Figure 3
Impact of V. harveyi strain 1 on feed pellets and on Li. vannamei. The feed pellets were treated with a suspension of V. harveyi strain 1 after pre-mixing with (suppressive feed) or without La. plantarum L75a-fermented broth. (a) Impact of V. harveyi strain 1 on the bacterial cell density in feed pellets, which was determined on TCBS agar every half hour in a duration of 2 h. *Statistically significant difference compared with the corresponding suppressive feed treatment scored at the same time. (b) Bacterial cell density in the feces and intestine of Li. vannamei after 3 h of feeding (left, the second feeding test) and in the intestine, muscle and hepatopancreas after 4 days of feeding (right, the third feeding test), which was determined on TCBS agar. The dotted line separated the results from the two independent tests. (a) and (b) share the same legends. (c) The health status of Li. vannamei fed with V. harveyi strain 1-treated feed for 4 days (the third feeding test): the diseased Li. vannamei (fed without La. plantarum supplementation, lower image) exhibited acute whitish-opaque muscle necrosis, while the shrimp fed with the suppressive feed (with La. plantarum supplementation, upper image) possessed clear and transparent muscle. These muscle samples were also determined for the percentage of abundance of bacterial species based on the 16S rRNA gene amplicon sequencing (d); the detected species without designated species names and/or with mean percentage lower than 3% were not shown; the first and second numbers in the legend represent the percentage of abundance of the corresponding species detected in the muscle of Li. vannamei fed with the suppressive feed and V. harveyi strain 1-treated diets, respectively. Error bars represent S.E.M. (N = 9 (a), 8 (b) and 3 (d)).
