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INTERVIEW ▶▶▶ Prof Bruno Silva


A tropical view on heat stress in sows


Heat stress in pigs can vary strongly depending on the region where the animals are being kept. As a tropical climate is part of his daily life, Prof Bruno Silva of the Federal University of Minas Gerais, Brazil, has made ‘heat stress in sows’ his specialism.


BY VINCENT TER BEEK, EDITOR, PIG PROGRESS ‘H


eat stress’ is a topic that has been getting in- creasing amounts of attention – if not for the growing swine business in tropical countries, then because of the climate change. Still, only a


limited amount of research institutes and universities around the globe have teams focusing on the impact of heat stress on swine production. The Federal University of Minas Gerais, Brazil, is one of them, and probably one of the few actually located inside a tropical zone. In fact, Brazil is home to various tropical climates, hence different types of heat stress occur depending on the location in the coun- try, varying from 26ºC to a whopping 40ºC. The majority of the pig population is concentrated in the south east and south region of Brazil. There, pigs often suffer because of the extreme variation in temperature, especially during the summer – from hot and humid during the day, to very cold during the night. Prof Bruno Silva, attached to the university, has been specialising in the topics of swine nutrition and environmental adaptation since he joined the university in 2012. Particularly for lactating sows he knows like no other what heat stress can do – and finding solutions to that is what keeps him going.


Pig Progress: Is there enough attention for sows in relation to heat stress? Prof Bruno Silva: “I always ask this to farmers and students: what is more important to you, the product or the factory? In 90% of the cases they are focused only on the product, which are the piglets. They forget that if the factory is not working properly, they can’t deliver a good product. So we really have to focus on the sow to get the best out of the animal, to express its potential for piglets too.”


14 ▶ PIG PROGRESS | Volume 34, No. 5, 2018


Are you on your own with that opinion in Brazil? “I think things are changing. People are aware that we have to do something. One of the main problems related to pigs is that the animal tolerates mistakes. One can commit mistakes with the pig and it will still go on producing. Below its potential, but producing. It’s not punishing producers that much.”


Like poultry? “Yes. If one makes a mistake with poultry, they drop dead. But sows, well you’ll get a 10% mortality, but they are still producing.”


How much is there to be gained, if everything is correct for the sow? “If we are talking about basic improvements, in my experience, 23-25% in terms of sow output. So we are talking about sows that would produce piglets around 1 kg or 1.2 kg heavier at 23 days of age.”


What is typical for heat stress in southern Brazil? “Sometimes you have to deal with two climates in the same day; during the day it is hot and during the night it is cool. Thermal vari- ation or amplitude is what takes its toll on animals; it is much more aggressive to the animal than a constant heat stress, both physio- logically and metabolically. To a constant heat stress, an animal can adapt and it will keep producing at a lower level. But in situations with thermal variation, this is much more complicated, leading to higher mortalities in sows.”


How do sows normally lose their heat? “Basically they are dependent on so-called ‘sensitive heat loss’, i.e. conduction, radiation or convection. The most effective one is by conduction – so if the pig enters in contact with a surface that has


PHOTO: BRUNO SILVA


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