Greg Horstmeier News Director 573-884-1846 horstmeierg@missouri.edu April 2, 2003 Hot cows may get stress relief from a cooling dose of seaweed COLUMBIA, Mo. -- When cattle can't stand the heat, they do more than get out of the kitchen. They leave the dining room. Heat stress has long been known to reduce weight gains, cut milk production, increase reproduction problems and even kill cattle in extreme cases. A team of University of Missouri researchers has found that a small amount of a commercial seaweed meal, Tasco-14, offers some respite for cattle in heat stress. Animal stress physiologist Don Spiers and livestock nutritionist James Williams recently completed the first round of studies using a seaweed meal, containing Ascophyllum nodosum in cattle diets. The product is processed by Acadian Agritech of Nova Scotia, Canada. Williams and Spiers presented their results at the Midwest meetings of the American Society of Animal Science in Des Moines, Iowa. "Heat stress can come from many factors," Williams said. "Extremely hot weather can cause weight gains to drop, of course. But stress can also come from the toxic effects of cattle feeding on endophyte-infected fescue pastures or hay." Most summer fescue pastures naturally contain the endophyte fungus. Though this fungus helps the forage grass survive tough Midwestern growing conditions, it also makes cattle and other ruminants sick, which causes their internal body temperatures to rise. Cattle with this toxicosis-induced hyperthermia have poorer weight gains, poorer reproduction rates, and generally perform poorly compared to cattle fed uninfected forages. Combine endophyte-infected summer pastures with a 98-degree day, and cattle get a double-whammy of heat stress. In one study, Spiers and Williams fed part of a group of cattle a grain-based diet that included 1 percent Tasco-14. "Previous tests have shown that the 1-percent level of the meal produces a fairly consistent response in cattle," Spiers said. Further testing is required to confirm how a 1-percent Tasco diet affects cattle under different degrees of heat stress. They fed the steers in climate-controlled growth chambers. "We found that steers fed the seaweed meal had lower body temperatures several days into a high-heat period," Spiers said. "Eventually, treated cattle begin to have the same internal body temperatures as non-treated cattle, but there is definitely a short-term drop in temperature." That drop caused the treated animals to gain an average of 13 pounds more weight during the test than heat-stressed animals not fed the meal. Spiers saw equivalent short-term temperature drops and weight gains in previous studies using rats. In another research trial, he and Williams placed the steers from the 40-day chamber study on tall fescue pastures for 60 days from June through July without any additional seaweed meal. Half of the cattle were placed on endophyte-infected tall fescue pastures, half on endophyte-free tall fescue pastures. Temperature sensors recorded a short period where steers previously fed Tasco-14 and grazing infected tall fescue pastures had lower internal body temperatures than those never given the meal. "Now we want to look for the optimum feeding strategy that will take best advantage of this temperature drop," Spiers said. "If we can get only a week's advantage, when is the best time to feed the product and then take the animals off of it before a period of hot weather comes in? Or, is there a strategy of putting cattle on the product, taking them off it, and then on it again to get that body-temperature drop more than once during the season?" Those questions must be answered before Spiers and Williams can answer the biggest one: How does the meal work in the first place? "We really don't know what is going on in the animal," Williams said. "It could be one compound, it could be a combination of things that are in there. So we also need to look at some of the specific compounds to see if we can figure out exactly which is giving the benefit." "We do know that, although it is actually bringing down body temperatures, it's not really counteracting the fescue toxicosis," Spiers added. "We see the same short-term temperature drop when animals are subjected to heat stress alone and do not eat infected fescue." Williams also has tested the product's influence on forage digestibility and has seen a slight advantage in fiber digestibility unrelated to the heat-stress benefit. "We hope to get the funding to continue the cattle studies," Spiers said. "There is something happening here that could be a benefit to producers. We just have to figure out how to get the most economic advantage from it." Source: Don Spiers (573) 882-6131 James Williams (573) 882-7345 Return to Current News Releases College of Agriculture Food and Natural Resources AgEBB