EFFECT OF PROBIOTIC AND ZINC IN GUT INTEGRITY OF PRE AND POST WEANED PIGLETS: AN IMMUNOMORPHOLOGICAL AND BIOMOLECULAR ANALYSIS
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Date
2019-07
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College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati
Abstract
Present study was undertaken to elaborate alteration of histomorphological,
histochemical, ultrastructural, immunofluorescence, gut microbiota, cytokine gene
profile and brush border enzyme activity of histocompartments of small intestine in
control (basal diet) and treatment (basal diet + probiotic + zinc) group piglets during pre
and post-weaned period. This study was assumed to understand the effect of probiotic
and zinc on gut digestibility and immunity compared to the control piglets so that the
productivity of this important species of farm animal could be enhanced. Besides, this
information was assumed to help to control the post-weaning diarrhoea in piglets that
causes significant economic losses in pig production.
Eighteen (18) numbers of apparently healthy Large White Yorkshire piglets,
irrespective of their sex were utilized in the present study. These piglets were selected
from three litters (6 piglets from one litter) and were divided into control (basal diet) and
treatment (basal diet + probiotic + zinc) groups, consisting of 3 animals in each group.
The probiotic (dosed daily with 1.25 109 CFU/gm) and zinc (ZnO dosed daily with
2000 ppm) was supplemented orally to the treated piglets from birth to 10 days of age.
The weaning of the piglets was done at 28 days. The animals were sacrificed at day 20,
day 30 and day 60 from both the groups. The histomorphological, ultrastructural,
histoenzymatic, immunofluorescence and cytokine gene expression were performed to
study the alteration in treatment group of piglets. Besides, examination of brush border
enzyme activity was done to evaluate the conversion of disaccharide into
monosaccharide in these two groups of piglets.
The villus and crypt morphometry revealed higher villus height, villus width,
crypt depth, crypt width, villus enlargement factor and crypt enlargement factor, and
lower villus crypt ratio in treatment group of piglets. This might indicate greater
absorptive capacity of available nutrients and higher epithelial turn-over rate to
compensate losses in height of villi in treated piglets especially during early postweaning
period.
In the mucosa of villus and crypt, the number of goblet cells, argentaffin cells and
tuft cells were increased in treatment group of piglets. These findings might be
concluded with better enhancement of epithelial barrier, higher production of
gastrointestinal hormones, better microenvironment of gut and defense mechanism
which resulted in effective immunity and digestibility in this group of piglets.
In the lining epithelium of small intestine, the number of intraepithelial
lymphocytes (IEL) was higher in treatment group piglets that could be the result of a
nonspecific stimulation of the local immune system possibly by certain antigens of
probiotic bacteria. The increased number of IEL might be an indicative of more mature
and efficient adaptive immune response in piglets fed with probiotic and zinc than the
control animal.
In the histotopographic areas, the CD4+ cells, CD8+ cells, IgA+ cells and IgM+
cells were increased in treatment group of piglets. These findings might be interpreted
with more production and secretion of secretory IgA, enhancing defense against
pathogens, maintenance and enhancement of epithelial cell integrity and production of
more immunoglobulin to ensure a fast reaction against potential pathogens. These might
led to better mucosal immunity in the probiotic and zinc treated piglets.
In the treatment group of piglets, the brush border enzyme activity was higher to
convert their respective substrates into glucose that might be indicative of more
absorption of glucose from the available carbohydrate present in the intestine, and
resulted with better growth and development in this group of piglets.
The increased activity of acid and alkaline phosphatase in treated piglets might be
correlated with higher secretion of glands and greater absorptive capacity of enterocytes.
Similarly, higher ATPase and non-specific esterase activities might be indicative of more
concentration of B and T cells in follicular and interfollicular areas of PP in treatment
group of piglets, respectively.
The cultivable cell counts of lactic acid bacteria were higher in treatment group
of piglets. These more number of beneficial microbiota might reduce the pathogenic
bacterial load in the small intestine and provide a healthy environment for better
digestion and immunity in treatment group of piglets especially in early post-weaning
period.
The marginal up-regulation of cytokine expression of TNF-α, IL-1β and IL-6
transcripts in treatment group of piglets might have resulted in the stimulation of innate
immune cells to eradicate microbes and enhancement of IgA B-cell population in the
young ones and increased epithelial cell turn-over.
The down-regulation of cytokine expression of IL-8, IL-12 and IL-18 transcripts
in treatment group of piglets possibly lead to decreased activity of NK cells and CD8+
cytotoxic T lymphocytes which was an indicative of lesser infections associated with
intracellular pathogens and presence of healthy intestinal epithelial cells in the gut.