Feed additive 'reduced number of gravid female lice by 60%'

A feed producer has introduced a new product that it says reduced the number of ovigerous female Caligus rogercresseyi lice per salmon by more than 60% in trials.

Salmofood, a brand of Vitapro Chile, has launched Vitalice, a natural nutritional solution that is incorporated into feed as a complementary tool in integrated management lice programmes. The launch took place at the Aquaculture Solutions Meeting organised by Fish Farming Expert’s Chilean sister site, Salmonexpert.cl, last Tuesday, October 20, in Punta Arenas.

Rodrigo Sánchez, research and development manager of Vitapro Chile, presented the results of two studies developed and scientifically validated at the company's Aquaculture Experimental Centre (CEA), where natural nutritional formulations were evaluated as non-pharmacological strategies for the control of Caligus in Atlantic salmon.

Double action

He said lice control has traditionally relied on the use of oral antiparasitics or bath treatments that require periods of fasting, stress the fish through handling, and generate resistance in the parasite – all of which have a significant economic impact on the production process.

In response to this, dietary supplementation with natural bioactive compounds is emerging as a complementary strategy of growing scientific interest, aimed at strengthening the fish's immunity and reducing its parasitic load.

“We developed a formulation with naturally occurring compounds that work synergistically. On the one hand, they modulate the fish's immune response, and on the other, they interfere with the parasite's development, affecting its reaching adulthood and significantly reducing the number of egg-bearing females. This results in a more resilient fish with a more robust mucosal barrier against infestation,” explained Sánchez.

Infestation challenge

The trials were conducted using an infestation challenge methodology designed, validated, and standardised by the CEA. Atlantic salmon were exposed to a controlled infestation with C. rogercresseyi copepodites and monitored until the parasite reached the adult stage.

The different diets developed by the company were compared with a control group without supplementation and with a conventional medicinal treatment at therapeutic doses.

“We conducted two trials where we supplemented the fish for an average of 45 days. Vitalice consistently showed remarkable performance, reducing the average number of egg-bearing females per fish by more than 60%. This is a key indicator because it decreases the pressure of reinfestation at the fish farm,” said Sánchez.

He added that, in a second trial, the product showed a protective response of more than 30 days after the last intake, a finding that supports Vitalice's potential as a complementary tool in the integrated management of Caligus.

No fasting, no stress

“In addition to reducing the number of egg-bearing females, there is a significant operational advantage: it is administered orally, without fasting periods, does not cause the stress of bathing treatments, and maintains its effectiveness even after the last dose. We believe it is a high-value-added alternative for the national salmon farming industry, contributing to a reduction in the use of antiparasitic drugs, strengthening animal welfare, improving production indicators, and allowing us to move towards sustainable production certifications.”

Sánchez indicated that the company decided to launch Vitalice in the Magallanes region as a way to reaffirm its commitment to the region, which has established itself as one of the most promising areas for salmon farming in Chile. 

He explained that lower sea temperatures had historically kept parasite loads on Magallanes fish farms well below those recorded further north, in Los Lagos and Aysén. However, climate change, record high sea temperatures, and the developing El Niño climate event have created environmental conditions that favour the establishment of sea lice in the region and pose a new challenge for local aquaculture.

Time to prevent is now

According to data from state aquaculture agency Sernapesca, in 2024 eight salmon farming concession groups reported the presence of Caligus, with a regional maximum of 0.10 ovigerous females (OF) per fish. In 2025, there were 10 concession groups with lice and the maximum rose to 0.30 OF. At the same time, the highest weekly prevalence in farms with loads of three or more OF decreased from 5.56% to 2.60%.

“In other words, there is no generalised increase in loads, but the parasite has spread to more areas and has become a permanent health challenge in the region. Changes in susceptibility to traditional antiparasitic drugs are also being observed. Therefore, this period of low load is the window of opportunity to anticipate: the time to prevent is now,” concluded Sánchez.