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Balance “pineapple” corn silage into dairy diets

Corn with rolled leaves should definitely be tested for nitrates

Curled leaves on corn plants due to drought cause it look a bit like the spears of a pineapple crop, resulting in what some call pineapple corn.

I never noticed a "pineapple" cornfield until I ‘ve seen several of them in Manitoba this summer. As I have done, dairy producers should take them in stride as part of our ongoing drought. 

A pineapple cornfield is simply what happens to a corn plant after months of severe drought. (It is a term used by writer Emily Unglesbee in a DTN article June 6, 2021). Despite its natural means of water conservation (i.e.: leaf-holes called stomates - close under dry conditions), there is still considerable water loss, coupled with its roots, which are not absorbing enough water. As a result, the inside water pressure of the plants drops, which causes the corn leaves to curl. Coupled with a lack of corncob development and general height to whole corn plants; makes it look like a pineapple crop. 

The funny thing about a pineapple cornfield is research shows that once it is ensiled, its fermented bio-mass contains about 85 - 95 per cent of the overall nutrition of normal corn silage, despite much lower tonnage per acre, due to drought. A typical area-survey of drought-stressed corn silage has shown: one to two per cent more protein, about 95 per cent of the overall energy of lactation (Nel) and high NDF digestibility compared to good corn silage. 

Difference of opinion

Other dairy science is less favorable about drought corn silage. Some nutritionists point out that it might contain good dietary energy, but it often misses about 25 – 30 per cent of its starch content, which underlies good milk production. Furthermore, drought corn silage is notorious for harboring toxic nitrate levels, despite a 70 per cent reduction of nitrate-nitrogen levels due to the fermentation process from original pre-ensiled corn-plants levels. For example, I knew one producer who lost several replacement heifers, because a major portion of their diet was largely made up of high-nitrate corn silage.

Another producer fed untested drought-stressed corn silage to his lactation dairy herd, a few years ago. Soon after it was fed, it led to several digestive upsets and irreversible liver damage among the lactation herd. Plus, he could not get a single milking cow - pregnant for an entire six-week period. It was later discovered by his vet that his drought corn silage contained toxic mycotoxin levels of poisonous aflatoxins.

These are two good reasons to test pineapple silage for nitrates and mold/mycotoxin (aflatoxin) screen tests, particularly when opening up the bunk or silo. I would also advise that “before” ensiled samples be sent away for a moisture test in order to take the best opportunity to put up drought silage in the best possible moisture-condition. 

Optimum corn silage fermentation occurs when whole plant moisture is between 65 – 70 per cent. This the standard recommendation for making corn silage in horizontal bags and bunker silos, with a slight drier allowance in tall tower silos. Once these structures are opened-up (along with pending nitrate and mycotoxin tests); I would test fermented corn silage samples - again for moisture as well as now nutrient values: crude protein, soluble and UIP protein, ADIN (heat-damaged protein), NDF, 30-hour NDF digestibility, NFC and dietary starch levels. 

As a dairy nutritionist, I am now ready to balance a lactation dairy diet (40 litres milk, 4.0 per cent milkfat, DIM = 160), which would not stray too far from a conventional diet formulated with “normal” corn silage. However, I would emphasis the following points in my feeding program: 

  1. Moisture – Make sure that the moisture content was 50 – 55 per cent moisture. Add water to a dry TMR or more dry hay to a wet TMR. 
  2. Effective-fiber – Meet a 28 per cent NDF level (with 75 per cent coming from forage sources) to promote good rumination. 
  3. NFC and starch level – Limit NFC to 38 per cent of the diet, yet add back lost starch from ground corn or barley. 
  4. Add liquid molasses – I have a dairy friend that successfully feeds four lbs. of molasses as rapid energy, whenever to compensate for a loss of starch in his dairy lactation diet. 
  5. Bypass fat – No more than 450 g of palm fat should be fed.

Case-in-point – I have a dairy producer (200 dairy cows), whom has a 500-acres field of pineapple corn. He plans to send away the appropriate samples to an accredited laboratory to make sure his pineapple corn silage is safe to feed as well as conduct an above nutrient profile. Once we get the results back, I will reformulate this lactating dairy diet as if it were any other type of corn silage. 

About the author


Peter Vitti is an independent livestock nutritionist and consultant based in Winnipeg. To reach him call 204-254-7497 or by email at [email protected]



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