The Problem: Summer Heat Hurts Pigs and Profits

Every summer, swine producers face a frustrating and expensive problem: carcass weights drop by an average of 6 to 12 pounds per pig, primarily due to heat stress. That might sound manageable—until you add it up. The estimated annual industry loss is a staggering $450 million (Schieck Boelke, 2024).

The issue isn’t just about temperature. Pigs naturally reduce feed intake when experiencing heat stress to lower metabolic heat production. But many standard feed formulations make the problem worse. Ingredients like corn DDGS, wheat middlings (a byproduct of wheat milling), and corn germ meal—commonly used in grow-finish diets—reduce feed intake even further. This nutritional “double whammy” limits growth just when pigs should be finishing strong, often during peak market prices in July and August.

High-energy diets fortified with fat were once a go-to solution, but today’s fat prices make that approach economically infeasible. As a result, nutritionists and producers are looking for alternative ways to maintain summer performance without breaking the feed budget.

The Insight: Rethinking the Role of Soybean Meal

Recent nutrition research and field trials highlight a strategic—but often overlooked—solution: soybean meal (SBM). While SBM is widely recognized as a high-quality protein source, its benefits extend beyond protein. The non-protein fraction of soybean meal contains valuable bioactive compounds—polyphenols, terpenoids, peptides, and functional fibers—that can support gut health, immunity, and growth during stressful periods. It also doesn’t result in suppressed feed intake like DDGS and other byproducts can.

“The persistent inferior carcass weight decline during the summer months remains a critical issue in the industry,” said Dr. R. Dean Boyd, a consultant for Nutrition Research, LLC, in a recent Swine Nutrition Blackbelt Podcast episode. “That decline in carcass weight and resulting financial losses during this period can be greatly minimized with the strategic use of higher levels of soybean meal in grow-finish diets.”

Dr. David Rosero, assistant professor of animal science at Iowa State University, echoed this recommendation. “You need to find the optimal level of soybean meal to support growth performance. Our field trials showed that diets high in soybean meal, with no DDGS or added fat, delivered the best performance and profitability during the summer,” he said.

The Solution: A Consistent, Sustainable Feeding Strategy

A summer feeding program that prioritizes soybean meal over DDGS and other feed intake-reducing ingredients offers a consistent, sustainable, and profitable approach to warm-weather nutrition. In field trials, this strategy led to:

Critically, this strategy should begin early. “You need to start feeding those pigs for summer in the spring,” said Dr. Rosero. “That way, by the time the heat hits, their diets are already optimized to maintain growth.”

Their findings are part of the Soy Effect research series funded by the United Soybean Board, which explores the nutritional and economic value of soybean meal in livestock diets. Learn more at soyeffect.ussoy.org.

Bottom Line: SBM Delivers When It Matters Most

For producers aiming to maintain consistent performance, reduce the sustainability footprint of their diets, and capture full carcass value in summer markets, soybean meal is more than just a protein source—it’s a heat-stress management strategy. By prioritizing profit margin over feed cost and making smarter ingredient choices, producers can turn the summer dip into a summer opportunity.

This article is funded in part by the soy checkoff.