Seaweed for Sheep?

By Diane Wells

Photo by Diane Wells.

North Ronaldsay is a 2.7-square-mile island north of Scotland's mainland. In 1839, its residents encircled their island with a stone wall. The goal was to keep native sheep off the island's arable land for the sake of more valuable, imported cattle. Since the sheep-dyke (as the locals refer to it) was built, North Ronaldsay sheep have subsisted almost entirely on seaweed and a scrap of higher ground considered wasteland. Today, there are roughly 3,700 of these small, fine-boned, hardy sheep on the island, grazing during low tide, ruminating at high tide. They are not only an example of how adaptive animals are, but how nutritive seaweed must be to sustain terrestrial life at a latitude equivalent to Newfoundland's.

This breed is an extreme example of how seaweed can become feed, but a number of folks believe there are nutritional benefits when ocean-born plants are part of a domestic animal's diet. Kelp meal is seaweed that has been dried at low temperatures and then ground or milled. Typical analyses reveal at least seven vitamins (A, B1, B6, B12, D, E and K); over 60 minerals (including calcium, magnesium, potassium, sodium, manganese and selenium); and 17 amino acids (including lysine, histidine and proline). It also contains protein, fat, carbohydrates, plant growth hormones and alginates. And, because this nutrition is in plant form, the nutrients are readily available and therefore readily absorbed.

There is plenty of anecdotal evidence that kelp meal improves sheep health. Testaments range from the reduction of white muscle disease in lambs to fewer parasites, more efficient feed conversion and better digestion. The proof, they say, lies in improved twin rates and growth rates. It is even believed to prevent shedding and improve wool quality. But is there solid scientific evidence that a sheep's health benefits from regular doses of kelp meal? While researching this topic, I came across at least five kelp meal-producing companies based in Washington, Maine, Nova Scotia and Iceland. All touted said benefits. Yet I struggled to find results of controlled studies supporting such claims. There have been a handful, but the research has suffered from small study group sizes, the use of different species of seaweed from study to study and short study durations. Also, the amount of seaweed included in the diet (10 to 30 percent of total diet) went far beyond what you or I would consider feeding. Which begs the question: Are the study results applicable?

We know that sheep, like any organism, can suffer from mineral and vitamin deficiencies. A lack of sulfur in the diet is indicated by a reduction in wool growth and the shedding of wool; a lack of selenium and vitamin E can lead to white muscle disease; and a lack of zinc can reduce a ewe's ability to reproduce. We know this. So, what it comes down to is: How much do you know about your sheep's nutrition? Have you submitted samples of your pasture for a nutrition analysis? What about your hay? Do they have access to a mineral mix or just salt? Do they exhibit all signs that they are healthy, fully functioning ruminants?

If you flounder when answering any of these questions, and if you're willing to spend the money and run your own micro-experiment, pick up a bag of kelp meal. I am willing to bet that one or more of your local feed stores carries it. Recommended amounts and methods for feeding vary depending on whom you talk to. If you offer once-a-day rations, mix in .5 to 2 ounces per ration per day. If your sheep are purely grass-fed, put it in a covered self-feeder, separate from any other self-fed mineral mix, and allow them to take as needed. I have also seen recommendations for replacing up to 30 percent of their feed with kelp meal, although these recommendations come from those who stand to benefit from your doing so.

Kelp meal may be particularly beneficial to sheep during the late fall, when the nutritional quality of forage dips, and during winter if their hay does not have a particularly glorious nutritional analysis. Folks claim (and this makes sense) that it will have the most impact on wool quality when introduced to the diet immediately after shearing. Let's see ... that's fall, winter, spring. What the heck, let's just feed it year-round. It couldn't hurt, right? Or could it?

Kelp meal does contain low levels of copper, and copper is one thing you have to watch out for with sheep because it readily accumulates in their liver. Although some breeds are more susceptible to copper, it is a necessary dietary component. A good rule of thumb is 5 PPM in a complete day's rations. If you go over 25 PPM, you're asking for trouble. Kelp meal contains anywhere from 3 to 6 PPM, but the trace element molybdenum is also present (one analysis reads 15.9 PPM), and that is significant because it forms what's referred to as an insoluble complex with copper, which in turn limits the amount of copper than can be absorbed by the animal. Sheep are more susceptible to copper toxicity when molybdenum levels drop below 1 PPM, but if it surpasses 10 PPM, a copper deficiency could actually come about.

I focused on sheep here, but the value of kelp meal as a feed supplement is being investigated on everything from shrimp and fingerling trout to sheep, goats, pigs, horses, and dairy and beef cattle. Stay tuned for future updates on this topic as I burrow through the literature in search of answers for you and me. Meanwhile, if you currently feed kelp meal to your livestock, do tell us your story at Farming's online forum, Your insight is always appreciated.

The author, a regular contributor to Farming, is a biologist who lives and farms in Vermont's Northeast Kingdom.