Due to increased global temperature, desert encroachment, deforestation and heat waves, climate change will add to the burden of heat stress, particularly in tropical regions and during summer. Higher temperatures result in lower fertility rate, decreased feed intake and reduced growth rate in pigs
Moderate warming and more carbon dioxide in the atmosphere may help some plants to grow faster. However, more severe warming, floods, and drought may reduce yields. Livestock may be at risk, both directly from heat stress and indirectly from reduced quality of their food supply.
Thomas Bach, President of the International Olympic Committee said on the 23rd July 2024, a few days before the opening of the games in Paris 2024 that the hot weather may well affect the performance of numerous athletes. Swine genetics is no different and the modern sow is leaner and more sensitive than her counterpart of twenty years ago to both high and low temperatures. This includes her progeny.
What are factors affecting swine production?
There are five important areas:
• Management. The quality of this contributes to the health and biological efficiency of the pig.
• Feed.
• The type of housing used and the quality of the environment.
• The levels of disease and their economic effects.
• The genetic potential of the pig.
Projections based on a global temperature rise of 1.5°C by the end of the twenty-first century, and on labour force trends, suggest that, in 2030, 2.2 per cent of total working hours worldwide will be lost to high temperatures – a productivity loss equivalent to 80 million full-time jobs.
If this is what can happen to businesses, what about agribusiness and in particular pig production?
Pigs prefer temperatures between 15 to 21 degrees Celsius (60 to 70 degrees Fahrenheit).They have limited ability to regulate their body temperature, so extreme heat or cold can cause discomfort and stress.
Quick facts
Pork producers should not overlook the effects of heat stress. Heat stress causes:
• Lower feed intake in grow-finish pigs during the summer.
• Harmful effects in the sow herd during breeding, gestation and lactation.
• Lasting harmful effects in offspring of sows that had heat stress during pregnancy.
It is important to prevent heat stress to limit these harmful effects.
We will discuss a little later in more detail
Ideal temperatures for housed pigs
As a pig gets older and heavier, its ideal temperature declines. Heat stress is a greater concern in older finishing pigs (greater than 50kg) as well as sows and boars than in younger pigs.
Heat stress begins to affect sows, boars and finishing pigs at about 21֯ C. If temperatures remain above 28֯ C for more than two to four days, decreases in performance and reproductive efficiency can result if cooling relief is not available.
Ideal temperatures for housed breeding and grow-finish pigs
| Animal age weight | Ideal temperature (C) | Desirable temperature limits (C) |
| Lactating sow | 16 | 12 – 21 |
| Litter, newborn | 35 | 32 – 37 |
| Litter, 3 weeks old | 28 | 25 – 32 |
| Nursery, 6-15 kg | 26 | 21 – 30 |
| Nursery, 15 – 35 kg | 22 | 18 – 28 |
| Grow – finish pigs | 18 | 14– 26 |
| Gestating sows | 16 | 12 -24 |
| Boars | 16 | 12 -22 |
Effect of heat stress on weaner and grower pigs:
Heat stress can have significant adverse effects on weaner and grower pigs. These effects can impact their health, growth performance, and overall welfare. Here are some key points on how heat stress affects these pigs:
Physiological Effects
1. Respiratory Rate: Heat stress increases the respiratory rate as pigs attempt to cool down through evaporative cooling.
2. Body Temperature: Core body temperature rises, leading to hyperthermia if not managed.
3. Metabolic Changes: There are changes in metabolism, including increased maintenance energy requirements and alterations in nutrient utilization.
Health Effects
1. Immune Function: Heat stress can suppress the immune system, making pigs more susceptible to diseases and infections.
2. Dehydration: Increased panting leads to higher water loss, and if not adequately compensated, it can cause dehydration.
3. Heat Stroke: In severe cases, prolonged exposure to high temperatures can result in heat stroke, which can be fatal.
Growth Performance
1. Feed Intake: Pigs under heat stress tend to reduce their feed intake, which directly affects growth rates and feed efficiency.
2. Weight Gain: Reduced feed intake and changes in metabolism result in lower weight gain.
3. Carcass Quality: Heat stress can negatively affect carcass quality, leading to less desirable meat characteristics.
Behavioral Changes
1. Activity Levels: Pigs may reduce their activity levels to minimize heat production.
2. Feed and Water Consumption Patterns: Pigs may change their feeding and drinking behavior, often eating more during cooler parts of the day.
