Farm Ireland
Independent.ie

Sunday 24 September 2017

Minimise lamb mortality by improving management strategies

Lamb mortality rates are as low as 5pc in well managed flock, but can hit 20pc where serious animal issues prevail

Minimise lamb mortality by improving management strategies
Minimise lamb mortality by improving management strategies

Tommy Boland tboland@ independent.ie

Lambing season is perhaps the most important stage of the production cycle on a sheep farm.

It is also an extremely high risk period in terms of both ewe and lamb mortality. The ewe is susceptible to health issues with twin lamb disease, prolapse, milk fever and acidosis among the most common issues arising.

The lamb itself is obviously extremely vulnerable immediately after birth.

It is exposed to a very hostile environment relative to the comforts it enjoyed in utero. The dangers of disease, hunger, hypothermia, predation and mis-adventure are very real.

In fact around one of every two lambs which die on sheep farms will do so in the first 48 hours of life. While it just about impossible to completely remove these challenges,l they can be greatly minimised through appropriate nutritional and lambing management.

Lamb mortality around lambing time can be as low as 5pc on a well-managed flock, with figures in excess of 20pc unfortunately also reported. To minimise lamb mortality we need to focus on what are the main requirements of the lamb after birth.

Hypothermia

The biggest challenge is hypothermia and simply housing your ewes at lambing time does not remove this risk factor.

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When the lamb is born it is extremely susceptible to hypothermia. Nature has designed a set of tools to minimise lamb loss from this cause.

Firstly the licking and grooming of the lamb by the mother will dry the lamb and encourage it to stand and begin seeking out the udder. Wet lambs (either lambed outdoors in wet conditions or un-groomed by their mother) are five to eight times more likely to suffer from hypothermia than a dry lamb.

Secondly the lamb contains a very specific energy store called brown adipose tissue or BAT. This BAT is the first source of energy for the new-born lamb, which is utilised to provide heat. If the mother is well fed this BAT tissue will be relatively abundant.

However, this is only part of the story. The ewe must also receive adequate selenium and iodine levels in late pregnancy, otherwise the lamb will not be able to make the most of this BAT to produce energy.

Colostrum consumption is most important of all to ensure the lamb does not suffer from hypothermia. Almost immediately after birth the lamb will require 50ml of colostrum per kg of body weight. During the first 24 hours of life, each lamb requires 200ml of colostrum per kg body weight.

If the lamb is born and maintained outdoors in windy wet conditions this figure required in the first 24 hours of life increases to 280ml of colostrum per kg of body weight.

If supplementing a healthy lamb in the first 24 hours of life, there should be no concern with administering 50ml per kg of body weight in a single feed.

This practice is carried out at Lyons annually with no adverse effects. Colostrum should be collected as hygienically as possible and fed at body temperature.

For sick/weak lambs a little and often approach should be taken, with 50ml administered in a single feed and repeated frequently (2-3 hours) until the lamb is showing signs of recovery.

When stomach tubing any lamb excess pressure should never be applied to the plunger in the syringe attached to the stomach tube. Not only will this cause discomfort to the lamb it can result in colostrum coming back up the oesophagus and entering the lungs.

The second main source of lamb mortality in early life is disease, with the two main culprits being joint-ill and E-coli (watery mouth or rattle belly). In both instances hygiene and colostrum intake are of vital importance.

Resistance

When the lamb is born it is completely susceptible to all diseases in its environment. In order to gain resistance to these diseases, transfer of antibodies (compounds which fight disease) from colostrum is essential.

In terms of colostrum, once lambs are receiving the levels outlined above to stave off hypothermia they should also receive sufficient antibodies to help fight disease.

The transfer of antibodies from the colostrum to the lamb is dependent on selenium and iodine levels in the ewe's diet.

If the ewe receives too little selenium or too much iodine then the lambs' ability to capture the antibodies from the colostrum is reduced making that lamb more likely to suffer from disease.

Selenium requirements in the diet of the ewe during late pregnancy are 0.1 to 0.5mg per ewe per day. Iodine requirements are approximately 0.7mg per ewe per da, increasing to 2mg per ewe per day if ewes graze brassica crops that contain goitrogens.

When feeding colostrum to lambs obviously ewe colostrum is the best option. Where this is not available (mastitis, ewe death, low volume, multiple lambs etc) an alternative source is required. Both artificial colostrum replacers and cows colostrum are viable options.

The artificial colostrum replacer will not contain all necessary antibodies, but will contain many other nutrients required by the new born lamb' With cow colostrum, feeding levels need to be increased by 30pc to compensate for the lower nutrient content of cow colostrum as compared to sheep colostrum.

The use of cow colostrum also runs the risk of anaemia in the lamb, but this risk is modest in most cases and is further reduced by mixing colostrum form a number of cows.

Vaccination of cows with the sheep clostridia vaccine has been practiced in the past to increase the specific antibody content of the colostrum, making it more suitable to the lamb.

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