February 2015: It’s cold, but how much does it cost?

The UK’s average winter temperature is 3.7C, and this makes environmental control in pig buildings difficult and expensive.

All animals function at their best under thermo-neutral conditions, where the body is not attempting to create heat to keep warm, nor get rid of excess heat to cool down. Outside of this window, they’re doing one or the other trying to reach thermo-neutrality, and this creates degrees of inefficiency.

Pigs, like humans and other mammals, are known as endotherms. This means that they regulate their body to create thermo-neutrality by chemical reactions as part of metabolic function. It’s generally the metabolism of fats and sugars that release the necessary heat. Interestingly, in the resting human body, the brain provides about 16% of the total heat produced – so in cold weather, wear a hat!

Physical size and the ratio of surface area to volume has a huge impact on creating a thermo-neutral environment, whether that be a mouse or an elephant. So, when it comes to pigs, the piglet has a larger surface area to volume ratio than the sow and it can therefore lose more heat – more of its diet will be used to keep warm than to grow, and this is inefficient. Added to this, a cold piglet is more likely to get sick.

It’s from this fact that we get the idea of a lower critical temperature or LCT. This is the point at which energy is used for heat production rather than for normal metabolic function.

It’s worth checking that your buildings are warm enough and running at the correct temperature in these winter months. And from a husbandry perspective, the temperature isn’t the only variable or mechanism that will affect heat loss in the young pig, ventilation pattern and speed, feed intake, group size, bedding and flooring all have major influences on the LCT of animals in any situation.

A guide for the suggested temperature for a 10kg pig can, therefore, range between 20-24C when housed in straw and up to 25-28C on slats. The welfare codes don’t offer suggestions dependant on environmental conditions, and give a large range of guideline temperatures. Interpreting these suggestions, a later-weaned pig of about five weeks of age should be kept between 22-27C, largely falling between the two previous extremes cited.

Research has suggested that growing/finishing pigs can lose between 10g and 12g of daily liveweight gain for every degree less than the LCT. Extrapolating this further could easily mean that pigs kept in conditions up to 5C less than the LCT will take two weeks longer to finish.

If we then suggest that 40% of the feed consumed is going on maintenance requirement, and that pigs are eating 3kg/day in these last two weeks, this could easily mean an additional 17kg feed/pig costing about £3.60/head.

So, it pays to keep warm!

> Dr Phil Baynes has spent his career in pig welfare and nutrition. Based in Cheshire, he runs Baynes Nutrition and is a consultant nutritionist to Provimi

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