Effect of reduced CuSO 4 inclusion on growth performance, meat yield and economics of grower-finisher pigs
This study demonstrates that reducing dietary copper sulphate to 75 mg/kg in grower-finisher pigs maintains growth performance and carcass quality while maximizing economic returns and supporting more sustainable production by lowering feed costs and copper excretion.
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In the world of pig farming, feed is the single largest expense, often accounting for up to seventy percent of the total cost to raise an animal. To ensure these animals grow quickly and efficiently, farmers have long relied on adding specific minerals to their diet. One such mineral is copper, usually supplied in the form of copper sulphate. While pigs need small amounts of copper to stay healthy and support their immune systems, farmers have historically added much larger, "pharmacological" doses to their feed. The belief was that these high levels acted as a growth booster, altering the bacteria in the pig's gut to help them digest food better and gain weight faster. However, this practice has a significant downside. Pigs do not absorb all the copper they eat; a large portion passes straight through their bodies and ends up in their manure. When this manure is spread on fields as fertilizer, the copper accumulates in the soil, potentially harming the environment, contaminating water, and contributing to the rise of bacteria that are resistant to treatment. As regulations tighten and environmental concerns grow, the question has become whether these high doses are truly necessary, or if farmers can reduce them without hurting their animals or their profits.
A team of researchers at the University of KwaZulu-Natal set out to find the answer by testing different levels of copper in the diets of growing pigs. They worked with 352 pigs, a mix of males and females, starting when the animals were about ten weeks old and weighing roughly 33 kilograms. The pigs were divided into groups and fed one of four different diets over a twelve-week period. The only difference between the diets was the amount of copper sulphate added: one group received 25 milligrams per kilogram of feed, another received 75 milligrams, a third received 125 milligrams, and the final group received the traditional high level of 175 milligrams. The researchers carefully monitored how much each pig ate, how much weight they gained, and how efficiently they converted that food into body mass. At the end of the trial, the pigs were processed to measure the weight of their carcasses, the percentage of lean meat, and the overall financial return for the farmer, including the cost of the feed and the revenue from selling the meat.
The results showed that the pigs performed remarkably well regardless of how much copper they received. The animals in all four groups grew at nearly the same rate, ate similar amounts of food, and converted their feed into body weight with equal efficiency. There was no clear advantage for the pigs fed the highest levels of copper in terms of how fast they grew or how much meat they produced. In fact, when the researchers looked closely at the data, they found a subtle but important pattern regarding the final weight of the meat. The pigs fed the moderate level of 75 milligrams of copper per kilogram of feed tended to have the heaviest carcasses, while those fed the highest level of 175 milligrams actually produced slightly lighter carcasses than the moderate group. This suggests that adding more copper beyond a certain point does not help the animal grow better and might even be counterproductive.
The most significant finding, however, came from the financial analysis. Because copper is an ingredient that costs money, the price of the feed increased steadily as the amount of copper in the diet went up. The feed with the lowest copper content was the cheapest to produce, while the feed with the highest copper content was the most expensive. When the researchers calculated the profit margin—the money left over after paying for the feed—they found that the highest profit was not made with the cheapest feed, nor with the most expensive one. Instead, the best financial return was achieved by the group fed the 75 milligram level. This group generated the highest revenue per pig and the greatest profit margin, outperforming the groups fed both lower and higher doses. The data indicated that the extra cost of adding high levels of copper simply ate into the farmer's profits without providing any extra growth or meat to sell.
These findings suggest that the traditional practice of feeding pigs very high doses of copper is no longer necessary for optimal production. By reducing the copper in the diet to a moderate level of 75 milligrams per kilogram, farmers can maintain the same high quality of growth and meat yield while saving money on feed costs. This adjustment also offers a clear environmental benefit. Since pigs excrete most of the copper they eat, feeding them less copper means less copper ends up in the manure, reducing the risk of soil contamination and the spread of resistance genes in the environment. The study concludes that a moderate level of copper supplementation is sufficient to support healthy, productive pigs, offering a path toward a farming system that is both more profitable and more sustainable. While the research was conducted on a single farm, the results provide a strong indication that the industry can move away from excessive mineral supplementation without compromising the quality of the food produced.
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