By Maude Richer-Lanciault
Editor’s note: Maude Richer-Lanciault is Monogastric Nutrition Manager, Trouw Nutrition. For more information, contact ‘lauren.dawson@trouwnutrition.com.’
With earlier and warmer temperatures during the summer, heat stress is a concern across Canada. Warm and humid weather can create sow performance issues in barns. With modern hyperprolific sows, this can be a real puzzle to solve. Weather cannot be controlled, but there are some solutions to help manage the impact of heat stress in sows.
Why are pigs sensitive to heat stress?
Pigs are particularly sensitive to heat stress because they do not sweat. To lower their body temperature, pigs will send more blood from the intestines to the skin surface to dissipate heat out to the environment. This can cause damage to intestinal cells due to a lack of oxygen. Thus, nutrient absorption decreases and the pig becomes more susceptible to pathogens, known as ‘leaky gut syndrome.’ With this, their feed intake and performance will decrease (Figure 1).
The genetics and physiological composition of domesticated pigs has changed considerably in recent years, and we have seen a significant decrease in fat deposition. From 1991 to 2001, the body lean tissue rate increased by 1.55 per cent. This increase of lean muscle increased metabolic heat production by 14.6 per cent. In turn, the increase in body heat production requires an adjustment to barn ventilation to remove this extra heat.
The thermoneutrality zone is the temperature zone in which pigs perform best. The ideal temperature for sows is 18 degrees-Celsius. At temperatures above 23 degrees-Celsius, sows begin to experience heat stress and their feed intake will start to be affected. Between 20 degrees-Celsius and 30 degrees-Celsius, feed intake will be reduced by 23 per cent. Ambient temperature is not the only factor that causes heat stress; humidity also plays a role. Depending on relative humidity, the apparent temperature may be different and is what the sow will feel. For example, a barn with high humidity of 80 per cent will be in heat stress danger at 26 degrees-Celsius, whereas another barn with similar temperature and 70 per cent humidity will be on heat stress alert (Figure 2). It is important to control the environment in your barn.
What can we do to support our sows during a heat stress period?
To support sows experiencing heat stress, the environmentin the barn should be monitored and adjusted appropriately, with consideration given to ventilation, cooling systems and heat pads for piglets. Drip cooling, by applying water on the pig’s skin, can have a cooling effect, potentially in combination with higher air speeds. Air movement is essential with this cooling technique due to the increase of moisture in the room. It is important to keep the sows and piglets comfortable. Care should be taken to avoid a draft on piglets, since newborn piglets have higher thermoneutrality than sows. Air quality should be assessed for the welfare of both animals and workers.
The quality and quantity of wateris extremely important for sows; it should always be readily available and be of good quality. Water quality assessments to determine mineral composition and microbiology should be performed before the summer. Water flow at multiple points should be verified. The barn should have enough water drinkers for the sows in the group housing section. Cool water will help the sows to better manage a high temperature.
If you see a change in the sows’ feeding patterns, match this pattern to your feed allocation program. Lactation feed should be available during cooler periods of the day, during early morning and late night, and feed should be kept fresh and clean to stimulate intake.
Using nutrition to combat heat stress
As heat stress reduces a sow’s feed intake, it can subsequently depress milk production, leading to reduced piglet body weight gain. Your nutritionist can work with you to find the best strategy for summer management in your barn. Many options are available, including solutions like adjusting the feeding program, the use of specific additives or changes in diet formulations.
Many tools can be used to adjust your feeding program during heat stress. For example, Trouw Nutrition’s NutriOpt Sow Model can determine the target feed intake according to different temperatures and evaluate the best density for your feed and customize the program according to your environment, genetics, performance and management.
An adjustment of the density of the feed can also support a lower feed intake during summer. For instance, a specific adjustment of amino acid ratios with energy, protein level, fibre and other nutrients can keep the feed balanced with higher density. Altogether, the goal should be to support sows’ needs and create less heat during the digestive process. It is also important to keep the feed very palatable to stimulate feed intake, as sows have excellent taste perception.
Oxidative stress impacts high-producing animals, especially under challenging conditions like heat stress. Antioxidants reduce the damaging effects of oxidative stress. The addition of an antioxidant package to the feed can support your sows during the heat stress period.
In a research trial, the addition of a mix of polyphenols – Trouw Nutrition’s Selko POmix flavour blend – increased sows’ reproductive performance, compared with a control group that only received Vitamin E. Polyphenols reduce lipid peroxidation before and during heat stress by decreasing malondialdehyde (MDA) production (Table 1). The addition of the flavour blend containing polyphenols increased lactation feed intake, increased the number of piglets weaned and increased litter weaning weight. Therefore, based on the results of this study, the use of polyphenols may increase the antioxidant capacity in sow diets to improve piglet performance while maintaining cost per piglet produced.
Several other additives are available on the market. For example, for leaky gut syndrome, adding antioxidants and osmoregulatory compounds, such as betaine, helps prevent the negative effects of heat stress in pigs. It is better to select the additive that will have the best return on investment and fit with your needs.
Heat stress impacts performance on multiple levels and can have large impacts on sow farms. It is best to adopt multiple strategies to reduce its negative effects. Farm strategies include ensuring water quality and availability for all pigs and adjusting the environment for the correct temperature and humidity in the barn. Feeding strategies include keeping your feed palatable and fresh, adding an antioxidant package or other additives, and adjusting the feed density. Your nutritionist can help evaluate these factors and recommend strategies to reduce the impacts of heat stress on your farm.
