I should begin this account by saying that it might seem a little gruesome to some. I don't write it for its shock value, and I don't write it to seek sympathy. Rather, I wanted to document the events that led to our first orphan lamb in nearly 25 years of raising sheep - mostly for my own use, but also in the hope that it might be instructive to others.
This year's lambing season has been remarkable for the number of big lambs and assisted births we've had - so remarkable, in fact, that my partner, Roger Ingram, has been reviewing scientific literature about lamb birth weights. He has found several publications that seem to shed light on our experience. In addition to normal variation, lamb birth weights vary based on litter size (singles are typically larger than twins), number of lambs the ewe has had (maiden ewes generally have smaller lambs, while "middle-aged" ewes have larger offspring; older ewes seem to again have smaller lambs), and the sex of the lamb (ram lambs are larger than ewe lambs). Not surprisingly, however, environmental factors play a role in birth weights as well. Some of the research Roger found indicated that body condition prior to breeding is a factor. Climatic conditions during the first 50 days of a ewe's pregnancy can impact birth weight (warm weather seems to be related to heavier lambs), as can forage quality and quantity in the last 50 days of gestation (when 70 percent of fetal development occurs).
Setting aside the sheep-related variables listed above, we examined the nutritional and climatic conditions this year for some clue regarding our big lambs.
First, our flushing program (when we provide additional high quality feed to the ewes prior to breeding in increase ovulation and thus twinning) was extremely effective this year. In late August, the ewes had an average body condition score (BCS) of just over 3 (on a scale of 1 to 5, with 1 being thin and 5 being obese). Just four weeks later, the combination of irrigated pasture and canola meal we'd fed the ewes increased their average BCS by 10 percent!
Second, following our germinating rain in mid October, we had a warm and wet autumn. November was notably warm in Auburn - I'd need to look at my weather journal, but I remember remarking about how mild the weather was. We turned the rams in with the ewes on September 29 - and most of the ewes were bred by the end of October. The first 30 days of their gestation were marked by relatively warm weather.
The warm, wet fall resulted in incredible forage growth on our annual grasslands. Roger says this was the best winter grass year he's seen in 30 years - and I'd concur with that assessment. Quantitatively, range monitoring at the Sierra Foothill Research and Extension Center 20 miles north of us in Browns Valley backs this up - they measured 185 percent of normal forage production on January 1, 2017. In other words, we had almost twice as much high quality grass in January and early February as we typically have.
Based on Roger's literature review, we seem to have been in the "perfect storm" in terms of lamb birth weights this year. And our experience once lambing started supports this assertion. We've assisted in far more deliveries than normal, and we've had more malpresented lambs than normal (a malpresented lamb may have a leg or its head back, or be presented backwards). Fortunately, through Monday, we'd only lost one lamb due to these problems.
Last week, we noticed that one of our ewes had a mild vaginal prolapse. We've seen this happen before - and as with our past experience, her prolapse would disappear once she stood up and moved around. We decided to simply keep an eye on her - our previous experience suggested that this was the right course of action.
On Monday morning, during the coldest storm we've had during lambing in several years, I arrived at the pasture to find the ewe in labor and straining. The prolapse had reappeared, and at my wife's suggestion (I should note that my wife Sami is also our vet), I pushed the prolapse back into place. The ewe remained standing, and my repair seemed to hold. She seemed more comfortable. I returned to trying to get several sets of chilled lambs on their feet.
About an hour later, I found the ewe straining again - and the prolapse was back out. I again pushed it back - and again it seemed to hold - but not for long. About 30 minutes after this second repair, I discovered that she'd perforated her rectum and had disemboweled herself. It looked even more gruesome than it sounds. At that point, I realized there was nothing we could do to save her. Fortunately, Sami was able to get to the pasture about 30 minutes later - and our focus turned to trying to save the lambs while alleviating the suffering the ewe. Sami sedated her and performed a c-section. The first lamb she delivered was huge - I estimate it was at least 15 pounds (out of a ewe that weighed maybe 160 pounds). I suctioned the mucous from the lamb's nose and mouth and rubbed it vigorously with a towel. Despite taking a few feeble gasps, the lamb's heart never beat. The second lamb was just as big - and very definitely alive. Roger cleaned it off, and it was trying to stand within 5 minutes of entering the world. It's home with the other bottle lambs and doing great.
Sami then euthanized the ewe. She's the first ewe we've ever lost during lambing. Sami remarked that the lambs were obviously full term but seemed to be too large to get into the birthing position (normal position is for a lamb to emerge through the birth canal with its nose tucked between its front legs).
Based on what Roger learned in his literature review, I'm not surprised that we are seeing bigger lambs this year. Management-wise, I'm not sure there is anything we could do differently. We may adjust our flushing procedure slightly (perhaps we'll use a feed that's not quite as high in protein and energy as canola meal). The weather and forage conditions are out of our control. Knowing that a warm autumn and doubled forage production in January might be an issue will help us prepare for the added labor requirement at lambing in future years.
For more on the subject, here's a link to Roger's latest Foothill Rancher newsletter!