What are the risks associated with feeding high level of potassium in hay to bred heifers? #255271 - Ask Extension


What are the risks associated with feeding high level of potassium in hay to bred heifers? #255271

Asked June 18, 2015, 4:27 PM EDT

Are there any special precautions I should take or anything to watch out for when feeding hay this winter that has a 2.5-3% potassium content other than switching to a high magnesium mineral? I had planned to feed this hay to bred heifers and have it account for 95-100% of their daily DM intake.

Newberry County South Carolina

Expert Response


Are you feeding this hay to Beef or Dairy Heifers???  Please email me at cmartel@vt.edu
Cynthia Martel Replied July 06, 2015, 9:08 AM EDT
Beef cattle, bred heifers & first calf cows.
The Question Asker Replied July 06, 2015, 9:11 AM EDT
You need to be aware of Winter Tetany.  Your cows can still get Tetany in the winter time if the levels of Potassium are to high for the body to metablize.  Remember high levels of  Potassium can cause a Magnesium deficiency.  Magnesium is critical mineral for the nervous system.  What did your hay samples test for in Magnesium??  A mineral analysis showing less than 0.15% magnesium in hay in considered low.  Potassium is also crucial for many metabolic systems in the body, but excess potassium is readily excreted in the urine. One research article will claim 3% potassium is the max. tolerable level.  But others will claim 6% potassium has been added to the diet of non-lactating animals with no toxicity symptoms.

Are you feeding anything else with the hay??? 

Need to test hay to see how bad the imbalance of magnesium, potassium, and calcium is. 

If feeding a mineral supplement - check to see the level of Potassium in the mineral pack is, remember with high levels in the hay and more in the mineral you only create more of a problem.

You could consider feeding a hay higher in calcium and magnesium with the hay that is low in magnesium to help off set the Potassium levels.  

Watch out Alfalfa can be high in potassium.

Research has shown that higher levels of Potassium have more of a negative effect on lactating females than on non-lactating.  However the high levels and the high percent in the diet could make it more readily available to the animal.

You best precaution is to either add magnesium mineral or find a hay source lower in potassium to help balance the levels out.  

Is this your only hay source - I am guessing they are round bales that will be fed free choice, correct??

Cynthia Martel Replied July 07, 2015, 10:12 AM EDT
I'm in the Southeast, so alfalfa isn't an affordable option. All stats are 100% DM, tested 5 different batches, all about equal # of bales, this makes about 60% of the hay that I will feed this winter in total, waiting for rain to make some more. K ranges from 2.20% - 3.05% Ca ranges from 0.37%-0.63% Mg ranges from 0.22%-0.28% If I'm understanding you correctly, if I feed the 3.05% K, 0.24% Mg, 0.55% Ca hay primarily to heifers, that should mitigate most of the issues with excess K. That batch of hay tested out at 19% crude protein and 64% TDN, so I'm probably going to have to rotate with lower quality hay anyway as they get close to calving to keep the heifers from getting too fat. It's my highest quality hay, and I was planning to feed it to the first calvers, but that now seems like a risk I'm not willing to take. The other 75% of my hay tested at 2.5% K or lower, so I'll plan to feed the next best hay I've got (16% crude protein, 61% TDN, 2.5% K, 0.25% Mg, 0.62% Ca), to the first calvers, and have to supplement them with something else. I'm kind of new to testing the hay and formulating a ration based on dietary requirements, and I just got worried when I got those results. Thanks for answering!
The Question Asker Replied July 07, 2015, 11:17 AM EDT

Have you had your soil tested???  Get  a soil test and see if you can help reduce Potassium.  You may need to add Calcium (lime) to your soil.  Check with your local extension agent to see if they can help you collect soil samples and get it tested for free.  Here in VA producers can get soil sample testing for free at Virginia Tech.
Cynthia Martel Replied July 20, 2015, 3:40 PM EDT
We do soil testing every other year. In SC Clemson does the testing for $6. However, this hay was purchased. I will recommend the hay producer get his soil tested. 
The Question Asker Replied July 20, 2015, 3:49 PM EDT
Ok.  I would start there.  Just try to dilute (mix) hay as much as you can to help reduce high levels on the animals. 
Cynthia Martel Replied July 20, 2015, 3:53 PM EDT
The Question Asker Replied July 20, 2015, 3:58 PM EDT

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