3. Social Interactions: Stress can lead to changes in social behavior, including increased aggression or lethargy.
Management Strategies
1. Cooling Systems: Providing adequate cooling systems such as fans, sprinklers, or misters to help pigs dissipate heat.
2. Shade and Ventilation: Ensuring sufficient shade and proper ventilation to reduce ambient temperature.
3. Nutritional Adjustments: Modifying diets to be more nutrient-dense and providing electrolytes to counteract the effects of heat stress.
4. Water Availability: Ensuring constant access to fresh, cool water to prevent dehydration.
Implementing these management strategies can help mitigate the negative effects of heat stress on weaner and grower pigs, improving their health, growth performance, and overall welfare.
Effect of heat stress on breeding sows
Heat stress can have profound and detrimental effects on breeding sows, impacting their reproductive performance, health, and overall welfare. Here are the main areas affected by heat stress in breeding sows:
Reproductive Performance
1. Reduced Conception Rates: Heat stress can lead to lower conception rates due to decreased fertility in both sows and boars.
2. Embryo Survival: High temperatures can reduce the survival rate of embryos, leading to increased early embryonic death.
3. Estrous Cycles: Heat stress can disrupt normal estrous cycles, causing irregularities and anestrus (absence of estrus).
4. Litter Size: Sows exposed to heat stress during gestation may have smaller litters due to increased embryonic mortality.
Health Effects
1. Reduced Feed Intake: Like other pigs, breeding sows reduce their feed intake under heat stress, leading to poor body condition.
2. Dehydration: Increased respiratory rates and panting lead to higher water loss, increasing the risk of dehydration.
3. Increased Susceptibility to Diseases: Heat stress can suppress the immune system, making sows more prone to infections and illnesses.
Physiological Effects
1. Hormonal Changes: Heat stress can alter hormone levels, including cortisol, which can affect reproduction and overall health.
2. Thermoregulatory Responses: Sows may pant excessively and exhibit other thermoregulatory behaviors to cope with high temperatures.
3. Increased Heart Rate and Respiratory Rate: To dissipate heat, sows’ heart rates and respiratory rates increase, which can stress their cardiovascular and respiratory systems.
Behavioral Changes
1. Reduced Activity: Sows may become lethargic and reduce their physical activity to minimize heat production.
2. Altered Feeding and Drinking Patterns: Sows might change their feeding and drinking behavior, consuming more water and feed during cooler parts of the day.
3. Agitation and Discomfort: Prolonged exposure to high temperatures can cause agitation and discomfort, impacting sow welfare.
Farrowing Performance
1. Prolonged Farrowing: Heat stress can lead to prolonged farrowing times, increasing the risk of complications for both sows and piglets.
2. Lower Piglet Viability: Piglets born to heat-stressed sows may have lower birth weights and reduced viability.
3. Increased Stillbirths: There is an increased risk of stillbirths in sows that experience heat stress during late gestation.
Management Strategies
1. Cooling Systems: Implementing cooling systems such as fans, evaporative coolers, and misters can help maintain a comfortable environment.
2. Ventilation: Ensuring proper ventilation to reduce ambient temperature and humidity in the housing facility.
3. Shade and Shelter: Providing adequate shade and shelter to protect sows from direct sunlight and high temperatures.
4. Nutritional Adjustments: Offering nutrient-dense diets and ensuring constant access to fresh, cool water to maintain hydration and energy intake.
5. Scheduling: Adjusting breeding and farrowing schedules to cooler times of the year can help reduce the impact of heat stress.
By addressing these areas, producers can help mitigate the negative effects of heat stress on breeding sows, thereby improving their reproductive performance, health, and overall welfare.
Selection for increased leanness has led to increased heat production of growing pigs. The more productive an animal is, the more heat they produce. This extra heat makes pigs less tolerant of external heat. As a result, they are more prone to heat stress than less productive pigs. In response to heat stress, these pigs will decrease feed intake to reduce the heat they make. Reduced feed intake reduces growth rate.
Pigs raised in heat-stress settings will have more fat deposits than pigs raised in cooler settings. Increased fat results because the pig’s body changes how it uses nutrients. Nutrients are put towards more fat growth than protein growth in heat-stressed pigs consuming less feed.
Studies looked at the effects of heat stress experienced by sows during gestation on the piglets in the sow’s uterus. Piglets born to sows that experienced heat stress during pregnancy had increased core body temperature, which makes them more prone to heat stress after birth. Changes in metabolism also occur in these offspring, which results in less skeletal muscle and more fat tissue being deposited during the growth stage
When hell freezes over
Cold pigs are literally high maintenance.
