Validation of a methodology for measuring nutrient digestibility and evaluation of commercial feeds for channel catfish

Abstract

Channel catfish, a major freshwater aquaculture species in the US, is also farmed in Southern Brazil. However, apparent digestibility coefficients (ADC) of nutrients in commercial feeds available in Brazil for the species are not known. This study aimed at optimizing a methodology for fecal collection and determination of apparent nutrient digestibility for catfish. Pilot trials were carried out to establish gastrointestinal transit, fish density, and time interval between fecal collections. Gastrointestinal transit of dry feed for catfish varied from 11h30 to 10h30 for 100 and 172-g fish, respectively. Average dry weight of feces produced along a six day period by 99-g fish was 0.54 g, regardless of stocking density (10, 15 or 20 fish per 98-L cage; p > 0.05). Described methodology allowed the collection of average 10.80 g feces per tank (dry weight) in three days. Feces collected at 1, 6 or 12 h had increased protein digestibility from 1 to 12 h, that is, there was increased protein leaching as the time of feces exposure to water increased. Fecal collection was optimized at 20 fish per tank and 6 h interval between collections. ADC of protein, energy, and dry matter of four commercial feeds for catfish using the indirect method with the addition of 0.5% of Cr 2 O 3 as an inert maker was also evaluated. Crude protein contents of commercial feeds matched manufacturer's specifications but did not yielded the 28% digestible protein required for adequate channel catfish growth. The digestible protein of commercial feeds ranged from 23.3% to 25.6% and digestible energy ranged from 1177 to 1249 kJ 100 g -1 feed. It is instrumental measuring nutrient digestibility when evaluating commercial feeds. Key words: nutrient availability, fish nutrition, siluriform fish, channel catfish Validação de um método para medir a digestibilidade de nutrientes e avaliação de rações comerciais para catfish RESUMO: O catfish americano, espécie aquícola importante nos Estados Unidos, também é produzido no sul do Brasil. Entretanto, a digestibilidade dos nutrientes das rações disponíveis no Brazil não é conhecida. Nesse estudo otimizou-se a coleta de fezes e a determinação do coeficiente de digestibilidade aparente (CDA) para a espécie. Ensaios pilotos foram conduzidos para determinação do tempo de passagem do alimento no trato digestório, densidade dos peixes e intervalo entre coletas de fezes. O tempo de passagem variou de 11h30 a 10h30 em peixes com peso médio de 100 e 172 g, respectivamente. O peso médio (base seca) das fezes produzidas por peixes (peso médio 99 g), em seis dias, foi 0.54 g, independentemente de a densidade ser 10, 15 ou 20 peixes por gaiola (p > 0.05). Com esta metodologia foi possível coletar 10.80 g de fezes (base seca) por tanque em três dias. A digestibilidade da proteína aumentou com intervalos de coleta de fezes de 1, 6 e 12 h, indicando aumento na lixiviação deste nutriente à medida que aumentou o tempo de exposição das fezes à água. A coleta de fezes foi otimizada com 20 peixes por tanque e com 6 h ...

Digestibility of feed ingredients for the striped surubimPseudoplatystoma reticulatum

“…Juvenile striped surubim P. reticulatum (82.4 ± 17.8 g; 23.0 ± 1.6 cm L T ) was adapted to laboratory conditions for 30 days and then stocked in 21, 80‐L cylindrical plastic cages (five animals per cage) housed in 1000‐L plastic tanks, and fed manually to apparent satiation twice a day (20h00min and 22h00min). Two hours after last meal, fish were transferred to cylindrical, conical‐bottomed aquaria (200 L) under aeration and continuous water exchange, coupled to refrigerated plastic bottles for faeces collection by sedimentation; faecal material was collected twice (6h00min and 12h00min) according to recommendation of Kitagima & Fracalossi ().…”

Gastrointestinal transit of extruded or pelletized diets in pacu fed distinct inclusion levels of lipid and carbohydrate

“…GITT's mathematical profile is related to the excretion curve (Kitagima & Fracalossi, 2010) and to the particular flow of food into a given segment of the digestive tract (Oliveira et al, 2007). However, it is worth emphasizing that these adaptations are related to the chyme fluidity in the digestive tract, which depends on the diet composition and on the amount of ingested food.…”

“…These variables may change from one study to another. Chyme fluidity also depends on gastric secretions and the degree of digestion in the digestive tract (Kitagima & Fracalossi, 2010).…”

“…agropec. bras., Brasília, v.49, n.11, p.829-835, nov. 2014 DOI: 10.1590/S0100-204X2014001100001 fed diets which remain in the digestive tract for short periods may have low-digestion and absorption rates of nutrients (Kitagima & Fracalossi, 2010). Besides, feed permanence for long time in the digestive tract may decrease animal performance, impairing digestion or absorption, for avoiding a free space to be stuffed by new feed (Kubtiza, 2013).…”

Crescimento, digestibilidade e resistência à infecção por patógeno em tilápia-do-nilo alimentada com probióticos

“…bras., Brasília, v.48, n.8, p.863-870, ago. 2013 DOI: 10.1590/S0100-204X2013000800008 descrita por Kitagima & Fracalossi (2010), com apenas uma modificação: os animais permaneceram nos mesmos tanques durante a alimentação e a coleta de fezes. Cada coleta de fezes era precedida de uma limpeza rigorosa das paredes do tanque, bem como de uma troca de 90% da água, para evitar contaminação das fezes com restos de ração e filme bacteriano formado nas paredes dos tanques.…”