Thermoregulation is the process that enables maintenance of a relatively constant body temperature, balancing the mechanisms of heat production and heat loss. Pigs are homothermous animals which mean they regulate their own body temperature.

Heat stress occurs when the animal is unable to regulate body temperature effectively during hot and humid days. This leads to a variety of problems that influence the performance and health of pigs.

As a pig gets older, it’s ideal temperature declines. Thus, heat stress is a greater concern in older, finishing pigs (>50kg), sows and boars than in younger pigs. Heat stress begins to affect sows, boars and finishing pigs at about 21° C. If temperatures remain above 28° C for more than 2-4 days, decreases in performance and reproductive efficiency can occur if cooling relief isn’t available.

Heat stress index for swine

Heat loss mechanisms at 24° C

Heat loss mechanism at 34° C

Clinical symptoms of heat stress

A pig regulates its temperature through panting and through cooling its skin. Panting increases airflow and evaporation of water from the lungs, which releases heat.

1. Comfortable temperature signs

• Normal behaviour
• Normal physical activity
• Normal feed intake
• Core temperature maintained stable
• Breathing frequency 20-30/min

2. Heat-stressed signs

• Lethargic
• Laying of floor
• Decreased food intake
• Core temperature increasing
• Breathing rate increases (30-40/min)

3. Above critical temperature signs

• Fatal physiological state
• No water and food intake
• Sharp increase in core body temperature (43˚C)
• Increased breathing rate (180/min)

Effects on reproductive performance

• Decreased feed intake, decreased body condition
• Decline in total pigs born per litter
• Increased stillborn rate
• Reduced litters farrowed per week
• Reduced feed intake
• Lower milk production
• Lower piglet birth weights
• Increased wean-to-estrus interval
• Reduced estrus signs

Gut wall degradation

Feed intake reduction and the decreased blood flow to the digestive tract can lead to a lower supply of oxygen and nutrients. This can influence the normal function of the intestinal barrier. Heat stress can alter the number and function of the enterocytes and reduce the digestive and absorptive capacity of the intestine.

Solutions

A specific approach has been designed for heat stress management in swine that targets the impact on the performance of the animal with specific reference to damage to the gut wall. With the world-leading monogastic live yeast, Saccharomyces cerevisiae var. boulardii CNCM I-1079, (brand name Levucell SB), developed by Lallemand Animal Nutrition, the intestinal microflora can be regulated. For a more targeted reduction of inflammation caused by heat stress in growers, Sangrovit enhances the resilience of the animals during this challenging phase. 

Levucell SB

• Specific live yeast for monogastric animals (Saccharomyces cerevisiae var. boulardii CNCM I-1079)
• 3 stage mode of action:
  1. Regulation of intestinal microflora
  2. Improves gut integrity
  3. Anti-inflammatory and immune properties

Sangrovit

• Regulation of inflammation
• Improved gut health
• Improved feed efficiency

Resources

Liu et al., 2009, Pearce et al, 2013, 2014
SE18GFPMAR0329 | University of Melbourne, AU | 2018 | Growing pigs