Practical methods for relieving heat stress in pig farms
Methods for relieving heat stress in pig farms
A hot, high-temperature environment can cause an imbalance within the body of meat pigs. In order to maintain the stability of the internal environment, the body makes an adaptive response to the stressor (high temperature). Excessive stress in the body often leads to a decline in the production performance of meat pigs, and in severe cases can lead to shock or even death. During the process of technical guidance and follow-up services for pig farming, the author has had extensive contact with specialized breeding households, and now offers his own views on the prevention of heat stress in meat pigs.
1 Effects of heat stress on meat pig production
The suitable temperature for meat pig growth is 15°C to 25°C, and 32°C to 38°C is generally considered the heat stress range. When the air temperature is 21°C, meat pigs gain weight best; below or above this temperature, pig growth is affected. When the environmental temperature rises, pigs show reduced activity and feed intake, increased drinking, slower growth, and may even show reduced eating.
High temperatures are very unfavorable to pig growth and fattening, and sensitivity to air temperature rises as body weight increases. Tests show that for pigs weighing 45 kg, when the air temperature exceeds 32°C, weight gain drops noticeably; for pigs weighing 75 kg in the late fattening stage, in an environment below 25°C, there is no significant difference in monthly weight gain; but in a heat stress environment above 30°C, their feed intake and weight gain both decline significantly. The main reason for the decline in pig body weight is the reduction in feed intake caused by heat stress.
2 Measures to relieve heat stress
Pigs under heat stress not only experience disorders in physiological functions, decreased feed intake, and slower weight gain, but may even show adverse phenomena such as weight loss.
2.1 Create suitable environmental conditions
Doing a good job of environmental greening helps improve the microclimate conditions inside the pig farm.
Planting vines such as grape, luffa, fingered citron, and gourd outside the pig pen and letting them climb over the pig pen roof: on the one hand, the green vegetation blocks direct exposure of the pen and roof to the scorching sun and plays a cooling role; on the other hand, grapes, luffa, and the like can also be obtained, achieving two benefits at once.
Coat the outer walls of the pig pen with white material to enhance light reflection, reduce solar radiant heat, and relieve heat stress.
Plant fast-growing poplars around the pig pen; in 2 to 3 years they can provide shade and shelter, reducing heat stress in meat pigs, and after the leaves fall in autumn and winter they do not affect sunlight for the meat pigs.
Install electric fans inside the pig house for mechanical ventilation, forcibly expel the foul air inside, speed up air convection inside and outside the house, and create a cool and comfortable environment.
During sudden high temperatures or continuous high temperatures, cold water can be sprayed on the ground, walls, and roof of the pig house, and when necessary directly sprayed on the pigs to achieve the purpose of preventing heatstroke and cooling.
2.2 Feed watermelon
From early summer to early autumn, when watermelons are on the market, agreements can be signed with watermelon growers to use some smaller watermelons that cannot fetch a good price to feed pigs. These watermelons or watermelon rinds are very cheap, and some can even be obtained without spending money, but for pigs they are a good heatstroke-preventing and cooling food.
2.3 Supply sufficient, cool, and hygienic drinking water
Water plays an important role in regulating body temperature, so under heat stress conditions clean, sufficient, and hygienic cool water must be supplied, with deep well water being best, and attention should be paid to changing it frequently.
2.4 Arrange feeding times reasonably
Because temperatures in the morning and evening are relatively lower and pigs have a relatively stronger appetite, feeding at these times can increase feed intake.
2.5 Do not make stocking density too high
In summer, avoid a rise in house temperature caused by high stocking density. Generally, for pigs below 60 kg, the floor area per pig should be no less than 0.7 sq m; for pigs above 60 kg, no less than 1 sq m per pig is best.
2.6 Increase the energy level in the daily ration
To relieve the decline in production performance of pigs affected by a high-temperature environment, a more nutrient-rich daily ration should be given during hot seasons to make up for the insufficient energy intake caused by high temperatures. Because pigs under heat stress have a higher digestibility of dietary fat than of other nutrients, adding 2% to 3% fat to the pig's daily ration can, on the one hand, increase the energy level of the ration and stabilize the pig's weight gain rate, and on the other hand can also improve feed palatability, increase feed intake, ensure energy intake, and thereby promote growth.
2.7 Supplement limiting amino acids in the daily ration
Under heat stress, the crude protein content of the daily ration needs to be adjusted. Feeding synthetic lysine to replace natural protein is beneficial to pigs. Supplementing 0.3% lysine in the daily ration can reduce heat consumption from the ration and significantly improve feed conversion rate and pig production performance.
