AUTHOR=Xia Miao , LI Chong , Wu Diange , Wu Fengyang , Kong Lingchang , Jia Zifan , Han Wenxiao , Chen Saijuan , Fang Wei , Liu Yajuan , Chen Baojiang 

TITLE=Benefits of heat-killed Lactobacillus acidophilus on growth performance, nutrient digestibility, antioxidant status, immunity, and cecal microbiota of rabbits

JOURNAL=Frontiers in Veterinary Science

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2024.1361908

DOI=10.3389/fvets.2024.1361908

ISSN=2297-1769

ABSTRACT=<sec><title>Introduction</title><p>Heat-killed probiotics, as a type of inactivated beneficial microorganisms, possess an extended shelf life and broader adaptability compared to their live counterparts. This study aimed to investigate the impact of heat-killed <italic>Lactobacillus acidophilus</italic> (<italic>L. acidophilus</italic>, LA) - a deactivated probiotic on the growth performance, digestibility, antioxidant status, immunity and cecal microbiota of rabbits.</p></sec><sec><title>Methods</title><p>Two hundred weaned Hyla rabbits were randomly allocated into five equal groups (CON, L<sub>200</sub>, L<sub>400</sub>, L<sub>600</sub>, and L<sub>800</sub>). Over a 28-day period, the rabbits were fed basal diets supplemented with 0, 200, 400, 600, and 800 mg/kg of heat-killed LA, respectively.</p></sec><sec><title>Results</title><p>Results revealed a significant reduction in the feed-to-gain ratio (F/G) in the L<sub>600</sub> and L<sub>800</sub> groups (<italic>p</italic> &lt; 0.05). Additionally, the L<sub>800</sub> group exhibited significantly higher apparent digestibility of crude fiber (CF) and crude protein (CP) (<italic>p</italic> &lt; 0.05). Regarding digestive enzyme activities, enhanced trypsin and fibrinase activities were observed in the L<sub>600</sub> and L<sub>800</sub> groups (<italic>p</italic> &lt; 0.05). Concerning the regulation of the body’s antioxidant status, the L<sub>800</sub> group demonstrated elevated levels of superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in both serum and ileal tissue (<italic>p</italic> &lt; 0.05). In terms of immune capacity modulation, serum tumor necrosis factor-α (TNF-α) levels were significantly lower in the L<sub>600</sub> and L<sub>800</sub> groups (<italic>p</italic> &lt; 0.05), while immunoglobulin A (IgA) and immunoglobulin M (IgM) levels were higher (<italic>p</italic> &lt; 0.05). Additionally, the L<sub>800</sub> group exhibited a substantial increase in secretory immunoglobulin A (SIgA) levels in the intestinal mucosa (<italic>p</italic> &lt; 0.05). In comparison to the CON group, the L<sub>800</sub> group exhibited a significant increase in the relative abundance of <italic>Phascolarctobacterium</italic> and <italic>Alistipes</italic> in the cecum (<italic>p</italic> &lt; 0.05). <italic>Phascolarctobacterium</italic> demonstrated a positive correlation with SIgA (<italic>p</italic> &lt; 0.05), IgM (<italic>p</italic> &lt; 0.01), and Glutathione peroxidase (GSH-Px) (<italic>p</italic> &lt; 0.05), while displaying a negative correlation with TNF-α levels (<italic>p</italic> &lt; 0.05). Concurrently, Alistipes exhibited positive correlations with IgA (<italic>p</italic> &lt; 0.05), IgM (<italic>p</italic> &lt; 0.05), SIgA (<italic>p</italic> &lt; 0.01), GSH-Px (<italic>p</italic> &lt; 0.05), SOD (<italic>p</italic> &lt; 0.05), and T-AOC (<italic>p</italic> &lt; 0.01), and a negative correlation with TNF-α (<italic>p</italic> &lt; 0.05).</p></sec><sec><title>Discussion</title><p>In conclusion, the dietary incorporation of 600 mg/kg and 800 mg/kg of heat-killed LA positively influenced the growth performance, nutrient digestibility, antioxidant status, immune capacity and cecal microbiota of rabbits. This highlights the potential benefits of utilizing heat-killed probiotics in animal nutrition.</p></sec>