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Maintain forage fibre in a dairy diet

Dairy Corner with Peter Vitti

I recently visited a dairy producer running 200 cows having problems maintaining butterfat at 3.9 per cent in his 35-kg milk producing herd. He asked me to walk the lactation barn and see what I could find out.

It took about 20 minutes to walk the feed bunk and cows, and in the end, I suspected that he was feeding a TMR that contained not enough effective forage fibre, too much soluble protein, and silage that was cut too fine. I confirmed my findings with a practical test of the TMR and wrote out a list of corrective actions to maintain/increase milk and milkfat production.

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beef on a winter pasture

The specific lack of effective forage fibre was a common theme throughout this lactation barn. Unlike energy and protein, effective forage fibre is not a true nutrient, but there is a requirement for it in the dairy cow’s diet. Its main job is to maintain a healthy population of rumen microbes, which in turn drives optimum feed fermentation, digestion, essential nutrient absorption and normal gut mobility.

As a dairy nutritionist, I advocate good cud-chewing (first shaded area) is the first vital part of this natural process. It simply keeps the cow’s digestive system in good working order.

Literarily at the end of lactating dairy cows, I looked at their manure (second shaded area). Its consistency tells me a lot of information about the ingredient profile of their lactation diet as well as how it was ultimately digested. Manure that is produced by cows consuming a well-balanced ration with adequate effective forage fibre is very uniform and should have the consistency of porridge.

Because a significant number of these dairy cows had loose manure, it was a warning sign to me that inadequate dietary fibre was being fed or some other feed ingredient was speeding up its rate of gut passage. Such rapid passing feed cannot be adequately digested for essential nutrients to make milk or milk fat.

Last, I took a handful of TMR (third shaded area) and linked it together to the signals from what I saw from the cows: a lack of effective forage fibre. It smelled good, had a good moisture-feel to it, was consistent in the bunk, but it also lacked; the recommended 15 to 20 per cent dietary forage fibre over one- to 1-1/2-inch long-stem forages. Furthermore, this lactating diet had lots of second-cut alfalfa silage that could be a source of high soluble protein levels that often increase unwarranted rates of feed passage.

Before I left the barn, I did a “quick” test on the amount of effective forage fibre provided in this diet. I put a sample of the diet in a bucket filled with warm water. The point of this test is to mimic the natural floating mat of dairy diet in the rumen. If only about 20 per cent of the ration floats onto of the water; there should be enough effective forage fibre in the diet.

Unfortunately, most of this dairy diet sunk to the bottom of the bucket. Therefore, I made the following corrective actions for rebalancing effective forage fibre in this diet:

  1. 28 per cent NDF is assured in the TMR with 75 per cent of this NDF coming from forage sources. Note: palm fat remained at 300 grams per head, daily.
  2. Replace 25 per cent of second-cut alfalfa silage with barley silage and mixed first cut alfalfa/grass silage. Increase dried distillers’ grains by 1.5 lbs. to increase dietary bypass protein levels.
  3. Add two pounds of long-stem grass hay replacing equivalent high-protein second-cut alfalfa silage.

One month after this lactation diet was rebalanced, the increased amount of effective forage fibre in this case seem to build a good “rumen mat” in this herd. Milk yield remained and milkfat increased by 0.2 per cent. That happened six months ago. Now, I understand a significant number of fresh cows have been added and changed the dynamics of the herd. Milkfat percentage is slightly down, but this time around, effective forage fibre in the diet remains adequate.

About the author

Columnist

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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