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Thin Sow Syndrome

(293) The thin sow syndrome occurs over a period of months, with gradual declining body condition until 10 to 30% of the animals have a condition score between 1 and 2. The syndrome arises due to inadequate nutrition or poor quality feeds failing to satisfy the bodily needs of the sow in that environment. During lactation the sow is unable to maintain her body condition due to either an insufficient intake of energy, or increasing demands due to low temperatures or high milk output. The sow therefore uses her body fat to maintain the supply of energy and once this is used muscle protein is degraded. This process continues over successive lactations. It is exacerbated in sows kept outdoors in cold weather and by heavy worm burdens. In sows kept permanently outdoors the stockman should ensure that all the sows have a high body score before the start of cold weather.

Clinical signs

These will be evident by the appearance of a number of very thin sows. Each week during the clinical observations of the herd, an assessment of the overall body condition of sows in the dry sow area should be carried out. If there are more than 5% of sows scoring body condition less than 2 then the herd might be moving into problems. In such cases a more specific examination should be made of body condition at farrowing and at weaning time, the feed intake during lactation and pregnancy, the quality of the feed itself and evidence of any specific diseases.


  • This should be aimed at increasing the nutritional intake of the sow during the various key periods of production and attending to any disease situations.
  • Immediately raise feed intake across the whole herd by 1 to 2kg a day for a period of 10 to 14 days.
  • Sows that have become very thin should if possible be moved from their dry sow accommodation and housed in warm deep straw pens in an environmental temperature of at least 20ºC (70ºF) and ad lib fed for 3 to 4 weeks using a lactating diet because the appetite in such animals is often depressed. It is essential to do this to reverse the catabolic or negative energy state and allow the sow to lay down body fat again. If the sow has become too lean (body score 1) the condition can become irreversible.
Management control and prevention
  • Check the feed used per sow per year. This should be a minimum of 1.1 tonnes per annum for an indoor herd and for an outdoor herd 1.4 tonnes per annum.
  • Check the quality and energy content of the ration in relation to the feed intake.
  • Check the energy content of the ration during lactation. For the lean genotype this should be at least 14.2MJ DE/kg of feed and 1.1% lysine.
  • Sows should be fed at least twice daily to appetite during lactation commencing three days post farrowing.
  • Assess the body condition of sows coming into farrow and at weaning time.
  • Monitor temperatures in the dry sow accommodation. For indoor sows in stalls or tethers with no bedding it should not drop below 17ºC (63ºF), preferably higher and should not vary greatly day and night, otherwise it will be necessary to increase feed intake to compensate.
  • Select at least twelve faeces samples from thin sows. Submit them to a laboratory for examination to eliminate coccidiosis, blood (from gastric ulcers) and parasites.
  • Always carry out an immediate investigation if the body condition of sows is dropping because if it is not corrected there will be infertility, poor litter sizes, increased disease and mortality.
  • Assess the comfort of sows last thing at night or first thing in the morning, particularly during severe spells of cold weather. Always increase feed intake when external temperatures drop significantly.
  • Damp floors or draughts will increase the energy requirement of the dry sow. Once the body condition of the sow has dropped then it becomes more susceptible to a variety of diseases, including gastric ulceration, cystitis and pyelonephritis, PRRS and other respiratory viruses.

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