Can Fat Supplements In Diet Improve Reproductive Performance of Dairy Cows?
Fat Supplementation and Conception Rates
According to scientific reports, it is shown that a variety of fat supplements can help improve reproduction performance of dairy cows. With that being said, what we need to learn about is the amounts of fats to feed and whether the added cost is worth it.
During the early 1900s, it has been discovered that not all fatty acids are equal in terms of nutrition. Certain fatty acids are essential in a diet while some are not.
Scientists conducted an experiments with rats. They prepared a special diet completely devoid of fats to feed the rats. After a while, the rats would develop symptoms such as stunted growth, hair and coat problems as well as reduced fertility. However, when two fatty acids, also known as linoleic and linolenic acid were added to the rats' diet, these symptoms were eliminated.
Since then, scientific knowledge regarding fatty acid nutrition has continued to advance. In the last decade or so, researches have been looking at the impact of specific fatty acids such as linoleic and linolenic acid on dairy cattle reproductive performance. While the signs of fatty acid deficiency in cows are not observable, adding selected fatty acids to the cows' diet could help improve the reproductive performance of dairy cows.
There is a hormone-like substance, known as prostaglandins which have important role in reproduction. Dairy cow's body makes them from unsaturated fatty acids. Hence, different amounts of linoleic and linolenic acids in the cows' diet can affect the reproduction.
Studies To Find Out The Effect Of Feeding Specific Fatty Acids To Dairy Cows
Recent studies from the United Kingdom are an example studies focused on the effect of feeding specific fatty acids to dairy cows. In this study, 35 non pregnant milking cows were split into groups A and B, nine weeks after calving. In group A, the cows were fed commercial fat supplement mixed with solvent-extracted flaxseed meal while group B were fed with rumen-protected whole flaxseed which provides more than twice the amount of linoleic acid compared to cows in group A. The rest of the diets were the same for both groups.
The main goal of this experiment is to find out whether cows fed with whole flaxseed would have improved reproductive performance due to the extra linoleic acid in their diet. The supplements were fed until 19th week of lactation and the measurements for milk produced 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.
The key findings of this experiments are:
Group that were fed with commercial fat-flaxseed meal supplement produced approximately one kilogram more milk per day compared to the other group, even when cows from both of the groups consumed similar amounts of feeds.
Group that were fed with rumen-protected whole flaxseed supplement had significantly higher conception rates. 14/16 cows in group B were confirmed pregnant after the first insemination compared to 7/14 cows in group A. (Note that 5 cows were not suitable to include in this study)
Amounts of Fat To Feed
A frequently asked question is "What is the optimal amount of fat to feed in order to improve reproduction?" In general, feeding fat 1.5% of dietary DM proved to be effective. With that being said, it is not known whether feeding smaller amounts would be as effective. It is entirely possible that feeding smaller amounts of fat such as 0.25 or 0.5 pounds per day would be as effective. The key fatty acids that reach the small intestine of the cow are absorbed into the bloodstream and deposited into tissues, including the reproduction tissues. Some of these can accumulate over time. Therefore, a small but steady stream of key fatty acids streaming to the tissues can allow the tissues to accumulate the fatty acids and have them ready to use at the time of reproduction. Hence, it is very possible that feeding fat less than 1.5% of dietary DM could prove beneficial.
When Is The Right Time To Initiate Fat Supplement?
It is highly recommended to start feeding fats to dairy cows well ahead of time before fats are needed for restoring the reproductive tissues to a new fertile state. This would involve the involution of the uterus, the return of the ovaries to growing and ovulating new follicles, and the uterus to receiving and maintaining a new embryo successfully. Cows that were fed with selected fat sources have responded with larger ovarian follicles. The ovarian activity usually returns within the first four weeks of calving. Hence, initiating fat feeding prepartum would allow the absorbed fatty acids to influence early ovarian activity. Therefore, it is highly recommended to feed supplemental fat for at least 21 days, preferably for 40 days, prior to the desired physiological response.
How Might Fat Supplementation Help Improve Conception Rates?
Improving Energy Status?
Lactating dairy cows experience intense negative energy state, thus having a delayed resumption of estrous cycles after parturition.
Fat supplementation increases energy intake. This will reduce the period of negative energy state and thus the estrous cycle can start sooner and conception will occur sooner.
Although there is evidence that feeding fat can help improve energy status of lactating dairy cows, but the improvement of reproductive performance occurred in several instances apart from improving energy status of the cows. Therefore, feeding fat is likely to improve reproductive performance through other means
Meeting An Essential Fatty Acid Requirement?
Both linoleic as well as linolenic acid are essential fatty acids for the cows because the body is incapable of synthesising them.
Recent studies showed that modern cows export more linoleic acid in her milk than she is absorbing from the diet, hence the cow is in negative linoleic acid balance.
Therefore, feeding fat sources rich in linoleic acid that can reach the small intestine can help reduce the negative balance of linoleic acid and improve performance.
Reproductive performance of nonruminant animals such as pigs and poultry greatly improved when the fatty acid deficiency is solved. However, with lactating cows, they do not show when there is a fatty acid deficiency.
Healthier Ovarian Follicles?
In general, larger dominant follicles is associated with higher conception rate.
When cows are supplemented with fat, the size of the dominant follicle is often larger.
Studies have shown that polyunsaturated fats were the most effective in increasing the follicle size.
The ovulation of larger follicles has improved fertility of dairy cows apart from elevated progesterone. Cows that have greater concentration of progesterone in their blood after insemination have a better chance of getting pregnant.
Better Quality Embryos Produced?
Embryos are not created equally.
A high quality embryos is when they have a symmetrical and spherical mass with individual cells that are uniform in size, colour and density.
Studies showed that cows fed with a mixture of linoleic acid and trans fatty acids tended to have fertilised structure and have more of the embryos classified as high quality.
It is however unclear if the linoleic acid or the trans fatty acid in the mixture was most responsible for this benefit.
In general, the feeding of polyunsaturated fats appears to have a more positive impact on embryo development than do monounsaturated or saturated fat supplements.
Less Embryonic Loss?
Embryonic loss is a big problem in the dairy industry.
Studies showed that omega-3 fatty acids stored in the uterus from the diet can help in the process of embryo preservation by helping to reduce the synthesis of prostaglandin F2α (if prostaglandin F2α is released by the uterus, the corpus luteum will disappear, progesterone synthesis will drop, the embryo will die for lack of support, and the cow will start a new estrous cycle).
If supplying omega-3 fatty acids helps to exert a suppressing effect on PGF2α around the time of embryo recognition, then embryo loss should be reduced.