By Dr. Dave Jones, Ph.D., P.A.S.
Fatty acids are components of lipid molecules most commonly stored in the form of a triglyceride (1 glycerol, 3 fatty acids). The nutritionally important component of fats are the fatty acids and they serve many different functions:
– Source of energy
– Affect breeding proficiency
– Modulators of the immune system
– Building blocks for milk fat and other lipids in the body
There are two basic types of fatty acids, saturated and unsaturated. Saturated fats are given this name because they are saturated with hydrogen ions and contain no double bonds. The lack of double bonds gives a saturated fat a higher melting point and, therefore, likely to be solid at room temperature. Unsaturated fats have 1 or more double bonds (not saturated with hydrogen ions) giving them a lower melting point creating a liquid (oil) at room temperature. Fatty acids are typically represented in numerical form which is relatively easy to follow. For example, 18:2 n-6 represents a fatty acid with 18 carbons, 2 double bonds (unsaturated), and the first double bond starts 6 carbons from the methyl end of the fatty acid. Biohydrogenation of unsaturated fatty acids to saturated fatty acids in the rumen is an important process that will not be discussed in this article. The effect of oils on the rumen has been discussed in other Agri-King Advantage and Viewpoint articles (see references).
Recent work from Michigan State University has explored combinations of three fatty acids with some interesting results. These fatty acids include:
– Palmitic Acid (16:0)
– Stearic Acid (18:0)
– Oleic acid (18:1 n-9)
This work has created a ‘buzz’ in the industry with nutritionists trying to feed fat supplements to generate some specific fatty acid ratios. It is important to note, everything we will discuss moving forward pertains to rumen inert fat sources (rumen bypass fat).
It has been recognized that feeding palmitic acid (PA) to dairy cows can help increase milk fat (Figure 1. de Souza and Lock, 2018). This occurs because palmitic acid, when fed in the diet, can go directly to the mammary gland as a source of milk fatty acids. Remember, palmitic acid is a saturated fat that escapes the rumen untouched and is available to the cow in its original dietary form.
The milk fatty acid effect of palmitic acid lead to the question “is there an ideal ratio of dietary fatty acids for the dairy cow.” Work out of Michigan State University demonstrated the following (against a no fat control) when various percentages of palmitic acid, stearic acid, and oleic acid (80% palmitic; 40% palmitic:40% stearic; 45% palmitic:35% oleic) were fed (de Souza et al., 2018.):
1) Palmitic acid fed at 80% increased the digestibility of NDF, total fatty acids, 16 carbon fatty acids and 18 carbon fatty acids.
2) Palmitic acid fed at 80% showed the best energy corrected milk (likely due to increased milk fat).
3) When stearic acid was fed with palmitic acid (40%/40% blend) the digestibility of NDF, total fatty acids, 16 carbon fatty acids, and 18 carbon fatty acids were reduced below that of the control. Stearic acid had a negative effect on digestibility.
4) The digestibility of NDF, total fatty acids, 16 carbon fatty acids, and 18 carbon fatty acids were restored when oleic acid replace stearic acid (45% palmitic acid and 35% oleic acid).
The responses seen with palmitic acid and oleic acid lead researchers to further investigate if there is an ideal ratio between these two fatty acids. Four different ratios of palmitic acid to oleic acid (80:10, 77:13, 66:24 and 60:30) were studied across high and low producing cows. The following results were observed:
1) Energy corrected milk reduced for low producing cows as palmitic acid went from 80% of the fatty acid blend to 60% (Figure 2. de Souza et al., 2019). This result is likely due to the higher palmitic acid (80%) leading to higher milk fat concentration. This effect was reduced when palmitic acid was lowered to 60% of the blend.
2) Energy corrected milk increased for high producing cows as palmitic acid went from 80% of the fatty acid blend to 60% (oleic acid was increased in the blend) (Figure 2. de Souza et al., 2019). This result is likely due to increased DM and fatty acid digestibility as palmitic acid was reduced from 80% to 60% with the addition of oleic acid.
3) Fresh cows fed the 80:10 ratio of palmitic acid to oleic acid showed greater energy corrected milk and greater body condition loss, compared with controls, when fed to post fresh cows (de Souza and Lock, 2019). Higher energy corrected milk, during a time of negative energy balance, directed the cows fed the 80:10 blend to pull more body fat reserves.
The results demonstrate, although preliminary, that the ratio of palmitic acid and oleic acid in the diet can have differing results on low and high producing cows. If fresh cows are fed a diet to support more energy corrected milk (at a time of negative energy balance) the cows can lose more body weight to support the production. This tells us that total energy of the diet should not be overlooked when considering fatty acid ratios.
Further research from Michigan State University demonstrates that abomasal infusion of emulsifiers helps with the absorption of fatty acids in the GI tract (Figure 3. Lock, 2019). This is quite important because fatty acids cannot be utilized for energy, or any other function, if they are not absorbed across the epithelial layer of the intestines. Recently, Agri-King updated Ru-Mend and Zy-Mend with technology that provides emulsifiers to the intestine of the dairy cow to assist with fatty acid absorption. This works alongside previous technology in these two products that assists with non-fatty acid nutrient absorption. Therefore, it is recommended that Ru-Mend or Zy-Mend (follow Agri-King feeding guidelines) be fed in diets attempting to supplement fatty acids with rumen inert fat/fatty acid products to assist with fatty acid absorption.
Contact your Agri-King representative to investigate how supplemental fat/fatty acids and Ru-Mend/Zy-Mend technologies can be used on your operation. AK
Koch, L. Milk fat metrics – more than meets the eye. Agri-King Advantage. November, 2018. Volume 9, Issue 6.
Schauff, D. Why did milk fat drop?….It’s complicated. Agri-King Advantage. November, 2016. Volume 7, Issue 6.
Jones, D. Feeding fat to dairy cows. Agri-King Viewpoint. June, 2006. Volume 31, Issue 2.
de Souza, J. and A. L. Lock. Long-term palmitic acid supplementation interacts with parity in lactating dairy cows: Production responses, nutrient digestibility, and energy partitioning. 2018. J. Dairy Sci. 101:3044-3056.
de Souza, J., C. L. Preseault, and A. L. Lock. Altering the ratio of dietary palmitic, stearic, and oleic acids in diets with or without whole cottonseed affects nutrient digestibility, energy partitioning, and production responses of dairy cows. 2018. J. Dairy Sci. 101:172-185.
de Souza, J., N. R. St-Pierre, and A. L. Lock. Altering the ratio of dietary C16:0 and cis-9 C18:1 interacts with production level in dairy cows: Effects on production responses and energy partitioning. 2019. J. Dairy Sci. 102:9842-9856.
de Souza and A. L. Lock. Effects of timing of palmitic acid supplementation on production responses of early-lactation dairy cows. 2019. J. Dairy Sci. 102:260-273.
Lock., A. L. Opportunities to improve fatty acid digestibility. 2019. Discover Conference.