Changes in the breeding of pigs over the last 20 years has led to the size of litters increasing by on average two piglets. This increase has resulted in piglets with a lower birth weight, which in turn can lead to an increase in piglet mortality. This poses a challenge to both animal welfare and to profitability.
5 -- 10% of all piglets are registered as stillbirths and a further 10 -- 20% die before weaning when at five weeks old. It is essential to know more about the causes of these stillbirths and piglet losses if we are to find preventive measures. The increase in litter size and a long birthing process are both factors that increase the risk of stillbirth and necessitate more supervision during the birth and the piglets' first weeks of life, if losses are to be avoided.
Vibeke Rootwelt's doctoral thesis indicates that a torn umbilical cord is a major cause of stillbirth and that the surface area of the fetal membrane and the birth weight of the piglets make a significant difference to their chances of survival during the weeks leading up to weaning. Rootwelt has shown that variations in breed affect the survival rate and that the breed Duroc appears to produce fewer stillbirths and more robust piglets with a higher birth weight. For this reason, her research has resulted in this breed becoming more prevalent in pig farming in Norway.
Rootwelt's thesis also suggests that more focus should be given to an optimum, rather than a maximum, litter size and that improved animal welfare and profitability, combined with a lower intervention rate during the first weeks of life should be given priority. However, more research is necessary in order to ascertain the optimum size of litters in relation to the capacity of the sow.
Veterinary surgeon Vibeke Rootwelt defended her doctoral thesis on 14th December 2012 at the Norwegian School of Veterinary Science with a thesis entitled: "Piglet stillbirth and neonatal death."
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