There is never a time in swine production where producers aren’t facing challenges in some form or fashion. Many challenges – whether they are nutritional, health or management related – tend to be seasonal. Fall is typically a favorite season for many producers, lending optimized weather conditions for growth. But, hot summer temperatures bring on a distinct set of obstacles.
Heat stress, for example, is a concern in the summer – especially when hot temperatures are combined with high humidity. The optimal temperature for pigs post weaning is between 65°F and 75°F. In this temperature range, pigs remain in their thermoneutral zone. In the thermoneutral zone, swine can maintain their core body temperature without altering feed intake, behavior or metabolism. Body heat production is also at its lowest in this zone. When the temperature reaches beyond the upper range of the thermoneutral zone, pigs are unable to dissipate heat without expending extra energy. Instead, heat loss occurs through panting. Additionally, pigs may exhibit signs of heat stress, increasing water intake and reducing activity – including eating. There are also other physiological changes such as increased blood cortisol, increased oxidative stress, increased inflammatory cytokines, increased blood pH (respiratory alkalosis), alterations in intestinal microflora, reduction in blood flow to the intestines and other internal organs and loss of intestinal integrity. Ultimately, in addition to being a welfare issue, heat stress leads to economic loss from decreased performance, reduction in meat quality and increased mortality.
In addition to heat stress, there are also health management considerations in the summer. Maintaining gut health and immune function is crucial to help optimize production during summer months. The intestines are one of the first organs impacted by summer heat and are responsible for both nutrition absorption and keeping toxins and bacteria out of the pig.
As with health, there are also nutritional considerations. Summer weather presents optimal conditions for mold growth, providing exposure to adequate moisture and heat. If not controlled, mold growth can lead to a decline in feed quality through loss of nutrients and vitamins. Additionally, molds can produce mycotoxins which lend their own detrimental effects, including loss of intestinal integrity and impaired immunity. There is also the risk of feed rancidity, which can reduce the fat energy levels in the feed, as well as the availability of fat-soluble vitamins.
Although we face many of the same issues from summer to summer, here are a few reminders on how to combat summertime challenges through management, nutritional and health interventions.
1. Adapt Your Formula for the Season
Negative performance during the summer primarily happens due to reduced feed intake. To counteract pigs backing off feed due to heat stress, there are several adjustments that can be made to dietary formulas. Formulation of nutrient dense diets can help pigs maintain nutrient intake while eating less feed. Increasing energy levels in diets may also compensate for reduced feed intake. Because protein digestion produces higher levels of metabolic heat, this is often accomplished by increasing fat levels and lowering protein. If protein levels are reduced, however, amino acid levels must be carefully balanced to compensate for example through synthetic amino acid and/or enzyme supplementation. Also avoid feeding during the peak heat stress time of day (10:00AM-4:00 PM) to increase feed intake and reduce feed wastage.
2. Maximize Feed Quality and Consider Pellet Feeding
While pigs can lose nutrients through reduced feed intake, they can also lose nutrients by having poor feed quality. Warm temperatures and high humidity lend opportunistic growing conditions to molds. Molds can reduce feed quality by utilizing the nutrients in the feed before it gets to the pigs. In addition, the mycotoxins produced by molds negatively affect almost all organ systems of the pigs along with reducing performance and feed efficiency. Performance loss from molds and mycotoxins can be combatted, by adding mold inhibitors and flow agents to feeds. Similarly, antioxidants can protect fats and oils in feed from becoming rancid through oxidation. There is also evidence that pellet feeding during summer could help with mitigating the performance loss during summer.
3. Supplement with Vitamins, Minerals and Systemic Antioxidants
Supplementation with vitamins and other additives can be useful in mitigating the effects of heat stress. Vitamins A, E and C supplementation may be beneficial not only because they are antioxidants and heat stress may cause oxidative stress in pigs, but also because they are not synthesized as readily in heat-stressed pigs. Mineral supplementation is also helpful. Selenium – also an antioxidant – can be added to ameliorate the effects of oxidative stress. Minerals such as calcium, zinc, phosphorus and magnesium, that are critical to growth and development, are lost either through reduced appetite or from lowered metabolism during heat stress. These minerals should also be properly balanced and if needed, supplemented to counteract this loss. Other minerals, such as chromium, directly combat heat stress by reducing cortisol levels. Supplementation with chromium can therefore improve growth rate and yield during heat stress. Additionally, it is critical to address electrolyte loss and acid-base imbalance due to respiratory alkalosis from panting. Salts such as sodium bicarbonate and potassium chloride can be added to the feed to maintain acid-base balance. Electrolytes may also be supplemented in the water on very hot periods.
