Page 12 - New additives and ingredients in the formulation of aquafeeds

10 Natural growth promoters in aquaculture practices
In both industrialized and developing countries, nutrition and feeding play
a critical role in the sustained development of aquaculture, thus particular
emphasis is currently being placed on nutritional strategies and their effect
on animal health, performance, and environmental integrity. While a first
nutritional approach is the increasingly accessible information on nutrient
requirements for each of the species as well as on the more effective use of
alternative and available ingredients, a second approach is supplementation
with natural growth promoters (NGPs). Also termed non-antibiotic growth
promoters, NGPs are feed additives contemplating different categories as
salts of organic acids, probiotics, prebiotics, phytogenics or yeast. In addition
to the beneficial effects in terms of health status and performance, NGPs
supplementation does not usually bear any risk regarding bacterial resistance
or undesired residues in the edible fish product. In terms of manufacture,
worldwide aqua feed production is growing at a rate of 11.1% per year and is
expected to reach 70.9 million tones by 2020 (Tacon, 2010) thus the demand
for NGPs is expected to augment accordingly (142.000 tones of NGPs by 2020
if average inclusion is about 2 kg of NGP per ton of feed). In such market
situation, and as a leading company in NGPs manufacture, it is Norel´s
objective to develop innovative and competitive products and consequently
to provide customers with the most updated information regarding mode
of action, use and benefits. This chapter will review the characteristics and
benefits of using probiotics and organic acid salts for aquaculture practices,
specially focusing on Bacillus spp. and sodium butyrate.
Probiotics:
Bacillus spp.
A probiotic application for aquaculture practices can be defined as a live
microbial supplement that administered via feed or directly into the rearing
water provides a benefit to the animal by enhancing nutrient utilization,
health status, stress response, disease resistance and performance,
and this is partly achieved by optimizing the microbial balance within
the animals and water environment (Merrifield et al., 2010). A list of
characteristics for potential probiotic bacteria has been reported by several
authors (Farzanfar, 2006; Vine et al., 2006; Gómez and Balcazar, 2008)
and extended by Merrifield et al. (2010). Among them there are essential
properties as being a non-pathogenic microorganism and being resistant to
bile salts and low pH. Other favourable properties are adequate and rapid
growth at host rearing temperature, antagonistic properties against key
pathogens, capacity to produce extra cellular enzymes that improve feed
utilization, viability under normal storage conditions and acceptable survival
under processing conditions.
Among the different strains of probiotics used at present in aquaculture
practices, Bacillus spp. are well known due to its sporulated form that
confers easy handling, long shelf life, and convenience to be mixed with
mash when processing temperature is below 90ºC. Numerous studies have
demonstrated the beneficial effect of supplementing fish and shrimp diets
with Bacillus spp. By re-establishing a beneficial gastrointestinal micro
biota composition, this application will exert a major effect within the host
(Table 1), resulting in enhanced break down of digesta, reduced pathogenic