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Effects of increasing dietary alpha-linolenic acids in nursery pigs

Objective was to determine the effectiveness of O3 Trial Feed, a source of omega-3 fatty acids and algae, on nursery pig performance and immune response.

March 10, 2022

6 Min Read
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National Pork Board

Omega-3 fatty acids (alpha linolenic acid) have been shown to improve immune function and lessen the febrile response to activate the immune system. The mode of action is thought to be through a decrease in the omega-6:3 fatty acid ratio. Specifically, research has demonstrated that lowering the ratio of omega-6:3 to a range of 3:1 or 5:1 instead of the normal 10:1 or 20:1 observed in common swine diets can increase incorporation of omega-3 fatty acids into cell membranes for utilization during immune challenges. 

O3 Trial Feed is a flaxseed omega-3 fatty acid product enriched with algae that has been used to increase omega-3 content of pork. The fatty acid profile makes it a viable option to reduce the omega-6:3 fatty acid ratio for nursery pigs and improve immune status. Incorporation of O3 Trial Feed at approximately 3% in a common nursery diet would result in a final diet containing 4:1 to 6:1 omega-6:3 fatty acid ratio depending on the composition of the basal diet.

Components of algae also have been demonstrated to provide immune benefits. We hypothesized that altering the omega-6:3 ratio and providing the algae, using O3 Trial Feed, would improve responsiveness to an immune challenge. Therefore, the objective of these studies was to determine the effectiveness of O3 Trial Feed, a source of omega-3 fatty acids and algae, on nursery pig performance and immune response

In Experiment 1, a total of 350 weanling pigs (Line 241 × 600, DNA; initially 12.7 ± 0.1 lb) were used in a 41-day trial to evaluate the effects of O3 Trial Feed, a source of omega-3 fatty acids, on nursery pig performance and response to a lipopolysaccharide immune challenge. Pigs were randomly assigned to pen (five pigs per pen), and pen randomly assigned to one of five dietary treatments with 14 replications per treatment.

The dietary treatments included increasing O3 Trial Feed (0, 1, 2, 3 and 4%). Thus, omega-6:3 ratios for the five dietary treatments by phase were: Phase 1 (18.6:1, 9.6:1, 6.4:1, 4.9:1, 4.1:1); Phase 2 (15.0:1, 9.6:1, 5.4:1, 4.3:1, 3.8:1); Phase 3 (20.7:1, 10.1:1, 6.7:1, 4.9:1, 3.8:1), respectively. Individual pigs were weighed and feed disappearance was recorded to determine average daily gain, average daily feed intake and feed-to-gain ratio.

On day 25, two pigs per pen (those closest to the average weight of the pen) were injected intramuscularly in the neck with LPS and an additional pig in each pen was injected with saline to measure immune response. Body temperature was taken from all three pigs prior to the injection (hour 0) and at two, four, six and 12 hours after injection. One blood sample was collected on the day prior to challenge and four hours after LPS injection challenge to determine immune response.

There were no differences in ADG, ADFI or F/G and no interaction between change in body temperature and inclusion of O3 Trial Feed. However, there was a main effect of time. Pigs responded as expected with an increase in body temperature at two hours post LPS challenge. Then, body temperature decreased as time post-challenge increased. There were no differences observed in IL-1β concentrations from baseline to four hours post LPS challenge.

These results indicate that dietary alpha linoleic acid level did not influence growth performance or immune response to LPS challenge. Though there was no response in growth performance or immune response in a university research setting, we conducted a companion study to test O3 Trial Feed under field conditions with pigs exposed to normal commercial stressors and diseases.

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Therefore, in Experiment 2, 1,056 weaned pigs (PIC TR4 × (Fast LW × PIC L02); initially 16.2 ± 0.1 lb) were used in a 46-day nursery trial. There were 22 pigs per pen (mixed-sex) and 12 replications per treatment. Pens were randomly assigned to one of four dietary treatments with increasing percentages of O3 Trial Feed (0, 0.75, 1.5 and 3%). Omega-6:3 ratios for the four treatments within each phase were: Phase 1 (15.1:1, 8.4:1, 5.9:1, 3.7:1); Phase 2 (16.5:1, 9.2:1, 6.4:1, 4.0:1); Phase 3 (20.8:1, 10.4:1, 7.0:1, 4.2:1); and Phase 4 (25.3:1, 12.5:1, 8:3:1, 5.0:1), respectively.

Pens of pigs were weighed and feed disappearance was recorded weekly to determine ADG, ADFI and F/G. Oral fluid samples were collected weekly to verify porcine reproductive and respiratory syndrome virus status. Pigs tested negative for PRRSV North American strain on days 7 and 14, but tested positive on days 21, 28, 35 and 42. All samples tested negative for PRRSV European strain on each collection day. 

KSU Table 2 031022.JPG

Up to day 21, there was no significant changes in growth performance (Figure 1). However, from 21 to 28, increasing O3 Trial feed increased ADG and ADFI and improved F/G. From day 28 to 35, increased O3 Trial Feed resulted in a quadratic response for ADG and F/G, with pigs fed the control or 3% O3 Trial Feed having improved performance compared to those fed 0.75 or 1.5%. During this period, increased O3 Trial Feed increased ADFI.

From day 35 to 46 and the overall combined period, feeding increasing levels of O3 Trial Feed increased ADG and ADFI, while also improving F/G. For overall growth performance, increasing O3 Trial Feed increased ADG, ADFI and F/G, resulting in pigs fed 3% O3 Trial Feed having the greatest performance for all growth measurements.

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Also, the percentage of total pig removals and mortality decreased with increased levels of O3 Trial Feed. In summary, the improvement in overall growth performance and reduction on total removals and mortalities with increased inclusion of O3 Trial Feed did not appear until after pigs tested positive for PRRSV North American strain on day 21.

In conclusion, while O3 Trial feed did not influence growth performance or response in an LPS challenge in a university research setting, there was an improvement in growth performance and a reduction in total removals and mortalities in pigs fed O3 Trial Feed in a commercial setting, when exposed to an immune challenge.

The full data is available in the 2021 K-State Swine Industry Day Reports.  

Source: Jenna J. Bromm, Mike D. Tokach, Jason C. Woodworth, Robert D. Goodband, Joel M. DeRouchey and Jordan T. Gebhardt, who are solely responsible for the information provided, and wholly owns the information. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.

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