Sows suffer during the summer, especially sows of modern genetics during the lactation period.
Whereas the maintenance needs of a gestating sow are met by a mere 2-3 kilograms feed per day, a lactating sow nursing 14 piglets requires at least 2+(14×0.5)=8 kilograms feed per day. They rarely reach that high level of feed intake, and this is why they milk their offspring by burning their body fat and muscles. And, during summer’s heat stress times, feed intake drops even further, resulting in even worse condition for sows and low weight for piglets at weaning.
The reason sows do not consume as much feed as they need especially during the heat stress periods is because feed processing generates heat. Standing up, chewing and swallowing feed, having it digested and absorbed, and then metabolized, converted into milk with waste being excreted are some of the major processes that all produce heat, as inevitable loss due to general thermodynamic laws. And, when the animal tries to minimize heat stress by any means, eating a hearty meal is no way to achieve it. Thus, the general observation among farmers and scientists alike is that heat-stressed animals consume less feed. But, there are ways to partially alleviate this, some of which involve nutrition.
When it comes to nutrition, there are two areas where we can help sows cope with summer heat stress: one has to do with diet design and the other with feeding management. But it is not always easy to achieve a desired outcome as more factors come into play than those described here. For this reason, the advice of a qualified nutritionist should always be sought for best results.
Adjusting nutrients in feed
Nutrient density. It is generally assumed that some part of the normal nutrient intake can be maintained during the summer months if nutrient density increases proportionally to the expected reduction in feed intake.
For example, if feed intake is expected to drop by 10%, then all nutrients (including vitamins, minerals and trace minerals) should be increased by 10% to compensate for the reduction in feed intake. For several nutrients, however, there are manufacturing limits that may restrict the application of this strategy. For example, it is not always practical to add more than 6-8% fat in commercial diets. Also, the concentration of certain additives cannot be altered due to country-specific regulations. Therefore, this strategy should always be combined with another one to increase effectiveness.
In addition, it might not be financially viable to provide a very dense diet as there is the law of diminishing returns when more expensive ingredients are required to enter formulation.
Dietary protein. Excess protein is invariably deaminated and excreted in the form of urea. This process requires energy and generates heat and, to this end, it is highly recommended to reduce excess dietary protein concentration with the aid of feed-grade amino acids.
The extent of reduction is a matter of diet formulation, available ingredients and cost of feed-grade amino acids as the diet must remain balanced in all amino acids. This is the area where most errors are made, but it can provide great relief to a heat-stressed animal.
Fiber concentration. Fiber digestion and metabolism generate considerably more heat compared with carbohydrates and protein, with fat and lipids generating the least amount of internal heat. Thus, one of the more common measures to combat heat stress is to reduce dietary fiber (again the exact level of reduction depends on initial concentration and other factors as described above).
Care should be taken for sows to be supplemented with a strong laxative (usually in the form of a salt) to compensate for the reduction in dietary fiber. Nevertheless, a good balance of fermentable and insoluble fiber fractions should be maintained to ensure proper functionality of the digestive system, especially to avoid upsetting the health of the hindgut ecosystem.
Fats and oils. Following from the above, it appears that fats and lipids not only increase dietary density, but they also generate less heat during digestion and metabolism. Therefore, diets high(er) in fat and lipids are almost invariably recommended for combating heat stress.
However, it is always imperative to also increase (proportionally) the levels of all amino acids and other nutrients, to avoid unbalancing diets. Here, dry fat (expensive) or extruded full-fat soybeans are quite useful in creating a balanced new summer formula when adding extra straight oil or fat is not possible.
Additives. Research and practical experience has clearly demonstrated that adding certain additives may actually improve feed intake in lactating sows. Some additives work through enhancing nutrient digestibility, others by increasing palatability, yet others by controlling internal metabolic processes reducing release of heat. The selection of proper additives is very crucial because they can easily become very expensive if they offer no real advantage.
Extra vitamins. In other monogastric species, certain vitamins have been shown to help animals under heat stress. This is a new area for pigs that continues to receive little attention. In particular, it appears that water-delivered vitamins offer some additional benefits.
Adjusting feeding management
Pelleted diets. Pelleting diets increases physical density, resulting in higher uptake of nutrients at a given volume of feed. Combined with increased nutrient density, these two strategies help markedly in sustaining higher nutrient intake during heat stress.
Liquid diets. One of the major benefits of liquid feeding is that an animal can consume more feed during the summer months. Perhaps the increased intake of water enables them to better control their internal temperature compared with dry-fed pigs. Or, liquid diets are easier to ingest, and perhaps even more palatable than dry diets.
Cool water. It has been shown that pigs provided with cool water during periods of heat stress are able to sustain better performance. In addition, pigs offered cool water consumed less water per day compared with control pigs, indicating that cooler water enabled pigs to quickly adjust their body temperature in response to heat stress. Finding cool water in most farms is a challenge, unless such water is provided by deep wells.
Feeding time. Feeding in the cooler evening hours, or even during the night, has been used as an effective measure against severe summer heat. This might create an increase in labor costs, but it is one single very effective method. Lamentably, it is also one of the least followed worldwide.
Feeding frequency. Smaller and more frequent meals will prevent sows from overloading with food and creating an overload of heat released during a short period of time. The exact number of additional feedings depends on available labor, but even going from the normal two to three times per day can provide some relief.