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Impact of Rain on Hay Quality

Forage in swath. Photo credit: Barry Yaremcio

In some areas, the long dry spells have been replaced with showers every two to three days. Not enough time for hay or greenfeed to be baled without being rained on. Rain impacts forage quality and nutrient availability of the forage.

Rain shortly after cutting reactivates respiration when plant moisture is above 50%. Plant sugars are used to keep the plants alive. Quality is lost. If rain is received later in the drying cycle, when plants have less than 40% moisture; the cell walls in the plant have ruptured. Soluble sugars, soluble protein, and vitamin precursors leach out the cells resulting in a loss in quality. These are highly nutritious components in forage. Fibre levels increase in relation to what remains in the forage.

If swaths remain wet for an extended period, moulds can form. Most moulds are nuisances, but all impact quality. A general caution is that red, green, pink, and blue moulds could contain mycotoxins. Samples should be tested before feeding the forage to animals.

Rain damaged hay contains more acid detergent fibre (ADF) and neutral detergent fibre (NDF) than hay that is not rained on due to the loss of the soluble components. Fibre levels can increase by as much as 10 percentage points depending on the length and intensity of the rain. NDF is a feed component that is difficult for animals to digest. Feed passage rates are slowed with higher NDF concentrations resulting in lower voluntary feed intake.

Forage digestibility is also reduced in rain damaged hay. Animals cannot extract nutrients as efficiently from hay that is rained on compared to undamaged hay.

To prevent weather damage, one option is to make chopped or round bale silage. Costs and manpower requirements are higher, but this strategy results in higher yields because leaf loss is reduced. With higher leaf retention, quality is higher than dry hay off the same field.

For additional information on the impact of rain or showers on hay quality, contact Barry at 403-741-6032 or bjyaremcio@gmailcom.


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