Thermal stress can affect swine performance at both ends of the thermometer, especially in northern climates such as Minnesota, the Dakotas and Iowa. While heat stress gets a lot of attention globally, cold stress can also be significant.
Preparing for periods of thermal stress also requires forethought and planning, so producers are prepared and know what to do or what to expect, according to Julia Holen, a nutritionist with Swine Vet Center in St. Peter, Minnesota.
Going into winter, adverse weather conditions can affect not only livestock, which in the case of most swine are kept indoors in climate-controlled facilities year-round, but also equipment on farm as well as the ability to access farms to deliver feed and supplies.
"We recommend producers keep an eye on the weather and try to have backup feed on hand if a snowstorm hits, especially over a weekend, in case you can't get to the barn during the storm. It is also a good time to do maintenance checks on feed and water lines as well as ensuring ventilation systems and backup power systems are working properly," said Holen.
More specifically related to swine nutrition, Holen provides a few tips to consider for sows and grow-finish operations in the winter.
Ensuring sow feed intake
"As new-crop corn becomes available, corn and corn-DDGS should be tested for mycotoxins to understand what may be present in your region or from nearby feed mills," Holen said, explaining that different mycotoxins or a combination of mycotoxins can have varying effects on sow performance.
With new-crop corn entering sow rations, or really when any change is made to sow diets, Holen said it is a good time to recalibrate feeder settings within the gestation barn. She recommends checking at least 10 feed boxes for each box setting – the more the better – to ensure the sow is getting the expected quantity of feed. If the ration is formulated based on the expectation that sows are provided 4 lbs. but the feeder is actually delivering 3.5 lbs. on a true-weight basis, the sow may not be getting what she needs, Holen explained. On the other hand, if the sow is provided more feed than expected, sows can become over-conditioned during gestation.
"The volume of ingredients within diets can also affect feeder calibrations. Grain co-products such as DDGS, soy hulls, and wheat midds may have differing moisture content or volume that could impact the physical characteristics of the ration. Different batches of corn with differing test weights or moisture levels can have a similar influence on bulk density of the diet. Whenever there is a significant change to diet composition or ingredient sources, feeder boxes should be recalibrated to validate that sows receive an amount of feed that is expected based on feeder settings," Holen said.
"The first thing to understand on the grow-finish side for winter feeding is if the operation is under a fixed-time or a fixed-weight marketing strategy," Holen said, noting that the time and space available in a barn will affect pig feed intake and expected growth performance.
If a barn is long on space with no real time constraints, pigs often have more space than they need and may consume more feed than normal, she explained. Understanding the actual feed intake of growing-finishing pigs going into the winter months is key for producers to reach target market weights. In this scenario, growth rate of pigs may not be limited, however, the additional cost from higher feed intakes may not always provide a positive economic return.
If available pig space is short and time does become a limiting factor, nutritional strategies such as increasing energy concentration of the diet may support improved growth rates and fewer days to market.
Holen said it doesn't look like inclusion of dietary fats will be economical going into this winter but including high fiber ingredients such as dried distillers grains is likely to be economical. She said when rations push into the higher inclusion levels of DDGS, however, producers need to be mindful of the potential negative impact to carcass yield and may need to consider a step-down or withdrawal period with the final finishing diet right before marketing. "While it may be least-cost to include high DDGS throughout late-finishing, it may not have the greatest benefit or margin over feed cost due to lost carcass yield and potential impact on pork fat quality. I typically recommend stepping down DDGS inclusion prior to marketing, but every producer's economic scenario is different and must be considered."
Regardless of season, Holen said she is frequently asked if diets should be adjusted in case of a health challenge. She noted that there is a slight increase in energy and amino acid requirements for those pigs, but it is relatively small. Often-times, the reduction in feed intake and increased protein degradation that occur for health challenged pigs can't be compensated for through diet adjustments alone. Although we can make diet changes to try and help health-challenged groups, she said, simply getting pigs to eat can be the biggest hurdle to overcome.