Would a little Potassium Boost your Cow’s Milk Fat?
There are numerous dietary factors that can result in milk fat depression in the dairy cow. The common factors are tool little forage, rapidly degraded starch in the rumen, and too much fat or free fatty acids. Each of these has a role in negatively affecting the rumen environment. Once these dietary management factors are corrected the milk fat usually returns to normal.
What about the cow that seemingly has a normal fat test, say a 4.0 % milk fat? Are there any dietary management options to improve fat production in cows that would appear to have a normal fat test?
We have been studying the role of dietary cation-anion (DCAD) balance in early lactation on efficiency of milk production and have observed that cows that have a normal fat test can benefit from supplemental K in the form of potassium carbonate sesquihydrate. We fed two groups of high producing early lactation cows diets differing only in the amount of potassium (as potassium carbonate sesquihydrate). Dietary levels of K and DCAD were 1.3 and 2.1 % of DM, and 32 and 53 mEq/100 g DM for control and supplemented cows, respectively.
Energy corrected milk and 3.5% FCM was significantly greater for K supplemented cows (linear contrast) indicating greater persistency of corrected milk production with an average increase in ECM of about 6.6 lb and FCM of about 8.8 lb. Milk fat % increased from 4.01 to 4.38.
As a result of collaborative relationship with Clemson University, we may have an explanation for the increased milk fat test. There appears to be two pathways for dietary linoleic acid (C 18:2 ) to be bio-hydrogenated to stearic acid (C 18:0) in the rumen (see figure). The intermediate trans fatty acids in the biohydrogenation process are the fatty acids of interest. The preferred pathway is the top portion of the figure. Trans fatty acids have been shown to be very potent in small amounts and to have a negative effect on the mammary gland by reducing milk fat production. A common name for these fatty acids is conjugated linoleic acid or CLAs. The Clemson research team has demonstrated with rumen fermenters that potassium carbonate sesquihydrate can reduce the amount of “bad” trans fatty acids. We looked at the fatty acid profile in milk fat of the cows fed in the WSU trial and confirmed lower amounts of the key CLAs.
Joe Harrison, Livestock Nutrient Management Specialist Tom Jenkins, Professor Emeritus, Clemson University