Researchers with the University of California, Davis in the US and Evonik explored algae’s potential as a platform to generate beta-glucans (β-glucan) for use in piglet diets.
The group published its work in the journal of Animal Feed Science and Technology.
“The objectives of this study were to investigate the effects of algae-derived β-glucan on diarrhea, gut permeability and immune responses of weaned pigs experimentally infected with F18 E. coli,” the researchers said.
Adding high doses of the algae-derived β-glucan reduced incidents of diarrhea throughout the feeding and challenge trial, they said.
Compared to results from the control diet, the feed additive also lowered white blood cells, serum tumor necrosis factor (TNF-a), neutrophils, cortisol and haptoglobin along with influencing the expression of several immune-linked genes.
“The results of this study indicate that supplementation of around 108 mg/kg of β-glucan in animal feed could improve gut barrier function and immunity of weaned pigs and reduce post-weaning diarrhea, which will promote weaned pig health and increase profitability of pork producers as the use of antibiotics in feed is restricted,” they said.
The β-glucan used in this experiment was dried algae Euglena gracilis provided by Algal Scientific, US. The product contained around 50% β-glucan, in which 95% of them was β-1,3-glucan.
Kemin acquired Algal Scientific's beta glucan technology in 2017.
Background on piglet diarrhea and β-glucan use
Post-weaning diarrhea in pigs has been linked to about 20 to 30% of the mortality in weanling pigs, along with large economic losses for producers, said the researchers.
Consequently, multiple feed-based products have been developed to address the diarrhea challenge, they said. Many of the products focus on modulating gut microbiota or improving weaned piglet’s immune response to boost disease resistance.
β-glucans are a type of polysaccharide found in cereal grains, algae, seaweed and fungi, they said.
“The individual glucose in β-glucans are primarily linked by (1,3)-, (1,4)-, or (1,6)-β glycosidic bonds,” the researchers said. “It has been reported that the biological properties of β-glucans include anti-tumor and immunomodulatory effects in vitro.”
The immune-boosting influence of β-glucans have been demonstrated previously in pigs, mice and humans, they said. But not all types of β-glucans produce the same immune-modulatory results.
Cellulose is a β-glucan but does not generate immune-modulatory influence, they said. However, types derived from fungi and yeast have been linked to immune system regulation in animals.
“This variation is due to differences in physiochemical properties, including purity, solubility, molecular mass, degree of branching, polymer charge, chemical structure, and tertiary structure between these β-glucans,” they said. “In addition, Dectin-1 highly recognizes β-(1,3)-glucans from a variety of sources, therefore, triggers the modulation of immune system.”
Why look to algae?
Presently, most commercially available β-glucans stem from yeast, the researchers said.
However, little work has been done examining β-glucans derived from algae, especially in swine diets.
“The β-glucans extracted from algae Euglena gracilis are linked by (1,3)-glycosidic bonds and are categorized as paramylon,” they said.
Past research in vitro found that algae-derived β-glucan boosted the reaction from porcine leukocytes, they said.
“Therefore, the hypothesis of this experiment was supplementation of algae Euglena gracilis-derived β-glucan could modulate immune responses and gut integrity, therefore, enhance disease resistance and health of weaned pigs,” they added.
Feeding and disease challenge details
During the feed and disease challenge, 36 weaned piglets were given one of three diets and infected with pathogenic Escherichia coli (E. coli), the researchers said.
None of the diets included antibiotics, zinc oxide or spray-dried plasma.
The diets included a non-supplemented control and trial diets with two levels of supplemental, commercially-produced β-glucan at 54 or 108mg/kg, they said.
Piglets received the diets 5 days prior to disease exposure and were tracked for 12 days post challenge.
Piglets were scored for diarrhea twice daily and temperatures were checked daily, they said.
Researchers collected blood samples on day 0, 2, 5, 8 and 12 following the exposure to check for blood cell counts and inflammatory markers.
Piglets were weighed at weaning, the day before the start of the disease challenge and on days 5 and 12 post-infection, they said.
Feed intake was recorded and average daily feed intake, average daily gain and the feed conversion ratio were established.
A selection of piglets was harvested to allow for the collection of jejunal tissues and analysis of gut permeability on day 5 and 12 following infection, the researchers said.
Mucosa from the jejune and ileal also was collected.
Results
Throughout the experiment, body weight, average daily gain, average daily feed intake and feed efficacy remained similar for pigs regardless of diet, the researchers said.
However, piglets on the low-dose supplemented diet had lower temperatures on days 5 and 7 post-infection than those on other diets, they said.
Adding the high dose of B-glucan improved fecal consistency on days 3 and 5 post-infection (PI) and reduced frequency of diarrhea during the entire trial compared to those on the other diets.
Pigs on the low-dose diet had a lower number of white blood cells compared to the control, they said.
Piglets on both supplemented diets had lower serum haptoglobin on days 2 and 5 post-infection and reduced cortisol on days 5, 8 and 12 post-infection.
Additionally, pigs on the high-dose diet had reduced jejunal transcellular permeability on day 12 post-infection, the researchers said.
The supplement also “up-regulated” expression of Dectin in the jejunal mucosa and ileal mucosa compared to the control diet, while reducing IL6.
“Results of this experiment indicate that in feed supplementation of approximately 108 mg/kg of algae-derived β-glucan alleviated diarrhea of F18 E. coli infected pigs by enhancing gut integrity.
“Feeding algae-derived β-glucan also boosted host immune response against E. coli infection.
“The β-glucan product stimulated T cell activation and reduced inflammation and, therefore, may accelerate the recovery of pigs from E. coli infection,” they added.
Source: Animal Feed Science and Technology
Title: Algae-derived β-glucan enhanced gut health and immune responses of weaned pigs experimentally infected with a pathogenic E. coli
Authors: K. Kim, A. Ehrlich, V. Perng, J. Chase, H. Raybould, X. Li, E. Atwill, R. Whelan, A. Sokale, Y. Liu
DOI: doi.org/10.1016/j.anifeedsci.2018.12.004
