Effect of Fishmeal Content in the Diet on the Growth and Sexual Maturation of Olive Flounder (Paralichthysolivaceus) at a Typical Fish Farm

Investigating the effects of Carpesii fructus extract on the liver transcriptome of olive flounder (Paralichthys olivaceus) as a potential antiparasitic agent

Olive flounder (Paralichthys olivaceus), a popular aquaculture species, is plagued by the disease scuticociliatosis caused by Miamiensis avidus, which has a high mortality rate and is typically treated with chemicals such as formalin and hydrogen peroxide. However, Carpesii fructus extract has shown potential as a natural therapeutic agent by reducing the motility of M. avidus. However, despite its potential importance, the effect of the extract on fish metabolism remains unknown. In this study, the effect of Carpesii fructus extract and formalin on fish metabolism was analysed by whole transcriptome analysis in the liver of P. olivaceus. A total of 37,796 transcripts were generated and differential expression genes (DEGs) were identified in the liver of P. olivaceus treated with Carpesii fructus extract or formalin. In addition, functional analysis of DEGs between treatment groups was presented using Gene Ontology. These results will be crucial for the study of scuticociliatosis in various fish species, including P. olivaceus, and for the development of therapeutic agents for other diseases.

The Photoperiod-Driven Cyclical Secretion of Pineal Melatonin Regulates Seasonal Reproduction in Geese (Anser cygnoides)

The photoperiod is the predominant environmental factor that governs seasonal reproduction in animals; however, the underlying molecular regulatory mechanism has yet to be fully elucidated. Herein, Yangzhou geese (Anser cygnoides) were selected at the spring equinox (SE), summer solstice (SS), autumn equinox (AE), and winter solstice (WS), and the regulation of seasonal reproduction via the light-driven cyclical secretion of pineal melatonin was investigated. We show that there were seasonal variations in the laying rate and GSI, while the ovarian area decreased 1.5-fold from the SS to the AE. Moreover, not only did the weight and volume of the pineal gland increase with a shortened photoperiod, but the secretory activity was also enhanced. Notably, tissue distribution further revealed seasonal oscillations in melatonin receptors (Mtnrs) in the pineal gland and the hypothalamus-pituitary-gonadal (HPG) axis. The immunohistochemical staining indicated higher Mtnr levels due to the shortened photoperiod. Furthermore, the upregulation of aralkylamine N-acetyltransferase (Aanat) was observed from the SS to the AE, concurrently resulting in a downregulation of the gonadotrophin-releasing hormone (GnRH) and gonadotropins (GtHs). This trend was also evident in the secretion of hormones. These data indicate that melatonin secretion during specific seasons is indicative of alterations in the photoperiod, thereby allowing for insight into the neuroendocrine regulation of reproduction via an intrinsic molecular depiction of external photoperiodic variations.

Multifarious feed additives on lamb performance on Kuwait farms

Background and Aim

A change in the livestock feeding strategy is of utmost importance for the stability of animal health and sustainable livestock productivity to overcome the problem of subsiding the environmental effects of sheep production. Supplementing dietary feed with safe and efficient additives provides optimal animal performance and maximizes productivity. This study aimed to assess the effects of adding various feed additives to lamb rations for optimizing feed efficiency in weaned lambs for meat production in Kuwait.

Materials and Methods

The feed additives, namely, ammonium chloride, urea, algae, fishmeal, and humic acid, were investigated on the physical performance of lambs for their effect on body weight, length, height, and waist length. The total feed consumption rate and feed efficiency were also measured. Each treatment comprising five healthy lambs was randomly allocated into six treatments comprising 30 lambs. The six treatments were the basal ration supplemented with ammonium chloride (50-100 g/day/head), urea (30 g/day/head), fishmeal (35 g/day/head), algae (Spirulina platensis) powder (50 g/day/head), humic acid (2.5 g/day/head), control group with only basal ration. The study was conducted for around 27 months and the data were recorded once in 2 weeks.

Results

The results indicated a positive elevation in the physique of lambs with all tested additives, showing an affirmative insignia for lamb fattening. The growth parameters in terms of augmented length, height, and waist length of lambs' bodies amplified significantly with ammonium chloride and fishmeal supplement, while the other additives reported a non-significant increment. The feed consumption was significantly elevated for ammonium chloride, algae, and fishmeal supplementation, while humic acid was recorded the least. Concerning feed efficiency of young lambs, fish meal and ammonium chloride were reported best, followed by urea. In contrast, algae and humic acid exhibited a non-significant effect on feed efficiency.

Conclusion

This study exposed noteworthy influence on a lamb body's performance with the addition of fish meal and ammonium chloride in lamb rations, trailed by urea and algae.

Effects of Decreasing Fishmeal as Main Source of Protein on Growth, Digestive Physiology, and Gut Microbiota of Olive Flounder (Paralichthys olivaceus)

Simple Summary

The demand for fishmeal is increasing due to aquaculture development, but the supply is unstable. This indicates the need to reduce the fishmeal content in the feed and develop an optimal fish-feed formulation through substitutes. However, most studies on reducing fishmeal content in feed were conducted at the laboratory level. In this study, the application of a low-fishmeal diet as feed to olive flounder was evaluated in terms of growth-related factors, digestive physiology, and microbiota raised for five months in a fish farm using four feed formulations- FM70 [control (CON), 70% fishmeal], FM45 (45% fishmeal), FM35A (35% fishmeal), and FM35B (35% fishmeal + insect meal). There was no difference in growth-related factors, digestive physiology, and gut microbiota diversity compared with the CON-fed fish. Therefore, reducing the fishmeal content of the feed by up to 35% does not adversely affect growth and physiological characteristics under farm conditions.

Abstract

In olive flounder (Paralichthys olivaceus), growth performance, expression of growth-related factors, digestive physiology, and gut microbiota were assessed under farm conditions in the fish fed diets with low levels of fishmeal. Four experimental diets were prepared, FM70 [control (CON), 70% fishmeal], FM45 (45% fishmeal), FM35A (35% fishmeal), and FM35B (35% fishmeal + insect meal), and fed to the fish for five months. The CON-fed fish had the highest plasma GH, but IGF-1 and hepatic IGF-1 mRNA expression of the olive flounder fed diets with low-fishmeal levels did not significantly differ among diets. The intestinal villus length, muscular thickness, and the number of goblet cells were statistically similar, and ocular examination of hepatopancreas showed no discernable difference in all experimental diets. The chymotrypsin content of FM35B-fed fish is significantly lower, but trypsin and lipase contents are similar. The diversity of gut microbiota did not differ among groups, although the FM35B group had a higher composition of Firmicutes. Thus, a diet with reduced fishmeal content and several alternative protein sources can be used as feed ingredients in feed formulation for olive flounder reared under typical aquaculture farm conditions.