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Use of computer-assisted image analysis to monitor health and nutrition status in whiteleg shrimp (Penaeus vannamei) By Fabio Cervellione, Charles McGurk, Skretting ARC and Wim Van den Broeck, Ghent University

The aquaculture of penaeid shrimp has grown from its experimental beginnings three decades ago into a major industry. Almost from the start, diseases and adverse environmental conditions were recognized as threats to the shrimp industry, causing serious economic losses. Feeding strategies form an important part of modern farm management. Feed manufacturers invest in R&D to develop and offer new feeds and feeding solutions aimed at helping shrimp farming to grow, and to support against emerging health issues and adverse environmental conditions. Current methods to assess health and nutritional status in shrimp mainly rely on clinical examination followed by laboratory investigations and evaluation of growth performance. One of the key indicators of health in shrimp is the perigastric organ (formerly known as the hepatopancreas), making it one of the most useful to examine. The perigastric organ is the site of synthesis and secretion of digestive

enzymes, digestion and nutrients absorption, reserve storage and detoxification. The perigastric organ is bilobed and composed of many blindly ending tubules, which wrap over the dorsal and lateral sides of the posterior part of the stomach and the anterior part of the midgut. It is the principal organ of the digestive tract and vulnerable to pathophysiological changes.

Feeding regime affects the perigastric organ. Under starvation and refeeding conditions, beneficial lipid droplets are rapidly depleted and haemocytes (comparable to the white blood cells in mammals) are recruited to mitigate degenerative processes and inflammation occurring in the organ. Haemocyte infiltration in the intertubular spaces of the perigastric organ is also observed in instances of tissue damage (traumatic or due to infection), toxicity and environmental stress. In current practice, histological analysis of the perigastric organ is based on qualitative features interpreted by

pathologists. Pathologists’ quantification is generally time-consuming and poorly objective, with significant discrepancies in scoring results reported between observers. This has motivated the development of computer-assisted image analysis (CAIA) methods for producing unbiased, objective, reproducible, and reliable data. The basic principle of automated image analysis for histology is the use of a series of mathematical algorithms to process images, enabling the segmentation of picture elements into regions of interest based on their colour, texture and/or context. CAIA is currently used by Skretting Aquaculture Research Centre (ARC) to investigate a number of organs (gills, gut and skin) across various fish species.

The success of these methods in fish recently led to the development of a semi-quantitative histological method to monitor health and the nutritional status in whiteleg shrimp using CAIA on microscopic sections of the perigastric organ. After the optimization of fixation

Aquafeed vol 9 issue 2 2017  

Aquafeed magazine is focused on advances in feed formulation and processing for aquatic species. It is the quarterly magazine of Aquafeed.co...

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