Prevent Heat Stress, Lowered Productivity: Monitor Moisture and Mycotoxins


        The heat is on and it's seriously affecting the agriculture industry in the Northeast and beyond. The intense heat is combined with the most severe and extensive drought in 25 years, according to the United States Department of Agriculture. This combination has wreaked havoc on more than 62 percent of the nation's farms. Declared drought disasters by the USDA, these areas of the US may see crop yields reduced by 60 to 100 percent. Even here in the Northeast, where loss may not be as staggering, the problems from out west will keep feed prices high and local farmers will still have to watch out for increased nitrate and mold levels in their own crops.

        According to Dr. Swamy Haladi, global technical manager of the Alltech Mycotoxin Management Team, drought not only causes obvious losses in crop yield but brings more mycotoxins to the farm as plants become stressed and more susceptible to diseases. "It is not just excess rain that brings with it the increased mycotoxin challenge but historically the worst mycotoxin years are also drought years," Haladi said.

        Mycotoxins are harmful compounds produced by molds (fungi) that are found in soil and can grow on vegetable matter including grain, forages and silages. Mycotoxins can be formed in the field pre-harvest and may continue to be formed under suboptimal storage conditions post-harvest. Temperature is an important factor influencing mold growth and mycotoxin production and plants stressed by drought and high temperatures are commonly invaded by mold spores, which can produce mycotoxins. Insect challenge in the field is directly proportional to temperature and such damage reduces the plant protection against molds. The fact that some of the crop producers are not spraying fungicides to keep the cost down only compounds the problem.

        "The global climate change has resulted in climatic extremes which are increasing the frequency of mycotoxin contamination we are seeing in our cereal grains, forages and silages," Haladi said.

        No matter what the cause, all the elements associated with drought are precursors for Aspergillus and some of the Fusarium molds such as Fusarium verticilloides and Fusarium moniliforme. Aspergillius molds produce Aflatoxin B1, the notorious carcinogen mycotoxin regulated by the FDA.  Haladi recommends producers take field checks to look for grayish, yellow green mold near the tips of or all over the ears. Producers should check in several areas of the field to be sure.

        While the Midwest may be used to seeing incidences of vomitoxin (DON) and zearalenone, Haladi warns that this year may be worse due to the dry conditions and insect damage. Such conditions allow some Fusarium molds to produce another group of mycotoxins called fumonisins. These toxins can compromise immune and gut systems at lower concentrations but cause pulmonary edema (fluid accumulation in lungs) at higher concentrations.

        According to Dr. Elizabeth Santin in The Mycotoxin Blue Book, Fusarium species can survive in corn residue, which is probably the most important source of inoculums for kernel infection. These fungi can be associated with every part of the corn plant and 50 to 100 percent incidence of kernel infection is not uncommon, with the majority of kernels showing no visible damage.

        This year's corn harvest may also suffer from additional setbacks. Many experts have recommended that farmers let the corn plants grow more and not chop too early to aid in nitrates. However, farmers should still monitor moisture levels.

        "Silage that is too dry, less than 65 percent moisture, will not pack well," Haladi said. "This situation can increase the chances of Penicillum molds from making an appearance in our silage. Unlike other mycotoxins, these silage mycotoxins can act as antibiotics and kill beneficial microbes in the rumen. The net result is lowered productivity."

        Haladi also warns if producers are cutting the silage lower to increase tonnage, they may also be increasing the amount of soil contamination and thus further increasing the amount of mold spores.

        "Producers should positively identify any situations that may arise with this year's corn crop and not assume it is only Aspergillius," Haladi said.

        In order to indentify more of the risks associated with mycotoxins, Alltech recently launched its 37+ Program. The mass spectrometry technique LC-MS2 can investigate 38 different mycotoxins quantitatively, and more than 50 others qualitatively in less than 15 minutes per sample analyzed, with limits of detection in the parts per trillion range.

         "This approach allows us to have a broader analytical approach compared to the other commercial methods that can only see a 'snapshot' of contamination," Haladi said.

        Once mycotoxins have made their way into the feed, there are still a few options available to producers. They can choose not to feed the contaminated feed or they can use an effective mycotoxin adsorbent. There are two types of adsorbents: silica-based polymers and carbon-based organic polymers. Silica-type materials, such as clays, are readily available and many have shown to be effective against aflatoxins but ineffective against other types of mycotoxins. Haladi recommends an organic mycotoxin sequestering agent that can be used at practical levels of inclusion for all species of mycotoxins, including DON.

        "Our livestock remains the best indicator of a mycotoxin presence," Haladi said. "If an animal is not performing to its fullest or unexplained symptoms persist; consider the role that a mycotoxin may be playing."

