrition in those critical days impacts the quality formation of the kidney, lung, liver, and heart. We always talk about the importance of feeding ewes well in late gestation because in the last thirty days, those fetuses are growing like gangbusters. But, in that thinking, there is often an unspoken implication that you can get by with all sorts of sins while those fetuses are still tiny and in early formation. Not entirely true: tho ewes don’t need high caloric intake in early pregnancy, since the fetuses aren’t yet demanding a lot of energy; the fetuses do still demand good quality vitamin and mineral availability, and a reasonable source of protein.

Now, onto late gestation: he showed multiple charts showing how as the fetuses get bigger, and as there are more of them, the ewe can’t take in as much forage volume anymore, since her rumen is compressed. At the same time, the fetuses are demanding more and more protein, vitamins, minerals and energy. So we can see why this is an impending disaster for many ewes: she can’t take in enough to support those lambs, so she robs body reserves to pull it off. A profound but obvious fact: when lambs are born, they are all relatively the same size; so a ewe has to use the same amount of energy and nutrients to create them no matter how well or poorly she is fed (i.e. newborn size doesn’t dramatically adjust to account for differences in feeding). So, if the ewe is underfed either energy- or nutrient-wise, or both, what will be sacrificed is her body condition, the lambs’ organ development; and colostrum quantity and quality, which then impacts lamb robustness and immune response. And, a ewe in poor condition will produce less milk, echoing into lowered lamb growth to sixty days. We know it’s true, but it can’t be emphasized enough: penny-pinching on feed during gestation costs us much more later, in weak, sick and dying lambs; as well as ewes stressed beyond capacity, risking their own survival and longevity.

Also cited were two studies that showed that improving protein intake in late pregnancy improved GI immunity to parasites in ewes. Another talk on the same day mentioned how protein is critical to immune cell function; and that as we select for bigger, faster-growing lambs, we are selecting for lambs which allocate more protein to growth, thus robbing immune function. If we go too far, we start to get lambs that have great growth potential, but need a ton of deworming to keep them alive; because their immune systems can’t be relied-upon to combat parasite loads. So, probably the same is true of ewes: as we breed for ewes that have a propensity to produce multiple lambs with higher birth weights, we know she’s allocating more protein in that direction, and thus robbing her own immune cells. She’ll experience payback for this with a whopper of a worm load at the time she lambs, not to mention, laying down more worm eggs on the pasture for lambs to consume. Plus, consider that if the ewe is immune-compromised at lambing, she’s also more vulnerable to mastitis, pneumonia, and other bacterial infections so common during this time.

To prevent under-fed ewes during gestation, Dr. Van Saun encouraged careful monitoring of Neutral Detergent Fiber (NDF) measurements in feed; as this is the main controller of how much food a ewe needs to take in, versus can take in. We need feeds lower in NDF in late pregnancy, so that it’s ensured that the ewe can take in enough protein even tho she’s limited in how much volume she can eat. Other compensations would be grain feeding, or the use of protein tubs, to supplement for poorer quality hay with more nutrient-dense feeds.

The second part of the talk focused on macro and micro element minerals, and vitamins. Some interesting tidbits on this vein:

  • Inorganic selenium doesn’t cross into milk, so be sure ewes are supplemented with organic selenium leading up to and during lactation
  • Zinc is deficient in all forages, so forage is a poor source, we must supplement with a trace mineral salt if the sheep aren’t getting it from grain or other concentrate feeds. Zinc is the most important trace mineral; it’s responsible for 250 enzymes in the body!
  • Milk is low in iron, copper, selenium and zinc (zinc is marginal in milk). Placental transfer of these minerals happens instead, and the fetus concentrates them in his liver, to get him by until he starts eating and digesting feeds on his own. And, these minerals are concentrated in (well-made) colostrum. If you do lab analysis of fetal livers, you’ll see different concentrations of minerals than a liver from a lamb that’s been nursing for a while. If one has a lot of stillborns, it’s worth testing their livers, to assess whether a nutritional problem is contributing to the losses.
  • Fat-soluble vitamins do not cross the placenta (or do only very early in gestation). Vitamin A deficiency is a common cause of stillborns.
  • Copper, iron, zinc, selenium plus vitamins A and E are all very important to immune function. Lambs with weakened immune response have a) greater severity and duration of scours, b) more susceptibility  to pneumonia and c) a failure to build up an immune response to coccidia.

Next, Dr. Van Saun presented two interesting case studies he’d encountered locally in Pennsylvania that were nutrition-related.

The first was a farm that had a lot of ewes succumb to hypocalcemia, and a lot of lambs with fractured legs. The lambs were literally breaking their legs just from normal activity, like running and jumping! Forage analysis showed an “upside down” Ca : P ratio, as well as high potassium (K). Phosphorus and potassium both bind with calcium, making it non-bio-available.  The root cause was determined to be applying high amounts of fertilizer (NPK, remember?) to the forage/hay crop. It’s an important reminder that tho NPK pushes forage to greater  yield, it also skews the forage mineral-wise. In excess, it can create this devastating calcium deficiency.

The second case study was a 27% lamb mortality rate, plus a puzzling death of 24 out of 25 of the two-year-old ewes on the farm. Forage testing revealed low-normal copper levels, and very, very high molybdenum. Mo ties up copper. The root cause was determined to be that the family had fertilized the last two years with a limestone product. But not just regular limestone that we typically buy for fertilization; but rather a unique type that’s a by-product of mining activity in Pennsylvania. This by-product is much cheaper than standard limestone, but is also very high in Mo. So, the obvious impact was lambs which were copper deficient and struggled to thrive and survive.

But more interestingly, that the ewes born 2 years ago, bred for the first time as yearlings, fell apart and died after lambing. So, the nutritional impact to them likely traced alllllll the way back to their own fetal development, as well as their immune response. Remember that copper is important to both immunity, as well as organ development in the fetus in those first twenty days. So these ewes hadn’t formed properly in the womb, were deficient in copper their whole, young lives; culminating in the impact of ultimately killing them when they went into reproduction! Shut The Front Door! I loved this anecdote, because it vindicates copper as a critical nutrient in sheep, emphasizes how much we can pay if we don’t pay attention to minerals, and reminds us how being cheap with inputs (“bargain” fertilizer) in the short term often has long-term costs.

Ze bottom line: measure & manage NDF and protein in late pregnancy to ensure adequate intake for optimal fetal development and ewe body condition maintenance;  ensure good trace mineral availability and intake; and supplement with vitamins A, D and E when sheep are not on green grass. Good stuff!