2.8 Supplement sodium bicarbonate in the daily ration
Sodium bicarbonate has wide sources and a low price, and has the effects of dissolving mucus, strengthening the stomach, inhibiting acid, and increasing appetite. After being absorbed into the body, it can supplement the sodium needed by the body and serve as a major buffering substance in blood and tissues, alleviating respiratory alkalosis and improving the ability to resist heat stress. Adding 0.5% sodium bicarbonate to the feed is the best way to overcome the acid-base balance disorder and blocked production performance caused by heat stress.
2.9 Supplement vitamin C and vitamin E
During heat stress, vitamin C helps maintain a relatively high feed intake, thereby ensuring sufficient nutrient supply and resisting the adverse effects of heat stress. At the same time, vitamin C can synthesize the steroid hormone corticosterone, strengthen the body's immune function, and reduce the mortality rate of meat pigs under high temperatures. Adding 400 mg/kg vitamin C to the meat pig daily ration can improve the body's immunity, effectively relieve heat stress, and improve production performance.
Vitamin E also has a certain role in resisting heat stress. During heat stress, some changes occur inside the body's cells, so adding vitamin E can stimulate immune organs, enhance the body's immunity, and help improve the ability to resist stress. Adding 200 IU/kg vitamin E can effectively relieve heat stress in meat pigs and improve production performance.
2.10 Use anti-stress drug additives
During heat stress, the body temperature of pigs increases. To reduce unnecessary muscle activity and heat production, sedative drugs can be used to inhibit the central nervous system and body activity, thereby reducing the effects of heat stress; chlorpromazine or diazepam can be added to the feed. In addition, zinc bacitracin 100 mg/kg or flavomycin 2.5 mg/kg + oxytetracycline 50 mg/kg can also be used, which helps enhance livestock disease resistance, inhibit the reproduction of harmful bacteria in the intestinal tract, promote growth, and improve feed utilization rate, while also having a certain effect on relieving heat stress.
2.11 Use Chinese herbal medicine additives
Chinese herbal medicines contain abundant vitamins, trace elements, and other active ingredients, can enhance the body's immunity, and comprehensively coordinate physiological metabolism, thereby playing a role in relieving heat stress. Chinese herbal medicine feed additives for resisting heat stress have the functions of stimulating appetite and strengthening the spleen, clearing heat and detoxifying, and removing heat and relieving summer heat. Commonly used Chinese herbal medicines include: bupleurum, reed root, licorice, dandelion, wild chrysanthemum, scutellaria, ageratum, honeysuckle, isatis root, atractylodes, gentian, eleutherococcus, and so on; these medicines can be mixed into the feed as a formula for feeding.
1 Effects of heat stress on meat pig production
The suitable temperature for meat pig growth is 15°C to 25°C, and 32°C to 38°C is generally considered the heat stress range. When the air temperature is 21°C, meat pigs gain weight best; below or above this temperature, pig growth is affected. When the environmental temperature rises, pigs show reduced activity and feed intake, increased drinking, slower growth, and may even show reduced eating.
High temperatures are very unfavorable to pig growth and fattening, and sensitivity to air temperature rises as body weight increases. Tests show that for pigs weighing 45 kg, when the air temperature exceeds 32°C, weight gain drops noticeably; for pigs weighing 75 kg in the late fattening stage, in an environment below 25°C, there is no significant difference in monthly weight gain; but in a heat stress environment above 30°C, their feed intake and weight gain both decline significantly. The main reason for the decline in pig body weight is the reduction in feed intake caused by heat stress.
2 Measures to relieve heat stress
Pigs under heat stress not only experience disorders in physiological functions, decreased feed intake, and slower weight gain, but may even show adverse phenomena such as weight loss.
2.1 Create suitable environmental conditions
Doing a good job of environmental greening helps improve the microclimate conditions inside the pig farm.
Planting vines such as grape, luffa, fingered citron, and gourd outside the pig pen and letting them climb over the pig pen roof: on the one hand, the green vegetation blocks direct exposure of the pen and roof to the scorching sun and plays a cooling role; on the other hand, grapes, luffa, and the like can also be obtained, achieving two benefits at once.
Coat the outer walls of the pig pen with white material to enhance light reflection, reduce solar radiant heat, and relieve heat stress.
Plant fast-growing poplars around the pig pen; in 2 to 3 years they can provide shade and shelter, reducing heat stress in meat pigs, and after the leaves fall in autumn and winter they do not affect sunlight for the meat pigs.
Install electric fans inside the pig house for mechanical ventilation, forcibly expel the foul air inside, speed up air convection inside and outside the house, and create a cool and comfortable environment.
