[quotes]
2. The definition of probionts
Elie Metchnikoff’s work at the beginning of this century is regarded as the first
research conducted on probioticsFuller, 1992.. He described them as Amicrobes
ingested with the aim of promoting good healthB. This same definition was modified to
Aorganisms and substances which contribute to intestinal microbial balanceB Parker,
1974., and later by Fuller1989. to Aa live microbial feed supplement which beneficially
affects the host animal by improving its intestinal microbial balanceB. These
definitions originally applied to farm animalsruminants, poultry and pigs.or humans,
since the first studies were carried out in these species.
Probiotics are now also being used in aquaculture and therefore, the definition may
have to be modified. In aquatic animals, not only the digestive tract is important but also
the surrounding water. Gatesoupe1999.defines probiotics as Amicrobial cells that are
administered in such a way as to enter the gastrointestinal tract and to be kept alive, with
the aim of improving healthB. Gram et al.1999.broadened the definition by removing
the restriction to the improvement to the intestine: Aa live microbial supplement which
beneficially affects the host animal by improving its microbial balanceB.
Biological control has been described as the utilisation of natural enemies to reduce
the damage caused by noxious organisms to tolerable levelsDebach and Rosen, 1991.
or more precisely, the control or regulation of pest populations by natural enemies
Smith, 1919.. Strictly speaking, a probiotic ought not to be classified as a biological
control agent, since a probiotic microorganism does not necessarily attack the noxious
agentpathogen.. It need not necessarily be a natural enemy of the pathogen, but it
merely prevents damage to the host caused by the pathogen, usually through competition
but at most, it may produce substances that inhibit the growth or attachment of the
harmful microorganism. Neither should probiotics be classified as growth promoters,since their action is not confined to improved growth but is associated with a general
improvement in health.
The microbial community inside the gut of some animals confers some degree of
resistance to or protection against diseaseFox, 1988.. In natural populations of aquatic
animals, the microflora of the gut might reflect that of the aquatic environment.
However, in massive artificial larval cultures, the balance can be altered by the use of
disinfected water, microalgae, Artemia nauplii, rotifers, and antibacterials. As a result, a
protective microbial community may not develop either in the environment or the
digestive system of the larvae. The postlarvae reared in a relatively sterile environment
of a hatchery do not grow well and show poor survival when they are exposed to the
complex microbial populations of the nursery or grow-out ponds. They are particularly
susceptible to diseases when exposed to environmental stress and potentially pathogenic
bacteria.[/quotes]
Đây là phần mình nói tới.Tuy tiêu đề là định nghĩa về Probionts,nhưng nó lại nói về probiotic.Nên mình không hiểu mối liên hệ giữa 2 cái đó là sao .
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