Feeding fat to dairy cows: A complex subject

Feeding fat and fat products to dairy cows is common on most, if not all, dairies. Understanding how to properly feed fats and fat products is another story and seems to change daily.

This is especially true as we work to understand the roles various fat components (fatty acids) play in the animal in terms of production (volume and components), health and reproduction.

And while it may not be necessary, let’s remember that fat feeding in the dairy animal is broken into three areas:

1. The level of fat inherently found in feed ingredients – forages, grains, low-fat proteins as well as higher-fat products such as whole cottonseed, distillers grains, corn germ meal and so on. Most forages and grains make at least some contribution to the total dietary fat level.

While recommendations vary by understanding and experience, somewhere around 3 percent fat in the basic part of the ration has been shown effective.

2. Secondary sources of added fat 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 pound per head.

3. More recent efforts have seen the emergence of feeding rumen-protected fats, particularly palm fat. 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 percent total fat in a given ration. So now that the basics are out of the way, let’s proceed.

This article will focus on three areas currently of concern to the industry related to feeding fats and fatty acids to the dairy cow. Each area of discussion is important to the development of the overall nutrition program on the dairy.

Feeding palm fats

Feeding rumen-protected or bypass fats is not new. It is a common practice for dairymen working to increase energy intake in high-producing cows to support production and components. 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 point when feeding palm fat.

Keep in mind milkfat is made up of different types of fatty acids. Approximately 50 percent of milk fat composition comes from short-chain fatty acids – up to 16-carbon fatty acids chains. These are manufactured in the udder (de novo synthesis) that is supplied largely by volatile fatty acids produced by rumen fermentation of feeds and forages.

The other 50 percent 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 milk fat 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 C16:0 content.

Processed palm fat has a high melting point, around 135ºF. 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 to and then drawn off by the udder and synthesized into milk fat.

Regardless 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 upon raising milkfat yield.

Feeding higher-fat soybean sources

Recent research at Penn State University reported that changing to a higher-fat soybean meal could improve dry matter intake and milk production while supporting butterfat. One trial substituted a heat-processed, high-fat (10 percent) soybean meal for solvent-extracted soybean meal containing 1.8 percent fat in lactating dairy cow diets.

The high-fat soybean meal diet showed a dry matter intake increase of 2.65 pounds per cow per day with improved milk production of 7.5 pounds per cow per day compared to cows fed conventional solvent-extracted soybean meal. Total fat content in diet dry matter was 4.3 percent. Other parameters, milkfat, milk protein and feed efficiency did not change.

While increased fat in the diet appeared to drive part of the response, it did not appear responsible for everything. Workers also believed palatability was a key as well.

The combination of increased palatability due to higher fat content increased energy density in the diet due to additional fat and increased rumen-undegraded protein supply from the heat treatment during processing all appeared to play a role in the end result.

In many cases, if basic ration fat levels are around 3 percent, lactating cows can benefit from up to an additional 2 to 3 percent total fat in the ration. While the solvent-extracted soybean meal product used in the study was a 10 percent fat extruded soybean meal, there are other heat-treated soybean meal products with up to 6.6 percent fat that could still deliver an increase in dry matter intake and milk production.

In the Penn State study, the key was the palatability of the product and the increased dry matter intake.

Fat supplementation and conception rates

Switching gears somewhat, according to various scientific reports, in addition to contributing to increased production and milkfat, a variety of fat supplements have been shown to help improve reproduction performance of dairy cows.

Early research showed not all fatty acids are equal from a nutritional perspective. Some are more essential than others. Initial work with rats showed treatment diets where the fat had been removed resulted in animals showing symptoms such as stunted growth, hair and coat problems as well as reduced fertility.

However, when two fatty acids, linoleic and linolenic acid, were added to the rats’ diet, these symptoms disappeared.

More recently, researchers have been looking at the impact of linoleic and linolenic acids on dairy cattle reproduction. While 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.

Recent work in the United Kingdom focused on the effect of feeding specific fatty acids to dairy cows. In one study, 35 open lactating cows were split into two groups nine weeks post-calving. The first group was fed commercial fat supplement mixed with solvent-extracted flaxseed meal.

The second group was fed rumen-protected whole flaxseed, which contained more than two times the level of linoleic acid compared to the diet fed to group 1. Remaining diet nutrients were identical.

Findings of this experiment included:

The group fed the commercial fat-flaxseed meal supplement produced approximately 2 pounds more milk per day compared to the second group, even when cows from both groups consumed similar levels of dry matter.
The second group fed the rumen-protected whole flaxseed supplement had significantly higher conception rates: 87.5 percent of cows in group 2 were confirmed pregnant after first inseminations compared to 50 percent of the cows in group 1.

So a question becomes: How does fat feeding improve conception rates? Some possible answers include:

Improving energy status
Meeting one or more essential fatty acid requirements
Improved health of ovarian follicles
Improved embryo quality
Reduced embryonic loss

All of these responses have been attributed to feeding supplemental fat to dairy cows.

Conclusions

As noted at the beginning of this discussion, fat feeding to dairy cows is a complex subject, yet research has shown a wide variety of results. Future efforts will likely include feeding of specific fatty acids and a better definition of the responses for production, health and reproduction.

This article was originally published on www.progressivedairy.com and is reproduced with permission from the author.