Every dairy includes some level of fat in the cow’s diet, whether specifically formulated in or not. The understanding of how to properly feed fats and fat products has grown immensely over the years, but as with all dairy cow nutrition, we still have a great deal to learn. While we are well acquainted with the various sources both natural and commercial, the roles that various fat sources, fat components (fatty acids) and fat combinations play in the animal, in terms of production, health and reproduction, still need a great deal of work.
Let’s take a second and review. Fat feeding in the dairy animal is broken into three sources:
- The level of fat inherently found in feed ingredients – This is the fat found in forages, grains, low-fat proteins and high-fat products, such as whole cottonseed (~18.6%), distillers grains (~8.1%), corn germ meal (~12%), ground flaxseed (~28.7) and so on. Most forages and grains make at least some contribution to the total dietary fat level. For instance, corn silage may contain around 3.2% while alfalfa hay might contain around 2.6%. While recommendations vary by understanding and experience, somewhere around 3% to 4% fat in the basic part of the ration has been shown to be effective.
- Secondary sources of added fat – These have been shown by research to further complement this ration requirement. This may include low levels of certain vegetable oils and tallows. These supplemental fats must be included carefully and not overfed. These fats should not exceed 0.5 to 0.75 pounds per head. This may include both animal or vegetable sources of fats, liquid and dry. To help reduce the effect on fiber digestion by the use of liquid fats, sources with a higher melting point (animal-based, tallow) are generally more effective. However, because of its fatty acid profile, palm fat has seen a significant increase in use over recent years.
- Rumen-protected fats – More recent efforts have seen the emergence of feeding rumen-protected fats, many of which are calcium soaps of palm fatty acids. Recommendations for many of the commercial sources can range up to a pound or more per head per day.
Overall, when these sources are combined, it is wise to not exceed 6% total fat in a given ration. As noted, there are numerous sources of fat that can be used in the dairy diet for a variety of outcomes. Let’s consider some recent work that helps illustrate the use of different sources.
Feeding higher-fat soybean sources
A study at Penn State University reported that changing to a higher-fat soybean meal could improve DMI and milk production while supporting butterfat. One trial substituted a heat-processed, high-fat (10%) soybean meal (HFSBM) for solvent-extracted soybean meal (SBM) containing 1.8% fat in lactating dairy cow diets. The HFSBM diet showed a DMI increase of 2.65 pounds per cow per day with improved milk production of 7.5 pounds per cow per day when compared to cows fed conventional SBM. The total fat content in diet DM was 4.3%. Components and milk per feed were unaffected.
In many cases, if basic ration fat levels are around 3%, lactating cows can benefit from up to an additional 2% to 3% total fat in the ration, depending on the source. In this situation, while the SBM product used in the study was a 10% fat-extruded soybean meal, there are other heat-treated soybean meal products with up to 6.6% fat, which could still deliver an increase in DMI and milk production.
Feeding of palm fats
With the continued growth and drive to produce increased milkfat, palm fat and commercial bypass palm fat sources have grown increasingly popular as ration components. Many producers have seen an increase in butterfat of 0.2 to 0.4 percentage points when feeding palm fat.
Keep in mind that milkfat is made up of different types of fatty acids. Approximately 50% of milkfat composition comes from short-chain fatty acids – up to 16-carbon fatty acids chains. These are manufactured in the udder (de novo synthesis), which is supplied largely by volatile fatty acids produced by rumen fermentation of feeds and forages. The other 50% milkfat portion comes from those fatty acids which have been absorbed directly from the bloodstream. Compared to synthesized fats, blood-borne sources of fatty acids in milkfat are primarily made up of longer 16- to 18-carbon fatty acids. As such, rumen bypass palm fat may be considered a natural choice to raise milkfat production because of its naturally high palmitic acid (C16:0) content.
Processed palm fat has a high melting point, around 135°F. Subsequently, it easily bypasses the rumen and is digested in the small intestine of the dairy cow. Here, C16:0 fatty acid chains are absorbed into the bloodstream, transported, drawn off by the udder and synthesized into milkfat.
Regardless of what palm fat supplement is added to the diet, it is critical to avoid overfeeding all dietary fat in one capacity or another. Including palm fat should complement the rest of the dairy diet, rather than just focusing on raising milkfat yield.
Fat supplementation and effects on fertility
In addition to contributing to increased production and milkfat, a variety of fat supplements have been shown to help improve the reproduction performance of dairy cows.
Recent studies have looked at the impact of linoleic and linolenic acids on dairy cattle reproduction. While outward signs of fatty acid deficiencies in cows may not be observable, adding certain fatty acids to the cows' diet could help improve reproductive performance. One known effect is the synthesis of prostaglandins from unsaturated fatty acids, such as linoleic and linolenic acids, in the cows' diet.
Research in Great Britain focused on the effect of feeding specific fatty acids to dairy cows. Treated cows were fed rumen-protected whole flaxseed, which contained more than two times the level of linoleic acid compared to the diet fed to control cattle. The remaining diet nutrients were identical.
The findings included:
- The group fed the commercial fat-flaxseed meal supplement produced approximately 2 pounds more milk per day compared to controls, even when cows from both groups consumed similar levels of dry matter.
- The treatment group fed the rumen-protected whole flaxseed supplement had significantly higher conception rates: 87.5% of cows were confirmed pregnant after first inseminations, compared to 50% of cows in the control group.
Conclusions
Fat feeding in dairy rations has been well established as a valuable part of a well-designed nutrition program. The continued evaluation and development of new fat sources show increasing promise as we work to improve dairy cow performance and well-being.
