All livestock producers are in a waiting game — waiting to see how short the 2012 corn crop will be, waiting to see where shortages will be felt deepest and waiting to see what adjustments will have to be made for quality.
In the past, drought conditions meant smaller kernels and lower test weights. But new corn varieties are more drought-tolerant, and yields and test weights may be different than we’ve seen in the past.
Experience has also taught us that drought-stricken feedgrains are more prone to molds and fungus, such as aspergillus, fusarium and gibberella. Each fungus has the potential to cause enough damage to the kernels to produce toxins detrimental to livestock.
As harvest progresses, some molds and fungus have been detected, but it is still too early to know how prevalent these problems will be.
Mold and Fungus
Drought-stressed grains are more susceptible to molds and funguses. Table 1 lists organisms important to livestock, the toxins they produce and concentration levels to consider.
Mold spores are present every year. But just because the organisms are present does not mean the toxins they produce are present. Black light screening is only an indicator that a mold or fungus is present. It does not qualify which are present or whether toxins have been produced.
In Iowa, agronomists have been scouting fields for weeks. In August, very few contaminated grains were found, but monitoring will continue through harvest.
Pork producers raising their own corn should be vigilant about monitoring fields. If problem organisms are detected, their concentration may vary not only from field to field, but also within a field. Whenever possible, high-concentration areas should be harvested and stored separately. Check with your agronomist for harvesting strategies and sampling procedures.
Co-products from processed grains concentrate the level of contamination by at least a factor of three, so consider having these ingredients tested before purchasing or using them in swine diets.
In 2009, high levels of vomitoxin were found across the Corn Belt, particularly in areas with hail damage and dry conditions. And vomitoxin has been more prevalent in barley and wheat.
Sourcing and using clean, high-quality grain are essential for the breeding herd and weanling pig-feeding programs. Speaking from experience, having fed barley contaminated with vomitoxin, some signs to watch for include:
• Fed to sows — Sows refuse feed in gestation and have late-pregnancy abortions, poor litter size, decreased birth weights and weaning weights.
• Fed in grow-finish — Pigs consuming contaminated diets were lighter and less uniform coming out of the nursery. Finishing pigs required an additional four to six weeks before reaching minimal selling weights.
The following year (2010), when pigs were fed good-quality corn and grew and converted diets better, many producers were caught off guard, sold hogs much heavier and were discounted because of the heavier carcasses.
Planting date, timing of rains and the severity of the drought all add to the variability of grain quality.
The test weight of a bushel is not only important for corn, but also for all grains used to feed livestock. Low test weight usually means less starch — lower energy — within the kernel and, consequently, slightly higher protein levels. When formulating swine diets on an amino acid basis, it is important to know that amino acid levels in grains change at a different rate than protein.
When diets are manufactured with low-test-weight grains, pigs may eat more to compensate for the lower energy content. University studies have shown that low-test-weight corn doesn’t significantly affect growth rate, but feed conversion may decline slightly.
Shorter Shelf Life
Another detriment of low-test-weight grain is its shorter shelf life. Corn with a 50-lb./bu. test weight may have half the shelf life of corn with a 56-lb./bu. test weight.
Grain test weight and the anticipated length of storage should be factored into feeding programs — particularly in drought-stressed grains that we will likely see this crop year.
If lower-test-weight corn is harvested and stored on farm, grain quality should be closely monitored throughout the winter and spring. Grain quality may be compromised in late spring or summer, so additional sampling and testing may be required.
Feedmills, grain dealers and ethanol plants all understand the damaging effects of molds and funguses on livestock performance. Talk with each supplier about their sampling procedures and the reports they have available. These suppliers and your area Extension agent may also be able to refer you to testing labs capable of testing farm-stored grains. State veterinary diagnostic labs also have the capability to test grains and feed samples for contamination. Costs generally vary from $30 to $120, depending on the test and the number of toxins being considered.
If fields and grains are contaminated with molds and funguses, caution should be taken against exposure to the spores and toxins. Contaminants may be threshed out of the grain and expelled in the discharge behind the harvester or in the chaff as grain is augered into wagons or bins. Protective eyewear, dust masks and/or gloves should be worn by personnel handling or moving grains.