Dietary supplementation with Bacillus subtilis LT3‐1 enhance the growth, immunity and disease resistance against Streptococcus agalactiae infection in genetically improved farmed tilapia, Oreochromis niloticus

Abstract

A feeding trial was conducted to investigate the effect of different levels of Bacillus subtilis LT3‐1 in diets on growth, immune parameters, intestinal morphology and disease resistance in genetically improved farmed tilapia, Oreochromis niloticus. Fish (46.91 ± 0.17 g) were fed with a basal diet supplemented with B. subtilis LT3‐1 at 0 (B0), 3.8 × 1010 (B1), 7.6 × 1010 (B2), 1.14 × 1011 (B3) and 1.52 × 1011 (B4) CFU kg−1 for 6 weeks. The results showed that the weight gain of fish in B1 group was significantly enhanced compared to that in B0 group (p < 0.05). The addition of B. subtilis significantly affected serum biochemical indices (total protein, albumin, aspartate aminotransferase, alkaline phosphatase). Besides, the haematocrit, total counts of red and white blood cells, as well as the serum catalase and lysozyme activities, were increased, whereas the serum malondialdehyde, the serum immunoglobulin M and complement three contents were reduced. Parameters for intestinal morphology suggested a healthier intestine for the fish fed B. subtilis‐supplemented diets than fish fed the control diet. The survival rate after Streptococcus agalactiae challenge increased in tilapia fed with B. subtilis. The present study demonstrated B. subtilis can effectively improve growth, immunological status and resistance against S. agalactiae infection in tilapia farming.

Dietary Bacillus NP5 supplement impacts on growth, nutrient digestibility, immune response, and resistance to Aeromonas hydrophila infection of African catfish, Clarias gariepinus

“…The same results demonstrated by Ahmadifar et al (2020) who reported the addition of probiotic Pediococcus pentosaceus 10 8 -10 9 CFU g -1 increased the general hematocrit value compared to the controls in carp. Zhu et al (2019) also reported that the hematocrit value in tilapia given probiotic B. subtilis LT3-1 was increased compared to the controls.…”

“…Previous studies showed that probiotics supplementation in aquaculture results in increasing growth and feed digestibility. Probiotics increase digestive enzyme activity (Enferadi et al 2018;Valiallahi et al 2018;Arani et al 2019), increase immunity against pathogens (Amir et al 2019;Zhu et al 2019), and improve the water quality of culture media (Elsabagh et al 2018;Kewcharoen and Srisapoome 2019).…”

A mini-review: Effect of probiotics on the growth and health of fish

“…The same thing was stated by [12] , probiotics are a substitute for antibiotics and can suppress the growth of pathogens without harming the host and the environment. Probitotics can increase the body's resistance to pathogens [13,14] and increase the activity of digestive enzymes that will affect fish growth. According to Dawood et al (2018) [15] and RingØ (2020) [16] probiotics can increase the diversity of intestinal microflora, compete with harmful microorganisms, facilitate nutrient absorption through intestinal villi, and increase the natural (innate) immunity of the fish body.…”

The effect of induced changes in gut microbiota on fish performance

“…The growth-promoting effect of Bacillus spp. on tilapia is dose dependent, for instance, dietary supply of B. subtilis at 4 × 10 7 CFU/g of feed had no effect on tilapia growth (Addo et al, 2017), while at a dosage of 10 8 CFU/g of feed or higher showed enhancement in the growth of tilapia (Mohammadi et al, 2020;Won et al, 2020;Zhu et al, 2019). Although B. subtilis can improve the growth and survival of juvenile or adult tilapia in some studies (Addo et al, 2017;Opiyo et al, 2019), dietary supplementation of Bacillus spores to 2g tilapia fry for 8 weeks did not affect their growth (Sookchaiyaporn et al, 2020).…”

“…have been widely used as probiotics in aquaculture (Kuebutornye et al, 2019). In several studies, dietary supplementation of B. subtilis in tilapia could increase the immune response and resistance to pathogen infection (Liu et al, 2017;Won et al, 2020;Zhu et al, 2019). In previous studies, dietary supplementation of B. subtilis decreased the bacterial diversity in the gut of gilthead sea bream and reduced the bacterial counts in the gut of rainbow trout (Cerezuela et al, 2013;Newaj-Fyzul et al, 2007).…”