PARTNER FEATURE ▶▶▶
How dietary fibre can tackle heat stress in sows
Heat stress is not only of interest for swine producers in countries with tropical or sub-tropical areas. Even in temperate latitudes, at least for a few weeks per year, sub-optimal climatic conditions occur. How can sows be better prepared for the heat?
BY STEFAN HIRTENLEHNER AND CHRISTINE POTTHAST, AGROMED, AUSTRIA W
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100 Source: Adapted from Xin and Harmon, 1998.
hen talking about heat stress, it is important to realise that it is not only the temperature that affects humans or animals; it is a function of ambient temperature and relative humidi-
ty. Figure 1 demonstrates that the risk of pigs suffering from heat stress rises even at a moderate temperature of 24°C when the relative humidity is 75%. In 2017, researchers Mat- thew C. Lucy and Timothy J. Safranski of the University of Mis- souri, USA, gave a range of thermoneutral conditions for pigs in the temperature range of approximately 15–22°C with 60–70% relative humidity.
Figure 1 - Temperature-humidity index for pigs. Ambient air temperature in °C
21 22 23 24 25 26 27 28 29 30 31 32 33 No heat stress
Exact values for the increased risk of suffering from heat stress are species-specific due to differences in biological functions between livestock animals. Sows have only limited ability to cool down their body temperature by evaporation due to the lack of sweat glands in swine skin and will increase respiratory frequency.
Heat stress alert
First obvious signs of heat stress Nevertheless, the first obvious signs of heat stress are quite similar across different species of livestock animals – they change their behaviour to get rid of excessive body tempera- ture, to cool down via an enlarged body surface and to avoid as many heat-producing activities as possible: heat-stressed sows reduce their locomotion and lie (usually stretched out) in the coolest area of their barn, they restrict their feed intake and at the same time they increase their water consumption. Reduced feed intake will have severe consequences, visible in diminished body condition of sows as well as reduced fertili- ty (prolonged inter-oestrus intervals), smaller litter sizes and reduced weight of newborn piglets. In addition to losses due to those performance reductions, the sow’s health is im- paired. Farms’ rentability is further cut by increased medica- tion costs to address the rise in inflammation as well as by increased mortality. For 2003, the total economic loss through impaired prodution due to heat stress was estimated at up to US$ 2.4 billion across all livestock species, including losses of US$ 299– 316 million for the US swine industry alone.
22 ▶PIG PROGRESS | Volume 36, No. 7, 2020
PHOTO: SHUTTERSTOCK
Relative humidity in %
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