After the Cold Dew solar term, new corn from North and Northeast China gradually comes into storage. Bright in color, fragrant, and inexpensive, it tempts many pig farmers to grind it and add it to feed right away to save on feed costs.
But after just a few days, problems arise: the pigs develop diarrhea, with undigested corn kernels in their feces. They eat plenty but show no weight gain; some eat less or vomit, while sows develop swollen, red vulvas and come into heat irregularly. Instead of saving money, they end up losing it.
New corn is a good feed ingredient, but freshly harvested corn really should not be fed to pigs directly. Today, we’ll explain what you need to know. Follow these steps, and you can still raise healthy pigs with new corn.
Corn drying after the autumn harvest
I. The “temperament” of new corn: it has not fully “ripened” yet
Many people think that once corn has been dried, it is ready. In fact, corn is a crop that continues to mature after harvest and needs to undergo “secondary maturation.”
In freshly harvested corn, most of the starch is resistant starch, also called macromolecular polysaccharides. This starch is highly viscous and difficult to digest. Enzymes in a pig’s small intestine have difficulty breaking it down, so it cannot be absorbed after ingestion. The corn needs to be stored in a well-ventilated, dry warehouse for a period of time before the resistant starch gradually converts into normal starch that pigs can absorb and use. This process generally takes 5 to 6 weeks, or about a month and a half.
That is why pigs fed a lot of new corn grow slowly: the energy is not absorbed and is all excreted in the feces.
Fresh corn also has a high moisture content. The safe moisture content for corn used in feed is generally required to be below 14%, but newly harvested corn typically has a moisture content of 15% to 20% in North China, and 20% to 30% in Northeast China and Inner Mongolia. High moisture content dilutes the energy, disrupts nutritional balance, and makes the corn particularly prone to heating and mold.
II. Three common pitfalls when feeding pigs new corn
Pit one: diarrhea and undigested feed
This is the most typical presentation. The feces are loose and unformed, with whole or broken corn kernels visible in them. In the industry, this is called “feed passage.” The root cause is resistant starch and high moisture content. Indigestible starch enters the hindgut and ferments; at the same time, the energy in the diet is diluted and the protein proportion rises relatively. Pigs cannot digest it, resulting in nutritional diarrhea. Piglets’ intestines are not yet fully developed, so they show the most pronounced reaction, and often the entire litter develops diarrhea.
Pitfall two: Mycotoxins, the invisible pitfall
Newly harvested corn has high moisture content and strong respiration, and threshing inevitably produces some broken kernels, making it prone to heating and mold during storage. A special reminder: mold does not grow only in storage facilities; corn may already be contaminated while growing in the field. About one quarter of corn has been contaminated by mold around the time of harvest.
There are three common types of toxins, each of which harms a different area:
·Aflatoxin: damages the liver and suppresses immunity, lowering pigs’ resistance and making them more susceptible to illness; severe cases can be fatal.
·Vomiting toxin (DON): Pigs may refuse feed, reduce their feed intake, or even vomit, which is a major reason their feed intake fails to increase.
·Zearalenone: harms reproduction, causing swelling of the vulva, false estrus, and repeated failure to conceive in sows. Replacement gilts are particularly at risk.
As for toxins, corn can look perfectly fine and still exceed the limit; you can’t sort them out just by looking.
Pitfall three: High feed intake, a high feed-to-meat ratio, and slow growth
New corn has a low actual energy value. Pigs may eat more to make up for the energy shortfall, but they cannot absorb what they eat. As a result, feed intake increases, daily weight gain does not, and the feed-to-meat ratio actually rises. When you do the math, using cheaper new corn may result in higher pig-raising costs.
Here’s a counterintuitive point: during the new-corn phase, never try to make up for energy by adding extra fat. Fat can worsen diarrhea, defeating the purpose.
Three. How should you use new corn? Remember the five steps
New corn can be used; it just needs to be used the right way. The core approach comes down to nine Chinese characters: control moisture, allow it to age, and transition steadily.
Step one, sun-dry or heat-dry until the moisture content is below 14%. After harvesting, dry the crop in the sun or with heat as soon as possible. It is best to check the moisture content before storage and use, keeping it within 14%. Do not let the drying temperature exceed 60℃. Excessive heat can denature starch and damage vitamins, which can impair digestion.
Step two: Allow it to mature fully, and leave it for one and a half months. After drying, winnowing, and removing impurities by sifting, put it into storage in a cool, ventilated, dry place for 5–6 weeks. Use it once the resistant starch has been almost fully converted. This is the easiest and most effective method. Keep the warehouse temperature below 24℃ and the relative humidity below 80%.
