The aims of this study were, firstly, to evaluate the effects of climatic variables on daily feed intake of lactating sows and, second, to establish whether the response of sows to variation in temperature on feed intake during lactation was heritable, explain Rob Bergesma of Institute for Pig Genetics (IPG) in the Netherlands and Susanne Hermesch of the Animal Genetics and Breeding Unit (AGBU) at the University of New England in Australia.

In a paper published in Journal of Animal Science, they report that a total of 82,614 records for daily feed intake during lactation were available for 848 sows with 3,369 litters farrowing from January 2000 to December 2007. Climatic parameters available from the nearest weather station were maximum 24 hour outside temperature, day length changes and humidity.

Although ambient room temperature was modified at the animal level in the farrowing shed, these climatic variables still had a significant effect on feed intake during lactation. Regression coefficients temperature and humidity were 0.01385±0.00300 (temperature); 0.00031±0.00009 (temperature2) and 0.01443±0.00620 (humidity); 0.00009±0.00004 (humidity2).

There was an interaction between temperature and humidity, partly due to the climate control in the farrowing shed. At low temperature, feed intake increased considerably with greater humidity, in contrast to a small reduction in feed intake with greater humidity at high temperature.

Day length change was modelled with a cosine function. At the start of autumn (on 21 September), sows ate 0.36±0.056kg per day less feed than at the start of spring (on 21 March).

Daily feed intake during lactation was described as a function of days in lactation and as a function of both days in lactation and temperature using random regression models.

The average heritability and repeatability summarised over the day in lactation at the mean temperature were 0.21 and 0.69, respectively. Genetic variance of temperature response on feed intake was less than 20 per cent of the day effect. The permanent environmental variance was two-fold (day) and four-fold (temperature) greater than the corresponding additive genetic variance.

Heritabilities of daily feed intake were greater during the first week of lactation than in the rest of lactation. The genetic correlation between days decreased as time increased down to about 0.2 between the first and last day in lactation. The genetic correlation between feed intake records at the extreme temperatures decreased to about -0.35.

Bergesma and Hermesch concluded that random regression models are useful for research and results may be used to develop simpler models that can be implemented in practical breeding programmes.

They found an effect of temperature on lactation feed intake, even in this climate-controlled environment located in a temperate climate zone. Larger effects are expected in more extreme climatic conditions with less temperature-controlled farrowing sheds, the researchers added.

Reference

Bergsma R., and S. Hermesch. 2012. Exploring breeding opportunities for reduced thermal sensitivity of feed intake in the lactating sow. Journal of Animal Science, 90(1):85-98. Published online before print on 25 July 2011, doi: 10.2527/jas.2011-4021.

Further Reading

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January 2012