Monday, January 29, 2018

Sheepherder CSI

About 10 days ago, while I was making my morning check of the breeding flock and feeding the livestock guardian dogs, I came upon a ewe (one of our daughter's) who was obviously not doing well. She was off by herself (which our sheep typically do only when sick or giving birth). As I watched her lay down from 75 yards away, she looked uncoordinated. When I approached her, she failed to get up and move away - and when I did get her up, she staggered a few steps and fell over. This prompted an immediate call to the veterinarian (who also happens to be my wife). As the ewe was only about a month away from giving birth, Sami decided to come check on her. We determined that she had a fever, and Sami noted a fair amount of nasal congestion. We also noticed that she was turning her head to the left and grinding her teeth. While Sami couldn't be certain, she suspected a combination of an upper respiratory infection and perhaps ovine polio (caused by a Vitamin B deficiency). Sami treated her and we slowly walked her up the hill to the corrals, where we left her in a pen by herself. Later in the day, Sami checked on her and reported that she seemed about the same. We decided we'd haul her home so we could watcher more closely. By the next morning, she was dead - as were the two lambs she was carrying.

When we experience an unexplained death loss, especially this close to lambing, we often take the dead animal to the California Animal Health and Food Safety (CAHFS) Lab at the UC Davis School of Veterinary Medicine. Not only is it cheaper to have an autopsy performed on a dead sheep than it is to have the rendering company remove the animal, we often get valuable information. In the case of this particular ewe, we found out that she died of an unusual case of meningitis (a rare condition in mature sheep). While we were reassured that she didn't have a condition that was likely to spread to the rest of the flock, an additional (and unrelated) finding did concern us. In checking her liver for heavy metals, the pathologist at CAHFS found that she had elevated copper levels (she had 260 ppm of copper; the high end of normal is 100). Copper is an essential micronutrient for sheep, but excess copper can be extremely toxic. Sheep store copper in their livers. When sheep undergo some type of stress (like a difficult lambing, harsh weather, or abrupt change in diet), their livers shed this copper into their bloodstream, often with fatal consequences.

When we read the results, we obviously became concerned about the copper levels in the rest of the flock. If this ewe had elevated copper, it was entirely possible that other ewes may have elevated levels as well. If so, we might have problems during lambing. Sami and I, along with our partner Roger, immediately went into Sheepherder CSI detective mode. Roger and I began researching possible sources of copper, as well as potential treatment options. Sami and I made plans to draw blood samples from a subset of the ewes.

Fortunately, I also placed a call to a friend who is on the faculty at the Vet School. Dr. Bret McNabb is a very experienced and knowledgeable large animal clinician and teacher. He told us that blood tests would not be a good indicator of copper status - we'd need more expensive liver biopsies. He also told me that he usually didn't see copper-related deaths until liver levels were above 400 ppm. He encouraged us instead to continue looking for potential sources of copper in our flock's diet, and to send any additional fatalities to the CAHFS lab. We also talked about treatment options, which included providing supplemental molybdenum to bind the copper that the ewes had already stored.