4. Address the Immune System
One of the many detrimental effects of heat stress is an impaired immune system. Excessive heat tends to impair the ability of pigs to elicit optimum immune responses to vaccine and to fight off pathogens. While many producers associate the summer with less risk of disease and may use a less aggressive immune vaccination program during the summer months, it is critical that focus must be given to these programs. One way to help is to perform diagnostic surveys periodically in a subset of pigs to ensure that the vaccination program being used matches the challenges in the pigs. In addition, it is important to evaluate the efficiency of programs by looking at vaccine application and titers. Further, managing acute and chronic stress such as caused by heat stress is important to have a well-balanced immune system to fight off other challenges. A balanced diet with optimum amino acid ratio and minerals like zinc, copper and chromium have the potential to mitigate chronic stress and help keep the immune system balanced and ready for any challenges during summer. Feeding immune modulators like β-glucans, ideally before the start of summer, stimulates the immune system delicately without too much activation so that the animal is ready to face any immune and pathogenic challenges.
5. Focus on Diseases Through Proper Record Keeping
While historic data indicates that diseases in summer are less prevalent compared to winter, proper measures should be taken to protect the animals from diseases which are less prevalent, but become more aggressive, during summer. Prevalence of gastric ulcers and ileitis caused by Lawsonia increases during summer months. In grow-finish pigs, salmonellosis favors summer months compared to other seasons. While the number of erysipelas cases might be lower during summer months, there is some evidence that acute erysipelas seems to be more severe in summer months. While all three diseases have effective vaccines, it is important to follow the proper vaccination programs to prevent the outbreaks of these diseases during summer. Apart from these diseases, outbreaks during summer varies greatly from one farm to the other, and by geographical location. Proper record keeping is the key to identify and keep a check on diseases specific to a particular farm.
6. Focus on Maintaining Gut Health
A good intestinal health program is essential for a successful operation for all seasons, but it’s even more important during summer. The gastrointestinal (GI) tract is one of the first organ systems which gets affected severely during heat stress because the animal diverts blood flow to the peripheries to dissipate the heat. Also, the wide swings in temperature with the varying humidity during the different parts of the day in the summer contributes to high heat index and impacts the GI tract of the pigs significantly. The issues that result from an unhealthy gut are twofold. Firstly, as mentioned earlier, pigs tend to eat less during summer – consuming lesser nutrients than what is typically needed for optimum growth and production. If the intestine is not healthy and not working efficiently, this will compound the health issues significantly. Secondly, any pathogen or other toxic insult which enter the pig’s bloodstream because of the damaged intestine has the potential to start an inflammatory cascade –diverting vital nutrients which may already be in a deficient state. Gut health is of paramount importance to overcome any stress successfully. Probiotics, short chain fatty acids like butyric acid, minerals like zinc and copper, osmolytes, certain phytobiotics and antioxidants help maintain gut health during heat stress.
7. Ensure Ample, Clean Water Availability
Pigs consume more water as the temperature rises. It is important to have clean, cool water available to dissipate heat. Pigs should have a sufficient amount of drinker nipples/bowls and water pressure in each pen, and they should be properly maintained. Flushing lines regularly can help keep water clean and cool, which encourages pigs to drink more. As pigs drink more water, it attenuates the stress and feed intake tends to follow.
8. Maintain Evaporative Cooling Systems
Evaporative cooling systems need to be maintained to optimize cooling. Cool pads can lower the temperature in the barn significantly and combat heat stress, but there are factors that can lower the efficiency of systems. It is most important that pads and pipes don’t become clogged. Dirt and debris should be removed mechanically from pads and mineral deposits, and scale should be removed with a cleaner. Filters should also be flushed prior to use. Algae can clog pads and should be avoided by cleaning, limiting exposure to sunlight and allowing pads to dry out once a day. Wet-skin cooling using sprinkler systems or water-drop cooling are also desirable methods for the cooling of pigs.
9. Provide Adequate Ventilation and Floor Space
During the summer, it is critical to remove heat from the barn. Be sure to provide proper air flow uniformly throughout for tunnel ventilation. This can be accomplished by making sure barns are tightly sealed, and there are no holes in the walls or ceilings. It is also critical to have the correct number of fans and check that they are in good condition. This means ensuring fan belts are not loose, as well as making sure fan blades and shutters are clean as dust and loose belts can reduce airflow. Bearings should also be lubricated if needed. It is also desirable during summer to reduce stocking density to provide more floor space per pig to prevent crowding and overheating particularly in heavier pigs. Ideally, 1-3 pigs should be reduced from each pen depending on the nature of temperature extremes. Also, to reduce the stress to the pigs, handle them only during the cooler parts of the day, either in the morning or evening.
Finally, keep in mind that for an exceptional producer, the welfare of the pig should be the ultimate goal. All aspects of pig rearing are interconnected, and everything should be given equal attention. All the points discussed here provide a holistic approach toward the health and welfare of the pig. Utilized appropriately, they should provide the ideal growing condition for the pig and would allow the pig to realize its true genetic potential.
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