Cold pigs, even mature pigs, require more feed to maintain heat production and body condition. Growing pigs living in cold conditions will have poor feed conversion rates, increased feed intake, and will likely struggle to grow without free access to good feed and housing keep warm. How much feed does it take to maintain body weight or growth in cold temperatures? Depending on the age and size of pig, and outside temperatures and weather conditions, you may need to increase the daily feed allowance by 3x or more.
It is important to maintain the pig within an equitable temperature range and this is called the thermo-neutral zone. It is dependent upon the type of floor, its insulation properties, the air speed and temperature and the insulation of the building.
This is particularly so if the pig is at a critical time in relation to disease challenge, or when under environmental stress. For example, if it coincides with a move from solid concrete or straw bedded floors to concrete slats. The temperature requirement for the pig might have been 20ºC (68ºF) before the move but could well be 25ºC (77ºF) for the first days in the new accommodation. Pigs that are within their comfort zone will lie on their sides barely touching their neighbours.
The point at which pigs must increase heat production to keep warm is called the lower critical temperature (LCT). Many factors affect this including body weight, feed intake, age, insulation of the building and particularly the floor type. There is an upper critical temperature (UCT) and the range between the upper and lower ones is called the thermo-neutral zone.
Adverse cold temperatures have effects at the following critical times:
• From birth to 48 hours.
• From 8-14 days of age.
• From weaning to 7 days post-weaning.
• On movement from first to second stage weaner accommodation.
• A change in the type of flooring e.g. solid to slats, bedded too non-bedded.
• A change of housing or nutrition.
• A change in stocking density.
• A move from dry to wet feeding.
• A move to poorly insulated houses.
• Movement into a wet house.
• Fluctuations in external temperatures due to ventilation and air speed.
• Faulty environmental controllers.
• Low energy diets or unpalatable feed.
• Restricted feeding.
• Failure to eat sufficient feed.
• Thin pigs.
• Disease.
• The sow during lactation.
• From weaning to 21 days post-mating.
• In the last six weeks of pregnancy.
• Draughts at any age can result in the pig experiencing significantly lower temperatures than might be registered by an air temperature thermometer. This is the wind chill factor.
Economics 101
For every degree below the LCT (lower critical temperature) a growing pig loses approximately 10-12g of liveweight gain per day. A level of 1ºC below the LCT during the growing period could cost R30- 50 in extra feed per pig during the grower period.
• To produce a baconer of 80 kg requires approximately 280 kg of feed (HFCR 3.5)
• A kilogram of feed costs on average R7.70/kg
• The value of an extra pig born per litter is R270
• The value of 100 grams of weaner mass is R8.00. Producers can calculate their performance losses or gains
Climate Change Challenges for Pig Farmers
Productivity
• Heat stress could result in reduced productivity (including fertility problems)
• Summer infertility is a well-known multifactorial syndrome.
• Possible reduced water availability from suppliers or on-farm sources in some regions.
• Reduced feed intake in hot weather negatively affects performance and productivity
• Potential for increased/different diseases and increased veterinary and medicine costs
• Reduced grass cover and persistence (in outdoor systems)
Costs
• Possibly increased capital, maintenance and energy costs for ventilation/cooling/heating/odour and emission control
• Requirement for improved housing management during extreme weather events
• Increased unpredictability of extreme weather events
• Global feed prices may be affected by climatic changes or other market mechanisms and products
Adaptation Suggestions for Pig Farmers
• Improve insulation of buildings to control internal temperatures more effectively and reduce energy wastage
• Design ventilation control systems to manage changing climatic conditions
• Use enclosed creep boxes in farrowing houses to better regulate the environment for piglets and sows
• Select grass or cover crop varieties that can cope with changes in the climate to prevent soil erosion
• Improve design and management of wallows and shaded areas
• Invest in water storage facilities, e.g. on farm reservoirs
• Use less intensive rearing techniques e.g. outdoor (but recognise this impacts on water pollution and soil erosion and take preventative steps to manage these)
Mitigation Measures for Pig Farmers
Although some of the impacts might happen to a greater or lesser extent in the short, medium or longer term, it is important to think ahead for the future, especially in relation to issues such as building design and breeding patterns.
Conclusion
• Modern pig production is a highly intensive business.
• Capital expenditure, especially related to modern housing is extensive and expensive.
• Concentrating on environmental factors can be as financially rewarding as the negativerewards of not taking it into consideration.
Pieter Grimbeek
Thank you to Jurgens Reynders for proof reading and offering valuable advice.
References:
University of Minnesota Extension Office
The Pig Site
BRF Ingredients Website
Lallemand Website