With Dr. McNabb's reassurance, we turned our focus to sources of dietary copper. We have a couple of suspects:
  1. The annual grasses that feed our sheep this time of year likely have some copper in them. Roger went back through some forage tests from the Sierra Foothill Research and Extension Center and found that at some times of the year, the forage may contain slightly more copper than the sheep need.
  2. For at least half the year, our sheep graze on land that was once in orchards. Copper sulfate may have been used as a dormant spray on this land; we may have residual copper in the soil. Our next step will be to test the forage for copper during the grazing season (spring, summer and early fall).
  3. We utilize surface water  to irrigate our summer pastures and to provide drinking water to the sheep during most of the year. To control algae in their canals (which can clog our sprinklers), our water agency uses one of several aquatic herbicides in which copper is an active ingredient. While both products are labeled as safe for livestock consumption, this may be something we need to investigate further.
  4. As Dr. McNabb pointed out, sometimes feed manufacturers make mixing errors. For example, the mineral mix we provide to our sheep does not have any added copper. However, mistakes can happen. This weekend, we sent a sample of our mineral mix to CAHFS for analysis. We should know the results by the end of this week.
  5. The weed common groundsel (Senecio vulgaris) contains a liver toxin that apparently inhibits the liver's ability to metabolize copper. We know we have common groundsel in areas where the soil has been disturbed, and we know the sheep will graze it on occasion. However, according to Toxic Plants of North America (Burrows and Tyrl 2001), sheep and goats are less susceptible to common groundsel than other livestock - and can actually be used to control it. Not exactly a smoking gun...
For now, the source of copper remains a mystery. The rest of the flock seems healthy, so we're hopeful that this ewe's copper levels were an anomaly. We'll definitely investigate any subsequent death losses - we're fortunate to have the CAHFS lab close by. And we'll continue to investigate the potential sources outlined above. Stay tuned.... And if you've had similar experiences with your sheep, please let us know!

Thursday, January 4, 2018

Grass, Water, and Warmth

Folks who don't raise grass (not that kind of grass!) and harvest it with grazing animals, I suppose, probably think we ranchers are always complaining.  We never have enough rain, except when we get too much. The rain doesn't come at the right time, or in the right place. The grass is washed out, or it matures too early. The summer heat shuts down our irrigated pasture growth, but we want warm soils in the fall to get the grass started. In other words, to the uninitiated, we ranchers are never happy!

Seeing ourselves through others' eyes, I think, is helpful. At a holiday party, a friend told me that her husband couldn't quite figure out why I was so worried about winter rain - and why I couldn't enjoy a "beautiful" sunny day in December. While I'm a worrier by nature, I think worrying about the weather is natural for anyone who relies on Mother Nature directly. That casual conversation planted the seed for this brief explanation of how our rangeland and pasture-based sheep operation works. I hope this is helpful!

Sheep (and cows, goats, deer, antelope, bison, elk, among other critters) are ruminants. At the risk of vastly oversimplifying their digestive systems, these animals have multi-compartment stomachs that contain bacteria that allow them to digest the cellulose contained in grasses and other plants (which we have difficulty digesting ourselves). These bacteria require protein to thrive - for a sheep to maintain weight and essential bodily functions, it's diet needs to contain at least 8 percent protein. The cheapest (and best, in my opinion) source of protein is green forage (grass, broadleaf plants, brush, etc.).

In our climate, the water "year" starts in October...
In our Mediterranean climate, most of our precipitation falls from November through March. If we get sufficient rain early enough in the fall (1 inch mid-October is ideal), the annual grasses and forbs (broadleaf plants like clover) on our rangelands will germinate and begin to grow. We typically move onto these rangelands in early December, by which time we hope there's enough green grass to meet the nutritional needs of our sheep. And we hope the rain keeps coming - while the grass goes dormant during the short, relatively cold days of December and January, we want to keep the soil moisture up so the grass will start growing again in February. In the best years, the annual grasses and forbs start growing in October and continue growing through the end of May. Since most of these plants on our unirrigated rangelands are annuals, however, they are compelled to complete their life cycles each spring - that is, even if it kept raining through the summer (or even with irrigation), our annual grasses and forbs would set seed and die. A note about irrigating our annual rangelands (because I’m frequently asked) - we simply cannot do it. We typically can't get water to much of these lands, and it would be too costly even if we could. These dead grasses are the iconic golden, rolling hills of our foothill rangelands. During the winter and spring months, these growing plants contain as much as 20-22 percent protein - more than enough for our sheep! As they mature and die, the protein levels crash - by August and September, these annual plants may be as low as 3-4 percent protein. Our sheep can graze this brown vegetation, but they need additional protein to allow their gut microbes to digest this more fibrous material.

