Swine heat stress peaks in July; pig farmers need to take preventive measures early

In July, Anhui Province enters the period of high temperature and intense heat, and a heatstroke prevention warning has been issued for the @#@227@#@ industry. With the scaling up and intensification of the pig industry, increased herd density, and the main pig breeds being foreign three-way crossbreds, pigs are more prone to heat stress. How to control heat stress in pigs during summer has become one of the important tasks for pig farmers.

Heat stress is an invisible killer

Compared with epidemic diseases, the damage caused by heat stress to pig farms is often invisible.

The most suitable temperature range for growing-finishing pigs is 18-21°C, and 32-38°C falls within the heat stress range. When the temperature is 5-10°C above the optimum, the feed intake of pigs decreases by 6%-21%; heat stress causes a decline in feed intake.

Under heat stress conditions, sows show a decreased conception rate, an increased number of stillborn piglets at the end of gestation, and reduced litter weight, and may even abort. Sows may also experience reduced feed intake, leading to a decline in both the quality and quantity of milk in lactating sows, ultimately affecting piglet survival rate and weaning weight.

Hot weather weakens the mating desire of boars and lowers semen quality. High temperatures reduce the semen volume of boars and decrease the proportion of live sperm and total sperm count; the fertilization rate is 85%-90% at 20°C and 50%-60% after 2 hours of exposure at 33°C. The effect of high temperature on boar semen quality can even last for up to 3 months. One of the reasons for sows returning to estrus and the decline in litter size in the second half of each year is high temperature.

Pig farming requires attention to methods

First, ventilation and insulation. Pig farms should first be built in open areas with good ventilation, oriented facing south, and in our province open or semi-open pig houses that can use natural ventilation are preferable. Fans or blowers can also be installed to promote air flow, effectively reduce air humidity, and carry away heat inside the house; longitudinal ventilation is more effective than transverse ventilation. Planting tall trees around the pig farm and pig houses can reduce sunlight exposure.

Second, spraying to cool down. Evaporative cooling is the most effective method. When the house temperature is too high, a hose or sprayer can be used to periodically spray water on the pigs' bodies (except in farrowing houses) and roofs to cool them, or water can be sprinkled manually. For sows in gestation crates and farrowing houses, a drip cooling system can be used. For empty and pregnant sows and growing-finishing pigs, spraying or showering can be used; cooling is fast, and the house temperature can be lowered by 5-8 degrees within 5-10 minutes. However, spraying (sprinkling) water to cool down will increase humidity inside the house; high temperature and high humidity will aggravate heat stress and can also cause the spread of pathogenic microorganisms within the house.

Third, wet curtain fan cooling. The wet curtain fan cooling system was originally used for summer cooling in breeder chicken houses and can lower the house temperature by 5-7°C. The drier the air and the higher the temperature, the greater the cooling range of the air passing through the wet curtain, and the more significant the effect. Wet curtain cooling is currently more suitable for boar and sow houses, and the cost is relatively low.

Fourth, air conditioning cooling. Air conditioning cooling can not only lower the temperature but also control humidity, but the cost is too high. However, for breeding pig farms and production farms using artificial insemination technology, centralized management of boars and installation of air conditioning are still worthwhile, as they can significantly improve boar semen quality in summer.

Pay attention to diet in hot weather

In hot weather, pigs need attention to their diet. For example, using different feed formulas during high temperatures, adding various trace elements and minerals, and increasing green feed are all simple and effective measures.

First, adjust the feed formula. In high temperatures, in order to reduce body heat increment and reduce the burden of heat dissipation, pigs will inevitably reduce feed intake, resulting in insufficient intake of energy, protein and other nutrients and affecting pig growth and development. Making necessary adjustments to the feed formula is one of the effective measures to overcome heat stress. Since the more heat increment from nutrients, the greater the burden on pigs for heat dissipation and the more severe the heat stress, choose ingredients with good palatability and fresh, high quality to compound the diet, appropriately reduce the proportion of high-fiber ingredients, and control the crude fiber level of the diet to reduce the production of body heat increment.

Oil and fat have small volume, high net energy value, and low body heat increment, making them an ideal energy source for pigs under high temperature conditions; oil and fat can be added to feed at no more than 5%. Under heat stress, pigs' protein requirements increase, so increasing the crude protein content in feed can improve feed utilization and reduce the burden of heat dissipation in pigs during hot weather. Adding 200-500 mg/kg vitamin C and 200 mg/kg vitamin E to feed can enhance resistance to heat stress, increase feed intake and daily gain. Appropriate addition of sodium bicarbonate (250 mg/kg) and the trace element potassium can also alleviate the adverse effects of heat stress on pigs. Providing an appropriate amount of green feed to boars and sows can improve herd appetite and stress resistance.

Second, strengthen management. Reducing stocking density can lower the temperature inside pig houses. Ensure water supply, change dry feeding to wet feeding or use pelleted feed, which can increase pig feed intake. Adjust feeding times, increase the number of feedings, feed earlier in the morning and later in the afternoon, avoid feeding during the hottest times, and add one feeding at night. Avoid mating during high-temperature periods or even seasons.

Third, add anti-heat-stress medications. Adding sucrose, electrolytes and other components to drinking water can significantly improve feed conversion; when the temperature exceeds 34°C, anti-heat-stress medications such as vitamin C, vitamin E, biotin and choline may be used as appropriate; adding 10 mg/kg daidzein or 400 mg/kg taurine to feed can also reduce the impact of heat stress on growing-finishing pigs. Supplementing pig feed with 300 micrograms/kg chromium (chromium picolinate) can alleviate the effects of high-temperature stress, increase pig feed intake and daily gain, and reduce the feed-to-gain ratio. Chromium needs a period of time to take effect (after 2 weeks). Some Chinese herbal medicines can coordinate the physiological metabolism of pigs under high temperature, promote pig growth and development, and improve immune function. Chinese herbal medicines with the functions of stimulating appetite, strengthening the spleen, clearing heat and relieving summer heat, such as hawthorn, Atractylodes lancea, dried tangerine peel, areca nut, Scutellaria baicalensis and Daqu, can be made into feed additives to alleviate the impact of high temperature on pigs and improve weight gain and feed utilization.

Chinese herbal medicines, vitamins, minerals, electrolytes and other ingredients are compounded into additives in certain proportions, which can coordinate the regulatory functions within the pig's body and enhance the pig's adaptability and ability to resist high temperatures, thereby alleviating heat stress in pigs.