Keep them cool too
        Our fields aren't the only ones battling the dry conditions and increased temperatures.  Our livestock have also been suffering. As of July 17, approximately 73 percent of cattle areas were affected by moderate to intense drought. The USDA expects the combination of heat stress and higher feed costs to restrain growth this year on U.S. cattle and hog numbers as well as poultry and milk production.

        Many producers are concerned about the economic losses. Between $1.69 and $2.36 billion is estimated to be lost each year due to heat stress in the United States. The dairy industry accounts for $897 to $1500 million and the beef industry for $370 million (St-Pierre et. al., 2003) of these losses.

        Dr. Max Hawkins, Alltech, explains that producers need to keep in mind the Temperature-Humidity Index (THI). THI is a combination of temperature and relative humidity to create a value for heat stress. At 80 degrees Fahrenheit there is no stress until 30 percent relative humidity; after 30 percent there will be mild stress. At 90 degrees Fahrenheit, the cows are already in mild stress up to 30 percent relative humidity. At 100 degrees Fahrenheit, cows are in mild stress up to 50 percent humidity and above that they are in moderate.

        Signs of heat stress in livestock and poultry range from an elevated breathing rate, restlessness, and drooling, animals standing in pens and grouped together in Stages 1 through 3 to labored breathing, decreased heart rate, tongue protruding, open mouth breathing, head down and isolation in Stages 4 through 6. Typically for dairy cows, heat stress is noticed in the production of less milk with lower milk fat and protein. 

        "These take approximately three days to be seen," Hawkins said. "Initially, the cows will have a higher respiration rate (80 per minute), more standing, less dry matter intake, more water consumption and seeking the shade or cooler locations."

        He suggests calling a veterinarian when body temperature is over 102.5 degrees Fahrenheit, there is increased ketosis, and the respiration rate is over 90.

Hawkins recommends the following management tips to prevent heat stress:

.    Provide adequate shade, fans, misters.

.    Provide extra cooling in holding areas, cool water.

.    Use propionic acid to prevent feed heating in bunk.

.    Feed multiple times and at cooler parts of the day to encourage intake.

.    Keep feed pushed up and as fresh as possible to enhance intake.

        "Reduced feed intake is a main effect of heat stress," Hawkins said. "The loss of nutrition intake needs to be of concern to maintain cow performance and health."
According to Dr. Mike Hutjens, University of Illinois, producers should consider the following nutrient guidelines during periods of heat stress:

· Maintain 20 to 22 percent effective NDF (neutral detergent fiber) in the ration to maintain cud chewing and forage raft in the rumen.

· Limit total crude protein to less than 18 percent on a dry matter basis with 6.5 to 7 percent as RUP (rumen undegraded protein).

· Maintain 28 to 30 percent NDF, 18 to 20 percent ADF (acid detergent fiber).

· Target 24 to 26 percent starch and 4 to 6 percent sugar to adjust the rate of carbohydrate fermentation in the rumen and favor microbial growth.

· Raise DCAD over 350+ meq per kg.

· Increase total ration potassium to 1.4 to 1.6 percent, sodium to 0.4 to 0.5 percent, and magnesium to 0.35 percent.

        Feed additives can also be beneficial. According to Hutjens, yeast culture and fungal products can help to stabilize rumen pH and improve the rumen environment while maintaining fiber digestion. These products can also reduce lactic acid levels in the rumen that can drop rumen pH.

        Alltech's Yea-Sacc®1026, a live yeast culture based on Saccharomyces cerevisiae strain 1026 and part of the Alltech Dairy Advantage program, has been shown to improve fermentation efficiency, which can decrease body temperature. Yea-Sacc1026 also modifies the rumen environment, which can help cows withstand heat stress and achieve greater levels of animal performance.

        A recent trial initiated in Italy used two groups of 49 cows to investigate the supplementation of Yea-Sacc1026 on cows fed a combined diet of maize silage, alfalfa hay and grain-based mixed feed.  Only one group received 10 grams per head per day of the live yeast culture. The results showed an improvement in milk yield and a two percent increase in daily dry matter intake for the cows fed Yea-Sacc1026. On average, feed efficiency was improved by three percent, increasing from 1.25 to 1.28 kilograms milk per kilograms of dry matter intake, with the effect being more marked during the summer season where heat stress situations were reported

        The Alltech Dairy Advantage series of natural solutions is aimed directly at optimizing rumen efficiency and maintaining animal health as well as reducing mastitis, lameness and fertility issues. For more information, contact your local Alltech sales representative or e-mail

By Evan Wisell, Regional Sales Manager, Alltech