Algal immunomodulator may improve broiler health

Algal immunomodulator may improve broiler health

A new beta-glucan feed additive derived from algae shows promise as a growth promoter through natural enhancement of immune activity.

*Dr. Robert B. Levine is with Algal Scientific Corp. in Northville, Mich.

DIETARY immunomodulators may offer a cost-effective method for increasing the productivity and economic competitiveness of broiler chicken operations by improving the birds' disease resistance and stress tolerance, increasing the effectiveness of vaccines and reducing the need for more drastic and expensive disease control measures.

In particular, natural immunomodulators may reduce the need to use subtherapeutic doses of antibiotics, which are increasingly unpopular with consumers and are becoming more highly regulated. Healthier broilers are also more productive and efficient, meaning the appropriate use of high-quality immunomodulators can lead to improved growth rates and feed conversion ratios.

 

Beta-1,3-glucan

A significant amount of research on immunomodulators has focused on beta-glucans, a class of polysaccharides composed of chains of glucose molecules connected though glycosidic linkages. The most immunologically active forms of beta-glucans contain a beta-1,3-glucan backbone, which is recognized by the immune system of higher organisms since it is typically associated with the surface of pathogenic microorganisms.

By introducing beta-1,3-glucan into the diet of broiler chickens without a pathogenic challenge, one can prime the animal's immune system so that its response to an actual disease challenge, stress or vaccination protocol is more robust. As an additional benefit, beta-glucans can bind a variety of mycotoxins in feed and limit their bioavailability in the digestive tract.

To date, the vast majority of research on beta-glucans for use in animal diets has been conducted with beta-glucans derived from yeast. Yeast cells contain about 5-15% beta-glucans on a dry weight basis in the form of a beta-1,3-glucan backbone containing numerous branches connected via beta-1,6 linkages.

This beta-glucan is found predominantly in the cell wall, where it is bound to other cellular constituents such as mannoproteins and chitin. To increase its bioavailability, yeast beta-glucans are typically extracted from the cell wall with strong acids, bases and solvents, yielding finished products with 30-65% beta-glucan content by dry weight.

While several published studies have suggested that purified yeast beta-glucans may improve performance in broilers, these products tend to be used sparingly, most likely due to their high costs.

The purpose of this article is to evaluate recent evidence about a new, lower-cost beta-glucan feed additive derived from microalgae to determine its suitability for use in poultry feeds.

 

Microalgae beta-glucans

Algal Scientific Corp. has developed a unique zinc polysaccharide complex (trade name Algamune ZPC [AZPC]; Association of American Feed Control Officials definition 57.29) that contains linear beta-1,3-glucan derived from a natural, non-genetically modified microalgae.

Using a proprietary process, the microalgae are grown in a controlled, sterile fermentation system and harvested when they contain about 45% beta-1,3-glucan content by weight. The biomass is then complexed with zinc (from zinc sulfate) under controlled conditions and dried to produce the finished feed ingredient.

(For international markets, a version without zinc is also available under the name Algamune AM.)

AZPC contains unbranched beta-1,3-glucan in the form of granules that are not associated with other cellular components (e.g., cell walls) and is comprised of more than 90% beta-1,3-glucan linkages. As a result, the beta-1,3-glucan is readily bioavailable and digestible.

By combining beta-1,3-glucan with zinc, another compound known to be important for animal health, AZPC can be used to meet an animal's nutritional zinc requirements while also providing a source of beta-1,3-glucan.

 

Mouse studies

Over the last two years, studies in mice as well as four studies at two well-known poultry research facilities have demonstrated the efficacy of AZPC in broilers.

First, mouse studies were carried out to determine how the beta-glucan in AZPC affects the immune system. This work demonstrated that the beta-glucan stimulated the mouse's immune system (e.g., by significantly increasing phagocytosis, antibody formation and natural killer cell activity) and performed similar to or better than two yeast beta-glucan products on the market.

The beta-glucan in AZPC was also found to protect mice from a bacterial challenge. In a challenge test with a lethal dose of pathogenic Escherchia coli, 50% of mice fed AZPC without zinc survived for 10 days, compared to 0% survival for the control, 40% survival for mice fed a yeast beta-glucan product and 70% survival for mice fed an antibiotic (ampicillin). When challenged mice received a purified form of the beta-glucan from AZPC, 70% survived for 10 days.

These data suggest that through natural enhancement of the animal's immune system, it is possible to greatly improve disease resistance and reduce mortality.

 

Broiler trials

In two studies at Texas A&M University from February to April 2013, inclusion of AZPC in the diet of male Cobb broilers at 250 g per metric ton significantly improved early performance in healthy broilers, with a 1.6% bodyweight increase and -3.4% mortality-corrected feed conversion ratio (FCR) compared to control birds at day 14. However, it had an even greater effect in birds challenged with 100x dose of Coccivac-B, showing a 4.1% bodyweight increase and -5.2% mortality-corrected FCR compared to challenged control birds at day 20.

