How Rain Takes Toll on Forage Quality

The challenge of making hay between the raindrops in an unusually wet summer can certainly raise producer frustration levels at times. It also changes the crop's nutrient and feeding value.

Rain delayed alfalfa harvest on farms may result in the following due to advanced maturity of alfalfa-type hay:

  • higher Neutral Detergent Fibre (NDF) values (about 0.9 per cent increase per day of delayed harvesting);
  • higher Acid Detergent Fibre (ADF) values (about 0.7 per cent increase per day and more lignin);
  • decreased protein (about 0.5 per cent per day);
  • decreased calcium due to maturity and heavier grass content; If hay got rained on here are some other physical changes:
  • increased leaf loss due to physical damage (leaves are high in protein and low in fibre);
  • increased breakdown of protein to non-protein nitrogen (the breakdown rate is rapid when moisture levels are above 60 per cent);
  • decreased soluble carbohydrate levels lowering the fermentation rate;
  • water-soluble minerals washed out;
  • dry matter yields dropping 30 to 50 per cent;
  • increased fibre levels.

In just five or six days hay can go from ideal alfalfa of 20 per cent crude protein, 30 per cent ADF and 40 per cent NDF to 17, 34 and 45, respectively. Once lower quality forage is harvested, the only option is to feed it. This necessitates adjusting feeding and management. Below is a checklist:

  • Test all forages before feeding and balance rations more often.
  • Check hays and fermented silages for heat damage.
  • Know where you have stored feeds of different quality. Keep the highest quality forage for high-producing, early-lactation cows, or seasons of the year when more cows are fresh.
  • Feed 15 to 25 per cent more volume than if hay is of poorer quality. Let cows sort through it and pick out the best parts.
  • If using a total mixed ration with an adjustable chop length, chop hay a little finer to increase intake and digestibility. Make sure to still have effective fibre length.
  • Feed more corn silage or high-fibre ingredients such as soy hulls, beet pulp, brewers' grains or cottonseed.
  • Plan to purchase more protein. Look at alternatives such as distiller's grains, corn gluten meal, canola meal or possibly raw soybeans.
  • Ammoniate your corn silage to increase the source of readily available protein.
  • Adjust the type or amount of mineral mix to account for lower calcium levels.
  • Watch for moldy feeds or mycotoxin formation. If in doubt leave it out.
  • Consider a two-TMR group system. Use poorer quality forages in the lower production TMR.
  • Feed yeast or yeast culture to increase the number or cellulose-digesting bacteria in the rumen.

The challenge of feeding poor quality forages requires closer management and fine-tuning.

This article appeared in the November 2008 Ruminations column of the Ontario Milk Producer magazine.

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