Potassium is often associated with alleviating heat stress, but we’re learning that potassium balance matters more than we realized.
By Dr. Elliot Block, Senior Manager, Technology, Arm & Hammer Animal Nutrition
Dietary potassium is a significant nutrient for good dairy cow health and nutrition. This macromineral impacts carbohydrate metabolism, amino acid uptake and protein synthesis, all of which aid in milk production as well as reproductive performance, immune function and cow wellbeing. While it’s important that prefresh cows not receive too much potassium, cows in early lactation benefit from a boost in dietary potassium levels.
New research1 published in the October 2012 issue of Professional Animal Scientist indicates that fresh cows are often deficient in potassium, especially for the first 10 weeks of lactation. But the deficiency can also persist longer, and can occur even when cows are fed dietary potassium at NRC-recommended levels.
Potassium is often associated with alleviating the effects of heat stress, but we’re learning that potassium balance matters more than we realized and it is something that should be monitored and accounted for throughout the year.
What’s the Point?
Cows lose a significant amount of potassium through the normal, everyday function of producing milk, and this nutrient must be replaced through the diet to maintain and improve production.
This is important to take into consideration because potassium ions participate in many essential biological processes, such as the maintenance of osmotic potential within cells; nerve impulse transmission; enzyme reactions in cellular metabolism; cardiac, skeletal and smooth muscle function; and the maintenance of normal kidney function.2
Potassium’s role is also tied to the concept of dietary cation anion difference (DCAD). Potassium is a cation that raises DCAD, which represents interaction among the macrominerals of sodium, potassium, chloride and sulfur. Ideally, DCAD levels should be +35 to +45 meq/100g for cows in early lactation.
Supplemental Potassium Needed
Cows respond positively to supplemental potassium in the diet.
Research3 conducted at the University of Washington in 2008 showed that increasing the level of dietary potassium in the early lactation diet resulted in an increase in production of milk, 3.5% fat corrected milk and milk fat. This increase was not associated with an increase in dry matter intake, and therefore appears to be unrelated to energy intake.
Also, the added dietary potassium carbonate decreased undesirable unsaturated and trans-fatty acids, and increased C18:0 (stearic acid) in milk. (Click here for more on this research.) [link to October 2012 WSU article “Would a little potassium boost your cow’s milk fat?]
The research, published in the October Professional Animal Scientist, adds further support for increasing early lactation dietary potassium. It shows cows fed a diet with 1.4% potassium were deficient in potassium through the first 20 weeks of lactation—but most significantly in the first 10 weeks of lactation.
Two possible explanations exist for this deficiency3:
• First, because early lactation cows generally eat less than mid-lactation cows, there is a need to increase nutrient concentrations to reflect reduced feed intakes.
• Second, most previous macro-mineral research was conducted with low and medium producing cows; high-producing cows secrete more of these minerals in milk and generate more acid in the rumen and blood.
However, regardless of the reason why, it’s becoming apparent that most early lactation cows need more dietary potassium. To bring a cow into potassium balance, diets need to be supplemented with additional potassium. Total dietary potassium should be a minimum of 1.7%.
Given market conditions, it’s important for producers to capture the greatest milk price possible. Since it’s been repeatedly shown that potassium can have a positive impact on milk fat production, proper potassium supplementation—especially during early lactation—can help achieve increased levels of milk fat production and potentially improve profitability.
1 Jarrett 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.
2 Sanchez B. Potassium and Other Macrominerals for the Lactating Dairy Cow. Western Canadian Dairy Seminar. Advances in Dairy Technology 2000;12:127-140.
3 Harrison J. Potassium in the Early Lactation Dairy Cow and its Impact on Milk and Milk Fat Production. Western Canadian Dairy Seminar. Advances in Dairy Technology 2011;23:313-319. Available at: http://www.wcds.ca/proc/2011/Manuscripts/Harrison2.pdf. Accessed November 27, 2012.