Effects of Lactobacillus Strains as a Probiotic and a Hypolipidaemic Agent for Chickens
In recent years, there has been considerable interest in the beneficial effects of probiotics (direct-fed microbials, which include Lactobacillus) to modulate the lipid metabolism. However, the mechanism(s) involved remains unclear. A series of experiments was carried out to investigate the abili...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2003
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/7963/1/IB_2003_2.pdf |
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| Summary: | In recent years, there has been considerable interest in the beneficial effects
of probiotics (direct-fed microbials, which include Lactobacillus) to modulate the
lipid metabolism. However, the mechanism(s) involved remains unclear. A series of
experiments was carried out to investigate the ability of 1 2 Lactobacillus strains to
deconj ugate bile salts and to remove cholesterol in vitro, and to assess their potential
as a pro biotic and as a hypolipidaemic agent for broilers and laying hens. Bile salt
hydrolase (BSH) activity (resulting in bile salt deconjugation) of intestinal bacteria
is closely linked to the lowering of cholesterol. The results of the in vitro studies
showed that all the 1 2 Lactobacillus strains could deconjugate sodium glychocholate
(GCA) and sodium taurocholate (TCA) bile salts, and all the strains, except L.
fermentum I 24, had a higher affinity for GCA. However, only eight strains could
deconjugate sodium taurodeoxycholate (TDCA). This indicates that the BSH of the
Lactobacillus strains is substrate specific. The 1 2 Lactobacillus strains showed
significant differences in their ability to reduce cholesterol from the growth medium
(27 to 85 %) with or without bile salt, indicating that bile salt is not a prerequisite for
the removal of cholesterol. Lactobacillus acidophilus I 1 6, L. crispatus I 1 2, L. brevis C 1 7 and I 2 1 1 , and L. Jermentum I 24 and I 25 removed cholesterol from the
growth medium mainly through assimilation of cholesterol into the cells. On the
other hand, L. brevis C 1 , C 1 0, I 23 and I 2 1 8, and L. Jermentum C 1 6 removed
cholesterol through both assimilation and co-precipitation of deconjugated bile salt
with cholesterol at low pH. The Lactobacillus strains assimilated more esterified
than non-esterified cholesterol and the assimilated cholesterol was tightly bound to
the cells. Cells grown in the presence of cholesterol were more resistant to lysis by
sonication than when grown in its absence, suggesting a possible alteration of the
cell wall or membrane by the assimilated cholesterol. Cholesterol removal by the
Lactobacillus strains was also affected by Tween 80.
The feeding trials showed that the supplementation of a mixture of the 1 2
Lactobacillus cultures (LC), as a probiotic for broilers, significantly improved
growth equivalent to that provided by the antibiotic, oxytetracycline, but the feed
conversion ratio was better in LC-fed broilers. The supplementation of LC also
significantly lowered the total cholesterol, low density lipoprotein cholesterol and
triglycerides of the serum; the cholesterol of the carcass and liver; abdominal fat
deposition; and fat contents of the liver, muscle and carcass of broilers; but there
was little effect on the fatty acid compositions of the liver, muscle and carcass.
In laying hens, the supplementation of LC improved the feed efficiency and
hen-day egg production during the early stage of the laying cycle, and increased egg
weight and influenced a shift from small and medium to large and extra large eggs
throughout the laying cycle. However, LC had very little effect on improving the
fatty acid composition, and the cholesterol and total fat contents of eggs. |
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