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This study evaluated the growth and gut performance of shrimp fed three isonitrogenous diets (37% crude protein) with varying inclusions of fish meal (FM) and soybean meal (SBM): F1 (27.5% FM), F2 (10% FM + 23.5% SBM), and F3 (38% SBM). Over a 28-day period, feed intake, feed conversion ratio (FCR), and survival rates showed no significant differences among the groups. However, shrimp fed F2 and F3 exhibited significantly higher weight gain and average daily growth (ADG) compared to those fed F1 (P < 0.05). Gut performance analysis revealed that F3 consistently had the highest gut passage time (GPT), while F1 had the lowest. By day 28, shrimp fed F2 displayed elevated gut retention time (GRT). F1-fed shrimp showed a high gut passage rate (GPR), whereas F3-fed shrimp had a low GPR until day 21, with differences becoming negligible by day 28. Histological examination of the hepatopancreas revealed an increased R-cell population in shrimp fed F3. These findings highlight the adaptability of shrimp to different dietary compositions and underscore the importance of considering multiple factors when assessing the impacts of feed on growth and physiology., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

White feces syndrome (WFS) in cultivated shrimp is characterized by white shrimp midguts (intestines) and white fecal strings that float as mats on pond surfaces. The etiology of WFS is complex, but one type called EHP-WFS is associated with the microsporidian Enterocytozoon hepatopenaei (EHP). The hepatopancreas (HP), midgut and fecal strings of EHP-WFS shrimp exhibit massive quantities of EHP spores together with mixed, unidentified bacteria. In EHP-WFS ponds, some EHP-infected shrimp show white midguts (WG) and produce white feces while other EHP-infected shrimp in the same pond show grossly normal midguts (NG) and produce no white feces. We hypothesized that comparison of the microbial flora between WG and NG shrimp would reveal probable combinations of microbes significantly associated with EHP-WFS. To test this, we selected a Penaeus vannamei cultivation pond exhibiting severe WFS and used microscopic and microbial profiling analyses to compare WG and NG samples. Histologically, EHP was confirmed in the HP and midgut of both WG and NG shrimp, but EHP burdens were higher and EHP tissue damage was more severe in WG shrimp. Further, intestinal microbiomes in WG shrimp were less diverse and had higher abundance of bacteria from the genera Vibrio and Propionigenium. Propionigenium burden in the HP of WG shrimp (9364 copies/100 ng DNA) was significantly higher (P = 1.1 × 10 -5 ) than in NG shrimp (12 copies/100 ng DNA). These findings supported our hypothesis by revealing two candidate bacterial genera that should be tested in combination with EHP as potential component causes of EHP-WFS in P. vannamei., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Enterocytozoon hepatopenaei (EHP) is an obligate intracellular parasite causing hepatopancreatic microsporidiosis (HPM) in cultivated shrimp in Asian countries. One strategy to control EHP is to identify and eliminate biological reservoir(s) in shrimp ponds. Several marine and brackish-water organisms, including false mussels (Mytilopsis) have been reported to test positive for EHP using the PCR method. Thus, we tested Thai false mussel Mytilopsis leucophaeata collected from the 6 ponds with EHP-infected shrimp for the presence of EHP using SWP-PCR. Results revealed the sampled mussels from all 6 ponds were PCR positive. Subsequent bioassays were carried out to study EHP transmission between mussels and shrimp. Firstly, the naïve mussels were cohabitated with EHP-infected shrimp and all mussels were SWP-PCR positive at day 20 post cohabitation. One batch of such PCR-positive mussels was transferred for cohabitation with naïve shrimp and 37.5% EHP-positive shrimp were observed within 10 days. Tissue analysis of the SWP-PCR-positive mussels using light microscopy, in situ hybridization technique and electron microscopy did not confirm EHP infection. In summary, there was no evidence demonstrating that Mytilopsis leucophaeata was itself infected with EHP. However, the false mussels were apparently capable of carrying infectious spores for some period after ingestion and serving as a mechanical or passive carrier. The results support previous reports warning of the danger of feeding living or fresh bivalves to broodstock shrimp in hatcheries or shrimp in rearing ponds without prior heating or freezing., (Copyright © 2021 Elsevier Inc. All rights reserved.)