Step three: If you need to use it urgently, mix new and old corn and transition gradually. If you can't wait a month and a half, feed a mixture of new corn and high-quality old corn, gradually increasing the proportion of new corn and extending the transition period to more than a month. You can follow this schedule: feed new and old corn at a ratio of 4:1 for half a month, then 3:1 for half a month, then 2:1 for half a month, and only then switch completely to new corn. Never switch everything at once; the pigs' intestines and gut flora won't be able to handle it. Monitor their stools closely while changing feed. If they develop diarrhea, immediately reduce the amount or stop feeding it.
Step four: Winnow and sieve, then add a mold inhibitor and enzyme preparation. Before use, sieve and winnow the grain to remove as many broken kernels, impurities, and moldy kernels as possible. Add a mycotoxin binder to the complete feed (such as montmorillonite or yeast cell wall products; generally, add 1–2 kilograms per ton of feed, following the product instructions). To address resistant starch, add a compound enzyme containing amylase and glucoamylase to help break it down. Pay particular attention to controlling zearalenone in sow and gilt feed. If possible, have new corn tested for toxins before use.
Step five: Don’t grind the feed too finely; prepare homemade feed as needed and use it immediately. Pigs at different stages require different corn grind sizes: finer for piglets and coarser for finishing pigs. The grinder should be easy to adjust. Don’t prepare too much homemade feed at once; use it up the same day whenever possible to keep it fresh and prevent it from becoming damp and moldy after preparation.
Four. What should I do if I already have diarrhea or have been poisoned?
If the pigs have already developed diarrhea or are passing feed undigested after being fed new-crop corn, stop feeding it immediately or greatly reduce the amount, and switch back to the ration containing old-crop corn. Don’t try to push through and keep feeding it.
Afterward, add probiotics and acidifiers to the feed or drinking water to regulate the gut and help restore the gut flora; bile acid products may also be used to help the liver detoxify and promote nutrient absorption. During diarrhea, make sure to supplement electrolytes, multivitamins, and oral rehydration salts to prevent dehydration.
If sows develop vulvar redness and swelling or false estrus, or pigs show obvious signs of poisoning such as jaundice or neurological symptoms, the toxins have already caused harm. Replace the raw material immediately, have a licensed veterinarian assess the situation on site, and submit the remaining corn for testing. Do not try to handle it yourself based on experience.
In closing
New corn is inexpensive and fresh, and using it well can indeed reduce costs, but it has its own “post-ripening” process. There’s no need to rush.
Keep moisture under control, allow enough time for aging, make the transition from old corn to new corn gradually, and stay on top of mold removal and enzyme preparations. If these steps are done properly, feeding pigs new corn should not cause major problems. In pig farming, the feed itself is often not the problem; it is using it too soon. Let the grain “wake up” fully, and the pigs will grow more steadily.
But after just a few days, problems arise: the pigs develop diarrhea, with undigested corn kernels in their feces. They eat plenty but show no weight gain; some eat less or vomit, while sows develop swollen, red vulvas and come into heat irregularly. Instead of saving money, they end up losing it.
New corn is a good feed ingredient, but freshly harvested corn really should not be fed to pigs directly. Today, we’ll explain what you need to know. Follow these steps, and you can still raise healthy pigs with new corn.
Corn drying after the autumn harvest
I. The “temperament” of new corn: it has not fully “ripened” yet
Many people think that once corn has been dried, it is ready. In fact, corn is a crop that continues to mature after harvest and needs to undergo “secondary maturation.”
In freshly harvested corn, most of the starch is resistant starch, also called macromolecular polysaccharides. This starch is highly viscous and difficult to digest. Enzymes in a pig’s small intestine have difficulty breaking it down, so it cannot be absorbed after ingestion. The corn needs to be stored in a well-ventilated, dry warehouse for a period of time before the resistant starch gradually converts into normal starch that pigs can absorb and use. This process generally takes 5 to 6 weeks, or about a month and a half.
That is why pigs fed a lot of new corn grow slowly: the energy is not absorbed and is all excreted in the feces.
Fresh corn also has a high moisture content. The safe moisture content for corn used in feed is generally required to be below 14%, but newly harvested corn typically has a moisture content of 15% to 20% in North China, and 20% to 30% in Northeast China and Inner Mongolia. High moisture content dilutes the energy, disrupts nutritional balance, and makes the corn particularly prone to heating and mold.
II. Three common pitfalls when feeding pigs new corn
Pit one: diarrhea and undigested feed
This is the most typical presentation. The feces are loose and unformed, with whole or broken corn kernels visible in them. In the industry, this is called “feed passage.” The root cause is resistant starch and high moisture content. Indigestible starch enters the hindgut and ferments; at the same time, the energy in the diet is diluted and the protein proportion rises relatively. Pigs cannot digest it, resulting in nutritional diarrhea. Piglets’ intestines are not yet fully developed, so they show the most pronounced reaction, and often the entire litter develops diarrhea.
Pitfall two: Mycotoxins, the invisible pitfall
Newly harvested corn has high moisture content and strong respiration, and threshing inevitably produces some broken kernels, making it prone to heating and mold during storage. A special reminder: mold does not grow only in storage facilities; corn may already be contaminated while growing in the field. About one quarter of corn has been contaminated by mold around the time of harvest.
