Arm & Hammer Animal and Food Production

Cool the Effects of Heat Stress

The calendar may say March, but it’s not too early to be thinking about heat stress and making necessary adjustments to manage its effects on your herd.

Plan now to prevent the higher temperatures that are just around the corner from sinking production goals. Just as you should give your cooling equipment a preseason tune-up, you must do the same for your nutrition strategy.

Ensuring that your ration is formulated to contain supplemental dietary potassium provided by a stabilized potassium carbonate source is an excellent place to start.


That’s because hot weather reduces feed intake and rumination, dragging down performance. This condition is often made worse because cows are prone to potassium deficiencies during heat stress.

Potassium—especially during period of heat stress—is a key dietary consideration because: 

  • Potassium is the #1 mineral1 in milk, even higher than calcium. Yet, potassium is the main component of sweat, and cows lose it quickly through urination and increased perspiration during heat stress. It’s imperative that you replace what is lost.
  • Fresh cows especially require higher levels of dietary potassium. Research2 shows that cows are often potassium deficient for the first 10 weeks of lactation even when potassium is fed at National Research Council levels.
  • University research3 shows increasing dietary potassium levels boosted fat-corrected milk production as much as 8.5 pounds per day.

Protect your herd and potential profits by preventing potassium deficiencies. Manage high production and fresh cow diets to include 1.7% to 2% potassium to help maximize production and improve cow starts during heat stress this summer.

Buffers and Other considerations

Buffers help stabilize rumen acids, increasing feed intake and improving rumen performance for enhanced productivity. Cows need this assistance throughout the year, but especially during periods of heat stress.

Today’s diets include more fermentable carbohydrates—which require more buffering, not less. Rations also minimize fiber (physically effective NDF) and rely more on microbial protein and fermentation than in the past. In addition, variation in feed ingredient quality plays a significant role in ration performance.


The key is to feed buffers at recommended levels and buck the unfortunate downward trend in ration buffer inclusion rates. To increase animal success, the recommended inclusion rate for sodium bicarbonate is 0.75% to 1.0% of TMR dry matter.4

Also consider:

  • Altering feeding times to deliver feed during the coolest part of the day
  • If practical, increase the number of daily feeding times (by mixing smaller loads) to keep feed in the bunk cool
  • Research5 also indicates that increasing the dietary cation-anion difference (DCAD) for lactating cows increased milk yield when sodium (sodium bicarbonate) and potassium (potassium carbonate) were added to the diet.
  • Avoid excessive concentrations of dietary sulfate and chloride in lactating cow diets especially during heat stress.
  • Lastly, be sure that rations include proper levels of yeast culture. Research6 in California found that feeding yeast culture improved daily milk yield by 2.6 pounds per cow during heat-stressed conditions.

To learn more, visit

1 University of Illinois Department of Animal Science. Milk Composition Minerals. Available at: Accessed February 4, 2016.

2Jarrett JP, Taylor MS, Nennich TD, Knowlton KF, Harrison J, Block E. Effect of dietary calcium and stage of lactation on potassium balance in lactating Holstein cows through 20 weeks of lactation. The Professional Animal Scientist 2012;28:502-506.

3 White R, Harrison J, Kincaid R, Block E, St-Pierre N. Effectiveness of potassium bicarbonate to increase dietary cation-anion difference in early lactation cows. J Anim Sci Vol. 86, E-Suppl. 2/J Dairy Sci 2008;91.

4 Shaver RD. Feed Delivery and Bunk Management Aspects of Laminitis in Dairy Herds Fed Total Mixed Rations. University of Wisconsin – Madison. Available at: Accessed February 19, 2016.

5 Litherland NB, Sawall Z. Nutrition adjustments for heat stressed dairy cows. University of Minnesota Extension. Available at: Accessed March 4, 2016.

6 Bruno R, Santos JEP, Rutieliano H, Cerri R, Robinson P. The effect of feeding A-MAX Yeast Culture on performance of high-producing dairy cows in summer heat stress. Animal Feed Science and Technology 2009;150:175-186. University of California-Davis. Research Bulletin 3.

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