In a third study at Texas A&M, day-old birds received a Newcastle/bronchitis vaccine (with a booster dose on day 18) and were fed either 0 g (control) or 250 g/mt AZPC for the first 14 days and then a control grower diet until day 25. At the conclusion of the study, the birds receiving AZPC had significantly higher Newcastle titers — 150% higher than the control group.

These data suggest that AZPC can improve bodyweight gain and FCR in young male broilers, especially those challenged by disease, and serves as an effective vaccine adjuvant in broilers. By making vaccines more effective, AZPC may enable the use of lower doses of or reduce the need for booster shots.

These initial studies were followed by a dose response performance trial at a commercial research facility (OK Farms in Arkansas) in July and August 2013. Newly hatched male Ross x Ross 708 chicks were placed into 96 pens, with 22 birds per pen at 0.75 sq. ft. per bird. They were fed three diets containing various amounts of AZPC (Table 1). There were eight treatment groups in total, each studied in 12 replicate pens. Bodyweight and FCR were calculated at feed changes on days 14, 29 and 49 (Table 2).

Birds on treatment 2, which received 125 g/mt of AZPC (providing 43.8 parts per million of beta-glucans plus 12.5 ppm of zinc in the feed) for the full 49 days, demonstrated the largest improvement in performance relative to the control group (treatment 1): The growth rate was 3.4% faster and the mortality-adjusted FCR was 1.9% lower. When this FCR was standardized to a 7.5 lb. bird, this treatment group showed a 4.1% improvement versus control birds.

Chicks on treatments 6 and 7, which were step-down dose regimens, also showed substantial improvements relative to the control birds. In treatment 6, the use of 500 g/mt of AZPC in the starter diet and no subsequent exposure resulted in an overall 3.4% improvement in growth rate, with a 0.5% mortality-adjusted improvement in FCR. For treatment 7, with 250 g/mt AZPC in the starter, 125 g/mt in the grower and none in the finisher feed, overall growth rates were increased 2.0%, and mortality-adjusted FCR was improved 0.2% relative to the control.

Mortality/cull rates among treatments ranged from 4.2% to 10.2%, with the highest mortality/cull losses occurring in the last four days of the trial (days 45-49). The mortality/cull rate was not significantly different between the control group and treatment 2.

The study at OK Farms demonstrated smaller performance enhancements relative to control birds with doses of AZPC higher than 125 g/mt, suggesting that this dose — or perhaps even a lower dose — may be the optimal inclusion rate.

With the currently available data, inclusion of AZPC in the diet at 125 g/mt is likely to provide significant benefits to producers through reduced feed costs, higher barn throughput and reduced disease impact. At this rate and given current feed costs, producers using AZPC may realize a return on investment of three to five times or more.

 

Availability

Future studies will be conducted to elucidate whether even lower doses are optimal. AZPC will be available in commercial quantities, shipped in 50 lb. bags on pallets, beginning in March.

 

1. AZPC doses (g/mt) during the production cycle for each treatment group

Treatment

 

 

 

group

Starter

Grower

Finisher

1

0

0

0

2

125

125

125

3

250

250

250

4

500

500

500

5

500

125

0

6

500

0

0

7

250

125

0

8

250

0

0

 

2. Broiler performance results by treatments to 49 days of age

 

-Treatment group-

 

1 (control)

2

3

4

5

6

7

8

Birds placed

264

264

264

264

264

264

264

264

Birds processed

247

246

250

252

247

237

238

253

Mortality/culls, %

6.44

6.82

5.30

4.55

6.44

10.23

9.85

4.17

Average weight, lb.

7.660

7.920

7.642

7.767

7.707

7.919

7.812

7.699

FCR1

1.877

1.844

1.851

1.853

1.859

1.919

1.870

1.854

FCR (mortality adjusted)2

1.816

1.781

1.821

1.816

1.826

1.807

1.811

1.829

FCR (adjusted to 7.5 lb. bodyweight)3

1.850

1.774

1.828

1.809

1.825

1.849

1.818

1.820

Growth rate, lb./day

0.156

0.162

0.156

0.159

0.157

0.162

0.160

0.157

EPEF4

365.7

383.9

368.3

378.2

365.8

364.6

360.3

373.8

1FCR = lb. of feed/lb. of liveweight of surviving birds delivered to plant.

2FCR mortality-adjusted = lb. of feed/lb. surviving birds plus lb. of dead/culls.

3FCR adjusted to a common bodyweight = adjustment to 7.5 lb. bodyweight using 0.06 lb. = 0.01 point of feed conversion change.

4European Poultry Efficiency Factor = (liveweight [kg] x livability [%] x 100)/(age in days x FCR).

 

Volume:86 Issue:04

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