So how much colostrum should the lamb receive? From a large number of studies at Lyons, we have a target of 50ml colostrum per kilo of lamb bodyweight at 4-5 times in the first 24 hours of life, or around one litre in the first day for a 5kg lamb. Getting colostrum in as early as possible is key.
Obviously, it's not possible to measure colostrum on-farm so the easiest way to ensure adequate intake is to have the ewe producing plenty of colostrum and observing the lamb to make sure he can suckle. This can be assisted by removing the wax seal in the teat, individually penning ewes after lambing, and stomach tubing any lambs which are not suckling. Some farmers will tube all lambs once they're born and this will give those lambs an extra boost.
Hypothermia is a big killer of lambs on farms and is directly linked to poor colostrum intake.
When a lamb is suffering from hypothermia, its body temperature will drop below the normal temperature of 39°C. Between 37-39°C, we refer to the lamb as being moderately hypothermic, which is quite easy to correct. Below 37°C, the lamb is said to be severely hypothermic and is more difficult to treat. So, the earlier you can act the better the outcome.
Treatment of the moderately hypothermic lamb includes drying it if it is wet, feeding colostrum by stomach tube and moving the ewe and lamb to a sheltered environment. The use of artificial heat and separation of the lamb from its mother is usually unnecessary, and if done may upset the ewe and lamb bond.
In addition to a decline in body temperature, if a lamb becomes severely hypothermic it also becomes deficient in glucose if it is more than five hours old. Warming up a lamb from this state does little to reduce the risk of death, in this case from glucose deficiency in the brain.
Firstly, the glucose deficiency needs to be corrected by the administration of an intraperitoneal glucose injection. This involves the injection of a 20pc warm glucose solution into the abdomen of the lamb at a rate of 10ml/kg lamb birth weight. The injection site should be around 1cm to the side of the navel and 2cm behind the line of the navel. When holding the lamb by the front legs, the injection should be administered at a 45° angle, almost aiming for the tail head of the lamb. A 19-gauge, 1-inch needle is used.
Then you can warm the lamb with artificial heat. A red lamp is often the best option as it can allow the lamb to remain with the ewe, thus preserving the bond.
The second function of colostrum is to give the lamb protection against disease.
When the lamb is born, it doesn't have any immunity to the diseases it comes in contact with immediately after birth and is dependent on absorbing antibodies (immunolgobulins) from the ewe's colostrum. Therefore, it's crucial that the lamb gets a good feed of colostrum before the lamb is one hour of age.
From the moment the lamb is born, it begins to lose its ability to absorb these immunoglobulins and the mechanism completely shuts down 24-48 hours after birth.
This is an important aspect to realise as every year we hear of indoor lambing ewes having very little milk until they are let out to grass. But it takes 2-3 days for the milk to come when a ewe is let out to graze. While this is welcome from a nutritional point of view, the lamb is incapable of absorbing any worthwhile amount of antibodies at this stage and remains wide open to many diseases.
Most lambs will stand and suckle quickly, but all is not lost if they don't, as the lamb's ability to absorb immunoglobulins remains reasonably high for the first 6-8 hours. It's the ability to suckle that is key to the lamb's ability to produce heat in the hours immediately after birth.
Roughly 20-25pc of the immunoglobulins consumed by the lamb will be absorbed into the bloodstream. Our research at Lyons has shown that absorption will increase as immunoglobulin intake increases up to a maximum of 15g/kg lamb birth weight during the first 18 hours of life.
The colostrum produced immediately after birth contains about 20pc protein, half of which is in the form of immunoglobulin. At 10 hours after lambing, this will have reduced by a third, and by 18 hours after lambing, it will have reduced further to just 3pc of colostrum. So, in practice, one litre of colostrum produced by a ewe in the first hour after giving birth will have the same amount of protective immunoglobulins as three litres produces 18 hours later.
Mineral supplementation of the pregnant ewe is widespread and generally seen as beneficial to the lambing outcome.
However, care needs to be taken in supplementing iodine to the pregnant ewe. The ewe requires around 1mg of iodine per day in late pregnancy, but recent work at Lyons has shown that, when given the opportunity, ewes will consume considerably more iodine than they require. This can lead to serious problems in terms of immunoglobulin absorption in the lamb. The progeny of ewes fed excessive iodine in late pregnancy are unable to absorb immunoglobulins.
These lambs are pre-programmed in the uterus and, regardless of what happens after birth, their ability to absorb the antibodies is greatly reduced. As the magnitude of excess iodine increases, so does the severity of the response.
Ultimately, this results in the production of lambs with a greater risk of contracting disease in early life.
Fortunately, it is only the final two weeks of pregnancy that are critical. If there is a fear that iodine intake is well above requirements, withdrawing the excess for the final two weeks should minimise any problem relating to reduced ability of the lamb to absorb antibodies.
Dr Tommy Boland is a lecturer in sheep production at Lyons Research Farm, UCD. Email: firstname.lastname@example.org