Seaweed supports improved intestinal health and resilience

A considerable body of literature exists to demonstrate the range of bioactive compounds in seaweed, and their applications in animal feed. As strong evidence has accumulated in recent years for the prebiotic effects of seaweed polysaccharides, animal producers are realising the potential benefits of enhancing populations of beneficial gut bacteria on intestinal health and animal performance.

Macroalgae (seaweed) are an important source of functional ingredients for animal nutrition, due to their diverse nutritional composition, and their high content of bioactive compounds such as polysaccharides, pigments, peptides and polyphenols. Various published reviews have summarised the anti-inflammatory, antioxidant, prebiotic and antimicrobial properties of macroalgae (Xie et al., 2023, Gonzalez Meza et al., 2023, Morais et al., 2020), demonstrating the wide range of applications in animal feed.

A SUSTAINABLE SOURCE OF BIOACTIVE INGREDIENTS
Utilising blends of whole seaweeds in animal diets enables producers to realise the benefits of the variety of bioactive compounds in macroalgae, whilst also reducing the environmental footprint of animal feed. Seaweed requires no fresh water, land use or fertiliser for growth, and so compares very favourably to terrestrial feed ingredients (Duarte et al., 2017). In cases where wild seaweed is harvested from algal blooms, the environmental impact is even more favourable, due to the recycling of nutrients derived from land-based agricultural run-off.

MULTIPLE MODES OF ACTION TO SUPPORT GUT HEALTH
The use of seaweed polysaccharides as prebiotics in animal nutrition has been comprehensively described in the literature (Makkar et al., 2015, O’Sullivan et al., 2010). Furthermore, studies have demonstrated the prebiotic effects of whole seaweed blends, positively influencing the profile of the gut microbiome in swine (Hutchinson 2023), and the cecal microbiome of broilers (Sands, 2022) to enhance gut health and animal performance. The improvements in intestinal health achieved as a result of seaweed supplementation have also been shown to be cost effective. Feed costs per kg of liveweight gain were reduced in nursery pigs supplemented with a blend of whole seaweeds, compared to those supplemented with a number of other gut health additives, including phytogenic ingredients and yeast cell wall extracts (Hutchinson, 2023).

Recent research has identified further benefits of macroalgae supplementation on gut health, beyond the strong prebiotic effects detailed above. Initial in vitro studies conducted by Ocean Harvest Technology confirmed the potential for OceanFeedTM seaweed blend to bind three important pathogens (Clostridium perfringens, Escherichia coli and Salmonella Enterica serovar Typhimurium) and form agglomerates, with binding efficiencies of 60%, 42% and 76%, respectively. The agglomeration capacity demonstrated in this work shows how supplementation of animal diets with blends of macroalgae can contribute to the inhibition of pathogenic colonisation in the digestive tract, supporting improved gut health and animal performance.

REDUCING THE NEGATIVE IMPACTS OF NECROTIC ENTERITIS IN BROILERS
In order to further develop this hypothesis, Ocean Harvest Technology engaged Southern Poultry Research Group to conduct a Necrotic Enteritis Challenge trial at their facility in Georgia, USA. In this study, a total of 400 Ross 308 broilers were fed one of 4 dietary treatments for the duration of the 28-day trial;
• Negative Control (NC, standard commercial diet)
• Challenge Control (CC, NC + Necrotic Enteritis challenge)
• CC + OFP 2.5 kg/t (Challenge Control + 2.5 kg/t of OceanFeed Poultry seaweed blend)
• CC + OFP 5.0 kg/t (Challenge Control + 5.0 kg/t of OceanFeed Poultry seaweed blend)
The challenge model consisted of ~750 oocysts E. maxima on day 14 of the study, and Clostridium strain on Days 19 and 20 of the study, using 1.0 mL of a 1.0 x 108 CFU/mL combination by gavage, as previously published by Hofacre, et al. (1998). The trial was established as a completely randomised block design, with 10 birds per pen, and 10 pens per treatment. The diets were formulated according to NRC guidelines with feedstuffs commonly used in the U.S. Rations were fed ad libitum from date of chick arrival to the conclusion of the trial. Birds and feed were weighed on days 0, 14, 22, and 28 of the study to evaluate performance metrics. Date and removal weight was recorded on all birds culled or found dead, and a gross necropsy was performed on all dead or culled birds to determine the bird sex and probable cause of death.

A very strong challenge resulted in high mortality in the Challenge Control Group, of 49%. Supplementation with 5 kg/t OFP significantly reduced mortality to 33%, whereas mortality in birds supplemented with 2.5 kg/t OFP was intermediate to these groups at 44%, and 0% mortality was observed in the Negative Control group. Feed intake, liveweight gain and feed conversion ratio for the entire 28-day trial period are shown in Figure 1. Liveweight gain in birds supplemented with 2.5 kg/t OFP was significantly greater than those in the challenged control group. Feed intake was significantly greater in both OFP groups compared with the challenged control group. Feed conversion ratio in birds supplemented with 5 kg/t OFP was significantly lower than birds in the challenge control group, and was not significantly different compared with birds in the unchallenged control group.

The performance of the birds after the strong challenge (from day 22 to day 28 of the study) had subsided is shown in Figure 2. Birds supplemented with OFP demonstrated an enhanced recovery and compensatory growth following the challenge, with both the 2.5 kg/t and 5 kg/t supplemented birds having significantly higher weight gain compared with the negative control and challenge control groups. These results show that OceanFeed Poultry had a significant impact on minimising the negative consequences of Necrotic Enteritis, and demonstrate new mechanisms by which seaweed blends can support enhanced intestinal health in broilers.

SUMMARY
A considerable body of literature exists to demonstrate the range of bioactive compounds in seaweed, and their applications in animal feed. As strong evidence has accumulated in recent years for the prebiotic effects of seaweed polysaccharides, animal producers are realising the potential benefits of enhancing populations of beneficial gut bacteria on intestinal health and animal performance. Recent research conducted by Ocean Harvest Technology has demonstrated additional benefits beyond these prebiotic effects, mediated through agglomeration of pathogens in the intestinal tract, and possible stimulatory effects on the immune system.

About Dr. Ian Hutchinson
Dr. Ian Hutchinson is Technical Director at Ocean Harvest Technology, having previously worked for 9 years in the feed additives and premix industry. In his role as Technical Director, Ian is responsible for developing and driving the Ocean Harvest Technology’s research and development agenda as well as customer technical support and product trials.