How a yeast derivative can improve fish transfer and wound healing

Among existing best management practices, natural nutritional solutions such as specific yeast derivatives can enhance fish robustness, resilience and recovery. These are important tools to minimise the impact of handling and secure a quick recovery upon transfer, thereby optimising the production cycle.

The challenges of fish transfer 

Transporting fish from one rearing facility to another poses significant health risks. The fish are typically transported in specially designed trucks or boats that can maintain adequate conditions during transit. However, the transfer imposes many stressors, including physical handling and dewatering, abrupt changes in water quality and delivery within a novel physical and microbial environment.  

Exposure to these various stressors can cause direct wounding, including micro-lesions, as well as immune suppression, compromising the mucosal barriers, disease resilience, and end-product quality.

For example, stress is well documented to impact gut permeability as well as to induce skin mucous peel-off and loss of its physical and anti-microbial properties. Furthermore, feed intake is typically compromised for several days upon arrival, particularly when transferring from land-based to net-pen facilities. As a result, and beyond any direct mortalities, the risk of secondary diseases, lingering morbidities and poor performances is high when transferring fish that are not sufficiently robust or equipped to recover.

A nutritional solution to improve resilience and robustness 

Lallemand has developed Yang, a patented multi-strain yeast fraction, specially designed for its immune modulation power. Scientists have demonstrated its ability to elicit a broad and balanced immune modulation through synergistic effects on immune receptors. Its impact has been successfully documented in several fish species including trout, salmon, European seabass and gilthead seabream. 

It has shown clear benefits in facilitating and speeding up skin wound healing through a quicker onset of tissue rebuilding. It has proved particularly beneficial around the transfer period and during demanding conditions (e.g. handling, high temperature and infectious pressure). When transferring salmonids, it is recommended to use Yang in the transfer diet for 2 to 4 weeks prior and 2 to 4 weeks after transfer at an incorporation rate of 1-1.5 kg per tonne of feed.

Reinforcing the first line of defence

Studies with Yang in salmonids have demonstrated its capacity to reinforce the fish’s first line of defence: the skin and gill protective mucous layer. 

A feeding trial was conducted in rainbow trout (Oncorhynchus mykiss) to evaluate the effect of the yeast derivative on skin mucous production following fish transfer. When compared to the control group, a positive effect of Yang was observed within 4 weeks, with a 65 percent increase in skin mucous excretion. After 2 months, skin mucous levels were 27 percent higher in the group fed with Yang compared to the control group (Figure 1). 

By promoting a rapid recovery (under 4 weeks) and a higher level of skin mucous excretion, the yeast derivative secured the maintenance of good animal health and performance over the transfer period. The effect of Yang on skin mucous excretion and antimicrobial properties has been documented in various fish species – such as seabass, seabream and Atlantic salmon (Rawling et al., 2017, 2018; Leclercq et al., 2020;). Other studies have documented the effects of the yeast derivative on the gill, skin and gut immunity of trout juveniles (Pontefract et al., 2021) and shown a strong correlation between Yang supplementation and the gut immune response (Rawling et al., 2019, 2021).

Speeding up wound healing

Fish transfer, even if good practice is followed, inevitably induces some degree of mucosal disturbance and skin damage. Scientific studies looked into the specific effect of Yang on wound-healing (Edirisinghe et al., 2023) using an established mechanical skin wound model. In this experiment, the multi-strain yeast fractions fed continuously before dermal wounding promoted early wound healing (Figure 2). Supplementation favoured, in particular, a quicker resolution of inflammation and synthesis of granulation tissue at the wound bed (documented by histopathological diagnostics) (Figure 3). The promotion of early wound closure with Yang was associated with the modulation of a panel of genes involved in mucosal immunity and tissue rebuilding at the wound site. 

Conclusion

Fish transfer is a critical step that can seriously impair production performance and fish welfare. As part of good transfer practices, the nutritional yeast derivative Yang is an effective tool to support fish robustness and resilience with well documented benefits on the gut and skin mucosal barriers when exposed to demanding conditions. In addition, its capacity to speed up skin wound healing is expected to aid recovery after transfer and handling. 

For further information, read our these peer reviewed publications - here and here.