During sudden high temperatures or continuous high temperatures, cold water can be sprayed on the ground, walls, and roof of the pig house, and when necessary directly sprayed on the pigs to achieve the purpose of preventing heatstroke and cooling.
2.2 Feed watermelon
From early summer to early autumn, when watermelons are on the market, agreements can be signed with watermelon growers to use some smaller watermelons that cannot fetch a good price to feed pigs. These watermelons or watermelon rinds are very cheap, and some can even be obtained without spending money, but for pigs they are a good heatstroke-preventing and cooling food.
2.3 Supply sufficient, cool, and hygienic drinking water
Water plays an important role in regulating body temperature, so under heat stress conditions clean, sufficient, and hygienic cool water must be supplied, with deep well water being best, and attention should be paid to changing it frequently.
2.4 Arrange feeding times reasonably
Because temperatures in the morning and evening are relatively lower and pigs have a relatively stronger appetite, feeding at these times can increase feed intake.
2.5 Do not make stocking density too high
In summer, avoid a rise in house temperature caused by high stocking density. Generally, for pigs below 60 kg, the floor area per pig should be no less than 0.7 sq m; for pigs above 60 kg, no less than 1 sq m per pig is best.
2.6 Increase the energy level in the daily ration
To relieve the decline in production performance of pigs affected by a high-temperature environment, a more nutrient-rich daily ration should be given during hot seasons to make up for the insufficient energy intake caused by high temperatures. Because pigs under heat stress have a higher digestibility of dietary fat than of other nutrients, adding 2% to 3% fat to the pig's daily ration can, on the one hand, increase the energy level of the ration and stabilize the pig's weight gain rate, and on the other hand can also improve feed palatability, increase feed intake, ensure energy intake, and thereby promote growth.
2.7 Supplement limiting amino acids in the daily ration
Under heat stress, the crude protein content of the daily ration needs to be adjusted. Feeding synthetic lysine to replace natural protein is beneficial to pigs. Supplementing 0.3% lysine in the daily ration can reduce heat consumption from the ration and significantly improve feed conversion rate and pig production performance.
2.8 Supplement sodium bicarbonate in the daily ration
Sodium bicarbonate has wide sources and a low price, and has the effects of dissolving mucus, strengthening the stomach, inhibiting acid, and increasing appetite. After being absorbed into the body, it can supplement the sodium needed by the body and serve as a major buffering substance in blood and tissues, alleviating respiratory alkalosis and improving the ability to resist heat stress. Adding 0.5% sodium bicarbonate to the feed is the best way to overcome the acid-base balance disorder and blocked production performance caused by heat stress.
2.9 Supplement vitamin C and vitamin E
During heat stress, vitamin C helps maintain a relatively high feed intake, thereby ensuring sufficient nutrient supply and resisting the adverse effects of heat stress. At the same time, vitamin C can synthesize the steroid hormone corticosterone, strengthen the body's immune function, and reduce the mortality rate of meat pigs under high temperatures. Adding 400 mg/kg vitamin C to the meat pig daily ration can improve the body's immunity, effectively relieve heat stress, and improve production performance.
Vitamin E also has a certain role in resisting heat stress. During heat stress, some changes occur inside the body's cells, so adding vitamin E can stimulate immune organs, enhance the body's immunity, and help improve the ability to resist stress. Adding 200 IU/kg vitamin E can effectively relieve heat stress in meat pigs and improve production performance.
2.10 Use anti-stress drug additives
During heat stress, the body temperature of pigs increases. To reduce unnecessary muscle activity and heat production, sedative drugs can be used to inhibit the central nervous system and body activity, thereby reducing the effects of heat stress; chlorpromazine or diazepam can be added to the feed. In addition, zinc bacitracin 100 mg/kg or flavomycin 2.5 mg/kg + oxytetracycline 50 mg/kg can also be used, which helps enhance livestock disease resistance, inhibit the reproduction of harmful bacteria in the intestinal tract, promote growth, and improve feed utilization rate, while also having a certain effect on relieving heat stress.
2.11 Use Chinese herbal medicine additives
Chinese herbal medicines contain abundant vitamins, trace elements, and other active ingredients, can enhance the body's immunity, and comprehensively coordinate physiological metabolism, thereby playing a role in relieving heat stress. Chinese herbal medicine feed additives for resisting heat stress have the functions of stimulating appetite and strengthening the spleen, clearing heat and detoxifying, and removing heat and relieving summer heat. Commonly used Chinese herbal medicines include: bupleurum, reed root, licorice, dandelion, wild chrysanthemum, scutellaria, ageratum, honeysuckle, isatis root, atractylodes, gentian, eleutherococcus, and so on; these medicines can be mixed into the feed as a formula for feeding.