There are three common types of toxins, each of which harms a different area:
·Aflatoxin: damages the liver and suppresses immunity, lowering pigs’ resistance and making them more susceptible to illness; severe cases can be fatal.
·Vomiting toxin (DON): Pigs may refuse feed, reduce their feed intake, or even vomit, which is a major reason their feed intake fails to increase.
·Zearalenone: harms reproduction, causing swelling of the vulva, false estrus, and repeated failure to conceive in sows. Replacement gilts are particularly at risk.
As for toxins, corn can look perfectly fine and still exceed the limit; you can’t sort them out just by looking.
Pitfall three: High feed intake, a high feed-to-meat ratio, and slow growth
New corn has a low actual energy value. Pigs may eat more to make up for the energy shortfall, but they cannot absorb what they eat. As a result, feed intake increases, daily weight gain does not, and the feed-to-meat ratio actually rises. When you do the math, using cheaper new corn may result in higher pig-raising costs.
Here’s a counterintuitive point: during the new-corn phase, never try to make up for energy by adding extra fat. Fat can worsen diarrhea, defeating the purpose.
Three. How should you use new corn? Remember the five steps
New corn can be used; it just needs to be used the right way. The core approach comes down to nine Chinese characters: control moisture, allow it to age, and transition steadily.
Step one, sun-dry or heat-dry until the moisture content is below 14%. After harvesting, dry the crop in the sun or with heat as soon as possible. It is best to check the moisture content before storage and use, keeping it within 14%. Do not let the drying temperature exceed 60℃. Excessive heat can denature starch and damage vitamins, which can impair digestion.
Step two: Allow it to mature fully, and leave it for one and a half months. After drying, winnowing, and removing impurities by sifting, put it into storage in a cool, ventilated, dry place for 5–6 weeks. Use it once the resistant starch has been almost fully converted. This is the easiest and most effective method. Keep the warehouse temperature below 24℃ and the relative humidity below 80%.
Step three: If you need to use it urgently, mix new and old corn and transition gradually. If you can't wait a month and a half, feed a mixture of new corn and high-quality old corn, gradually increasing the proportion of new corn and extending the transition period to more than a month. You can follow this schedule: feed new and old corn at a ratio of 4:1 for half a month, then 3:1 for half a month, then 2:1 for half a month, and only then switch completely to new corn. Never switch everything at once; the pigs' intestines and gut flora won't be able to handle it. Monitor their stools closely while changing feed. If they develop diarrhea, immediately reduce the amount or stop feeding it.
Step four: Winnow and sieve, then add a mold inhibitor and enzyme preparation. Before use, sieve and winnow the grain to remove as many broken kernels, impurities, and moldy kernels as possible. Add a mycotoxin binder to the complete feed (such as montmorillonite or yeast cell wall products; generally, add 1–2 kilograms per ton of feed, following the product instructions). To address resistant starch, add a compound enzyme containing amylase and glucoamylase to help break it down. Pay particular attention to controlling zearalenone in sow and gilt feed. If possible, have new corn tested for toxins before use.
Step five: Don’t grind the feed too finely; prepare homemade feed as needed and use it immediately. Pigs at different stages require different corn grind sizes: finer for piglets and coarser for finishing pigs. The grinder should be easy to adjust. Don’t prepare too much homemade feed at once; use it up the same day whenever possible to keep it fresh and prevent it from becoming damp and moldy after preparation.
Four. What should I do if I already have diarrhea or have been poisoned?
If the pigs have already developed diarrhea or are passing feed undigested after being fed new-crop corn, stop feeding it immediately or greatly reduce the amount, and switch back to the ration containing old-crop corn. Don’t try to push through and keep feeding it.
Afterward, add probiotics and acidifiers to the feed or drinking water to regulate the gut and help restore the gut flora; bile acid products may also be used to help the liver detoxify and promote nutrient absorption. During diarrhea, make sure to supplement electrolytes, multivitamins, and oral rehydration salts to prevent dehydration.
If sows develop vulvar redness and swelling or false estrus, or pigs show obvious signs of poisoning such as jaundice or neurological symptoms, the toxins have already caused harm. Replace the raw material immediately, have a licensed veterinarian assess the situation on site, and submit the remaining corn for testing. Do not try to handle it yourself based on experience.
In closing
New corn is inexpensive and fresh, and using it well can indeed reduce costs, but it has its own “post-ripening” process. There’s no need to rush.
Keep moisture under control, allow enough time for aging, make the transition from old corn to new corn gradually, and stay on top of mold removal and enzyme preparations. If these steps are done properly, feeding pigs new corn should not cause major problems. In pig farming, the feed itself is often not the problem; it is using it too soon. Let the grain “wake up” fully, and the pigs will grow more steadily.