In our operation, that's where irrigated pasture comes in! Unlike our annual rangelands, our irrigated pastures are planted with introduced perennial plants (like orchard grass, fescue, plantain, ladino clover, and birdsfoot trefoil - aren't these great names?!). To keep these improved pastures growing during the summer months, we must irrigate. And while rainfall is important to keeping these pastures alive in the winter and for resuming growth in the spring, we have to make it rain by watering these pastures every 7-10 days during the late spring, summer and fall.

We're fortunate in our part of the foothills to have a gravity-fed surface water system. In the simplest terms, this means we don't have to pump water to irrigate our pastures. We purchase water from the Nevada Irrigation District (NID), which has storage reservoirs ranging from Jackson Meadows in the high Sierra Nevada mountains to our east down to Scotts Flat Reservoir near Nevada City and Combie Lake between Auburn and Grass Valley. This system, partly a vestige of the Gold Rush, depends storing water both in these reservoirs and as snow - the higher elevation lakes, in particular, are snow-fed. In normal years, our irrigation water begins on April 15 and lasts through October 15. In particularly dry years, NID might delay deliveries in the spring or shut off the water earlier in the fall. Without irrigation to grow our late spring, summer and fall forage, we have to find other ways to supplement the protein in our flock's diet (usually with hay or a grain-based protein) - all of which adds to our costs of production.

Our management calendar is based on this system. Our ewes have their greatest demand for high quality forage in the last 3-4 weeks of their pregnancies and the first 6 weeks of nursing lambs. We match this 10 week peak in demand for high quality forage with the time of year when we typically grow lots of grass - late winter through spring, in our region. We try to match our system with what Mother Nature usually provides, but sometimes she doesn't live up to her side of the bargain. In the winter of 2013-2014, for example, we didn't have any rain for nearly 60 days in December and January. This meant less grass at lambing time (March), which in turn meant more labor on our part (moving sheep every 3 days rather than every 6-7 days). The winter of 2015-2016 was different - the rain in our part of the foothills was fine, but we had a much-diminished snowpack. Thankfully, NID was able to make normal irrigation deliveries - but another low snowfall year could have meant reduced irrigation water.
Here's how we try to match our production system with forage growth:
Ideally, supply (grass) should equal demand (sheep mouths)!

Every year, obviously is different - which is sometimes a source of frustration (and always a source of conversation) for ranchers. This year, our germinating rain came on October 20 (we measured 0.67 inches at home). It was another 3 weeks before we got another significant rain, but the second half of November was outstanding (we ended up with nearly 7.5 inches for the month). The grass on our annual rangelands was sufficient to feed our ewes when we turned them onto winter pastures on December 2. But then the rained almost stopped coming - we had just two storms (and less than an inch of rain) in all of December. And the first snow survey of the year yesterday indicated that the Sierra snowpack is just 24% of normal. As you might imagine, those of us who came through the 2012-2015 drought with grazing livestock are a bit spooked - many of us are dusting off our drought plans! For our operation, we do as much planning and preparation for drought as we can - we stock our pastures conservatively, we try to stockpile dry grass for the fall and winter, we keep careful records of our grazing and of forage growth. We also try to plan our responses if drought intensifies - setting dates for selling sheep if we don't have enough grass, for example.

From the outside, I can see where I might seem difficult to please. I want rain in October. I want it warm enough in the foothills in October and November to start our annual grasses, but cold enough in the high country that the snow pack builds. In the late winter and spring, I'd like sunny days mixed with periodic rain to extend the annual grassland growing season, but more snow in the mountains to fill our reservoirs. During the summer, I'd like warm days and cool nights that favor grass growth on our irrigated pastures. To further complicate the outside perspective on farmers and ranchers, the weather conditions that are favorable to our grazing operation might be harmful to a mandarin grower or vegetable farmer. Growing food is so darned complicated!

So if you happen into a coffee shop with pickups outside and farmers and ranchers inside, you can expect to hear them talking about the weather. If you're with a rancher when a weather forecaster talks about another beautiful, sunny day in December, you can expect him (or her) to gripe! And don't be surprised if he (or she) checks multiple weather apps to find a more hopeful forecast!
Almost perfect - lots of lambs, and lots of grass in front of them!