Conception Rate Boost - Fat Supplements in Diet Might Improve Reproductive Performance

Researchers have already determined that feeding certain fatty acids to your dairy herd could enhance reproductive performance. What we need to learn now are the amounts to feed and whether added costs would prove worthwhile.

In the first half of the 1900s, scientists discovered that not all fatty acids are nutritionally equal. Like some amino acids, certain fatty acids are essential in the diet.

Early nutritional experiments fed a specially prepared diet, completely devoid of fat, to rats. After a while, the rats would develop symptoms such as stunted growth, hair and coat problems, and reduced fertility. Two fatty acids - known as linoleic and linolenic acid - eliminated these deficiency symptoms when added back into the rats' diet.

Since then, scientific knowledge about fatty acid nutrition has continued to advance. For example, after a lot of research, North American infant formula manufacturers recently added DHA (docosahexaenoic acid) to their products. This polyunsaturated fatty acid was discovered to be important for babies' eyesight development.

In the last 10 years or so, animal scientists have been looking into the impact that specific fatty acids like linoleic 'and linolenic acid can have on dairy cattle reproductive performance. While we may not see signs of fatty acid deficiency in cows, it's possible diet supplementing selected fatty acids in their diet could improve their reproductive performance.

Hormone-like substances known as prostaglandins have important roles in reproduction. A cow's body makes them from unsaturated fatty acids. Different amounts of linoleic and linolenic acids in the diet can affect reproduction as a result.

Results from recently published United Kingdom research are an example of many studies focused on feeding specific fatty acids to dairy cows. In this study, 35 non-pregnant milking cows were split into two groups nine weeks after calving. One group received a commercial fat supplement mixed with solvent-extracted flaxseed meal. The other group was supplemented with rumen-protected whole flaxseed, giving these animals more than twice the amount of linolenic acid than the other cows. Otherwise, both groups were managed and fed the same.

The researchers wanted to find out if cows fed the whole flaxseed would have better reproductive performance because of the extra linolenic acid in their diet. The supplements were fed until the 19th week of lactation and measurements related to milk production and reproduction were recorded. Heat detection was done twice a day for hair an hour at a time after milking and equal numbers of cows from both groups were bred to one of two bulls.

Two key findings emerged from this study:

  • the group fed the commercial fat-flaxseed meal supplement produced about one kilogram more milk per day, even though both groups of cows consumed similar amounts of feed;
  • the group that ate the rumen-protected whole flaxseed supplement had significantly higher conception rates. Fourteen of 16 cows in the whole flaxseed supplemented group were confirmed pregnant after the first insemination compared to seven of 14 cows consuming the commercial fat-flaxseed meal supplement. (Five cows were unsuitable to include in study results.)

Two possibilities could explain the conception results in this experiment. The dry matter intake was similar for both groups of cows, but the higher milk production from the cows supplemented with commercial fat-flaxseed meal means they were in a greater negative energy balance. A greater negative energy balance is associated with lower reproductive performance. The other possibility was that the group fed whole flaxseed benefited from the different amounts of essential fatty acids in their diet.

Since the whole-flaxseed-fed group consumed more linolenic acid, the better conception rates could've resulted from an impact on prostaglandin synthesis in those cows, according to the researchers.

You can already buy commercially manufactured supplements for dairy cows that contain higher levels of these essential fatty acids. As well, research using supplemental fishmeal or fish oil as alternative dietary sources of fatty acids has also been shown to benefit reproductive performance.

Although benefits have been reported, precise recommendations for the amounts of particular fatty acids to feed or the ratio of one fatty acid to another are still in development. Return on investment from on-farm use of this technology also needs further investigation.

Reference: Petit, H.V, R.J. Dewhurst, J.G. Proulx, M. Khalid, W Haresign and H. Twagiramungu. 2001. Milk production, milk composition and reproductive function of dairy cows fed different fats. Can.J. Anim. Sci. 81:263-271.

This article appeared in the October 2003 Ruminations column in the Ontario Milk Producer.

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Author: Tom Wright - Dairy Cattle Nutritionist/OMAFRA
Creation Date: October 2003
Last Reviewed: 30 September 2015