More is not better if lamb mortality increases with higher birth rates, says Saskatchewan veterinarian
As fertility rates rise for lambs and kids, so does the need for better management practices in keeping them alive.
However, therein lie the issues, said Dr. Fritz Schumann of the University of Saskatchewan’s Western College of Veterinary Medicine.
“Even if fertility rates are high, there must be a point where physiologically the lambs can’t survive if there are too many of them,” the veterinarian said during the recent Healthy Sheep and Goat Workshop in Saskatoon.
“I think there must be physiologically an end to where we can’t have too many lambs per ewe, except if you take them away right at birth and then that involves a lot of nursing care and a lot of feeding and management to get them over the first couple of days.”
Some in the industry are asking whether encouraging more lambs per ewe is justified, but Schumann said opinions vary widely.
“Personally, I think if we have lamb mortality rates of 20 or 25 percent, and we do our best in keeping them alive and we get too many lambs born per ewe, I think yes, we went too far because it doesn’t help us much,” he said.
“If you have 25 percent mortality rate where our aim is five and 10 percent, then it’s better to have less lambs per ewe and keep them alive than having five lambs, which are all weak and struggling to stay alive.”
Schumann said the solution for increasing the fecundity of sheep and goats is the producer’s ability and determination to micro-manage the operation during birthing season.
“I think producers need to realize that lambing sheep or kidding goats, that it’s a major management issue, which has little to do with vaccines and antibiotics. It has a lot to do with passion for the sheep and to raise them proper,” he said.
“It’s the desire of the producer to keep the lambs alive, and management is probably the major, major component of that.
“For that reason, I personally think having two or three lambs per ewe is better than having five lambs per ewe.… I would think 160 to 180 percent would be good.”
The most common causes of lamb losses are:
- abortions, stillbirths: 45 percent
- infectious diseases :14 percent
- accidents,predation : 13 percent
- hypothermia, starvation: 12 percent
- dystocia: seven percent.
- genetic defects, misc: 10 percent
Schumann said many producers continue to underestimate the amount of colostrum that newborn lambs need.
“It’s the same in beef cattle. Farmers need to know, the more colostrum the better, and that’s what keeps them alive,” he said.
“The lambs, especially, because they have a big surface area (to body mass), they need to produce a lot of heat and the only way they produce a lot of heat is by getting enough colostrum.”
The health of the ewe is also critical during gestation because that affects how much reserve the lambs can store as brown fat in their system. Lambs are also born fat to produce heat and is a factor in warding off hypothermia.
“You think it’s warm for them, but they come from a 39 degree uterus out into an environment, even if it’s plus 10 and the wind is 15 km-h, it’s very cold for them,” he said.
“They will lose so much heat that in half an hour they won’t get up to suck colostrum…. The management needs to increase drastically to make the lambs survive.”
Bigger isn’t necessarily better, and producers should aim for an average birth weight.
“The ideal birth weight should be three to six kilos because if they are lower than that they die more and if they’re bigger than that you end up with a high mortality because you have a lot of dystocia problems,” he said.
Newborn lambs must overcome three major factors to survive: nutrition, temperature regulation and infectious disease.
Schumann thinks ewe nutrition is the most important, and body scoring needs to be done on a regular basis.
“You need to segregate the skinny ones from the other ones and then to watch the end of gestation,” he said. “You need to realize that they just can’t live off of hay. They need to eat volume wise; too much and there’s not enough space in the belly because the lambs take up more space then the rumen takes up. They need more energy dense rations (such as grain) so they can keep up with their energy.”
He said the fetus grows 70 percent during the last third of pregnancy, which results in less space in the ewe’s rumen as the womb increases.
Having adequate room for the ewes to move around also becomes more important, especially if they are fed grain.
“They all need to be able to eat at the same time. If you have too little bunk space, then the big strong ones get fatter and fatter and the less dominant ones get less and less feed. It doesn’t solve the problem,” he said.
“It’s all an integrated system, but I think people need to realize that nutrition of the ewe and body condition scoring, which we always talk about, is an easy thing to apply.
“It’s a hands-on thing and it takes time to do and you need to make decisions and trying to rule out other factors which cause them to lose body condition.”