European pork producers have a swine ration component that gives them a nutritional advantage — the availability of fish oil.
There may not be a huge amount of data, but it looks like pigs can benefit from omega-3 fatty acids, much like people do. It's not just any fatty acid, however, that gets credit for a positive response.
“The long-chain carbon fatty acids found in marine oils are the focus,” says John Rooke, a swine nutritionist with the Scottish Agricultural College. Those of particular interest are linolenic, eicosapentaenoic (EPA) and docosahexaenoic (DHA).
Tuna is the best source of the more valuable EPA and DHA fatty acids, but it is not cost effective. So salmon, menhaden and mackerel oil provide those desirable long-chain acids.
According to Rooke, there are about eight products on the market that contain marine oil. Only one, Fertilium (see sidebar), is available in the U.S.
The Scottish scientist spoke on the use of long-chain fatty acids in sow diets during the Minnesota Nutrition Conference last fall in St. Paul, MN. His studies have centered on gestating sows and the effects of specific fatty acids on preweaning death loss.
Rooke has found that feeding salmon oil from Day 60 of gestation through farrowing increased the weight of brain tissue. Whether or not that accounts for the noticeable improvement in viability, he's not sure.
But preweaning mortality dropped significantly from 11.7% to 10.2% in a large commercial study, mostly due to fewer pigs being crushed. The progeny of sows fed fish oil were lighter at birth, but there was no difference in weaning weights.
Most neonatal growth occurs after Day 60, and this is when long-chain fatty acids transfer to the organs, including the brain, is most likely to occur, says Rooke.
Like most mammals, the lipids of brain, retina and spermatozoa in the pig contain substantially higher proportions of 22:6 n-3 (DHA) than other tissues. Most deposition of DHA occurs during late pregnancy, and experimental models have shown that a deficiency at that time causes changes in brain function in the offspring. Thus, improving the omega-3 status of the brain in a fetal pig may improve neonatal vitality, he points out. Increasing the DHA content of spermatozoa has also been associated with improved sperm function and ability to fertilize.
There are well-documented effects of fatty acids on gene expression as well, Rooke notes. This is a rapidly developing area of research and the number of factors regulated by fatty acids is increasing.
Cereal grains contain only small amounts of omega-3 acids, and so pig diets using cereal grains and common protein supplements normally have omega-6 to omega-3 ratios greater than 10 to 1, which are considered imbalanced in human nutrition. Only flaxseed provides a supply of omega-3 fatty acids, but not the longer chain acids found in fish oils.
“Flaxseed oil is a very good source of linoleic acid, and it will reduce the ratio of omega-6 to omega-3 acids in the diet to nearer the desirable range of 4 to 8:1. But we need to be careful about whole flaxseed and attributing responses only to the 18:3 n-3 (omega-3), as there may be undefined trace components in the flaxseed that contribute to responses,” says Rooke.
“The 18:3 n-3 fatty acids in flaxseed will convert to EPA, and to a lesser extent to DHA, but the pig does not do this efficiently. The question is: Is the extent of the conversion sufficient to meet requirements? Our data says no,” he adds.
It is also important that the correct amounts are fed. Rooke explored an optimum by feeding sows increasing levels of fish oil from Day 60 and measuring response by changes in brain weight and fatty acid composition. The optimum inclusion, he says, was 10 g. oil/kg. (2.2 lb.) of diet, which corresponded to 6 g./sow/day of EPA and DHA together (total intake 5.5 lb./day), or 0.6% DE intake. On cost grounds, he recommends feeding 1%, or about $5/sow/year.
Rooke points out that given the highly polyunsaturated nature of marine oils and their susceptibility to oxidation, it is notable that marine oils contain varying concentrations of the antioxidant vitamin E.
In the United Kingdom, vitamin E is added to stabilize the oil. “This may have been overkill, as vitamin E levels this side of the pond (U.S.) are usually around two times the requirement. In products such as Fertilium, the encapsulation process protects the fatty acids from oxidation and makes them easier to handle,” he notes.
Many mills simply spray the oils onto product to act as a binder. “In the long run, the practicality and ease of handling with solid products and protection from oxidation may well turn out to be the method of choice for delivering fish oils into feed,” Rooke says. “It also takes the risk away from the mill or unit actually producing the diet.”
In conclusion, the Scottish nutritionist says there is evidence that piglet survival and growth may benefit from including a source of long-chain fatty acids in sow diets. The amount and type of fatty acid to be included, both during ovulation and early pregnancy and during the time of rapid fetal tissue deposition, require further study.
Chemically, omega-3 fatty acids are long chains of carbon atoms (18 to 22), with three to six double bonds (unsaturation sites) in the chain. The “omega” carbon refers to the final carbon at the end of the fatty acid's carbon chain. This carbon is usually designated as the “n” carbon.
Thus, omega-3 fatty acids (n-3) contain their first double bond at the third carbon, while omega-6 fatty acids (n-6) have their first double bond at the sixth carbon atom in the chain. The terms long-chain and short-chain omega-3 fatty acids generally refer to EPA/DHA and alpha-linolenic acid, respectively. Generally, the oilier the fish, the more omega-3 fatty acids are present.
United Feeds Inc. developed and markets Fertilium, a dried, processed blend of omega-3 fatty acids, protein, vitamins and minerals. The source of its marine-derived oil is proprietary, and the encapsulation process to stabilize the fatty acids is patent pending, but the product does contain the long-chain fatty acids eicosapentaenoic (EPA) and docosahexaenoic (DHA).
Company field trials have shown an increase of 0.6 pigs/litter from sows fed Fertilium for 28 days, from farrowing through breeding. It is normally added to the lactation diet and top-dressed during breeding. The product should be used within four weeks of delivery. Fertilium replaces 15 lb. of corn and 15 lb. of soybean meal/ton. Sows should receive 3 oz./day. The cost is about $5/sow/lactation.
There can be problems with implementation, admits Steve Webel, director of reproduction research and development. “We know (feeding for) four weeks is required prior to breeding to get maximum effect. Some farms may not be able to take advantage of the product's benefits because of early weaning. If the lactation and rebreeding period is less than 28 days, sows would need to be fed prior to entry into the farrowing room. Our ongoing research is directed at developing a second-generation product in a program that is more convenient to implement.”
Fertilium helps to balance the omega-6 to omega-3 fatty acids in a proper ratio. “Human nutritionists suggest we consume diets that have a 5:1 ratio,” explains Webel. “A typical sow diet has a ratio greater than 20 to 1, since corn is high in omega-6. Fertilium reduces the ratio to less than 10:1.”