Twin lamb disease risk in cold snap
THE recent cold weather could predispose more ewes to pregnancy toxaemia (twin lamb disease), says John Twigge, technical and marketing manager with Frank Wright Trouw Nutrition International.
”Pregnancy toxaemia is the result of a dramatic shortfall in dietary energy intakes in the six weeks immediately before lambing,” he says.
“For many sheep, this time has coincided with the current cold spell when feed supplies may have been reduced, while the animal’s energy demands will have increased due to a higher maintenance requirement.”
Mr Twigge warns the risk of pregnancy toxaemia can also have been increased if ewes were transported, or if the diet was changed too quickly as farmers reacted to the cold weather.
During the last six weeks of gestation, the ewe faces extreme demands for energy, as 70 per cent of lamb growth takes place at this time. The problem is made worse as intake is suppressed due to the developing foetus reducing rumen volume.
Inadequate intakes of fermentable carbohydrates starve the liver of propionate and lead to a decline in maternal blood glucose levels, says Mr Twigge. If these levels fall below the level required for brain function, then twin lamb disease will develop.
“The disease can affect any age or breed of ewe but over-fat or over-thin ewes and those carrying multiple lambs are most at risk,” he says.
“Symptoms include ewes isolating themselves, a thick yellow discharge from the nose, drowsiness, the head pulled back and to side, and muscle tremors. In addition, ewes often ‘star gaze’.”
Mr Twigge advises sheep farmers to be watchful for the signs of the disease but, more importantly, to continually monitor body condition, as this can be an earlier indicator of problems.
“Pregnant ewes should not lose excess condition and losses in condition score of more than 0.5 will lead to problems,” he says.
“If possible, ewes should be scanned and grouped accordingly, based on the number of lambs and condition.
“Ewes carrying multiple lambs and those in poor condition can be fed a diet with a higher nutrient density.”
Gradual feed increase
The aim should be to feed a nutrient-dense, high dry matter diet based on quality forages and concentrates. Feed should be increased gradually during the last six weeks of pregnancy. A 60kg twin-bearing ewe at lambing requires the ration to contain 12.9MJ per kg DM to meet her daily energy requirement.
Unless this energy demand is very carefully met, excessive back fat is mobilised to meet demands, the liver becomes overworked which has the effect of depressing appetite further, exacerbating energy deficit.
Mr Twigge recommends feeding twin- and triplet-bearing ewes, and those in poor condition, a glucose supplement on a self-help basis, to allow ewes to regulate their intake.
Feeding high glucose buckets supplies a concentrated source of readily fermentable energy, which helps to maintain circulating blood glucose levels. As the buckets are licked rather than chewed or bitten, they provide a continual trickle-feed of nutrients which stimulate rumen fermentation and digestion and can improve fibre utilisation.
“By acting promptly, group ewes according to condition and ensuring sufficient energy in the diet, farmers can reduce the risk,” says Mr Twigge.