Search

Abstract The study was carried out to evaluate wedge wire screen as a potential tool for collecting fish faeces from the tank outlet water. Apparent digestibility (AD) estimates of carbon (AD C), nitrogen (AD N), sulphur (AD S), organic material (AD ORG) and individual amino acids obtained by the wire screen were compared with stripping. Three diets, with fishmeal, soybean meal (SBM) or rapeseed meal (RSM) as main protein source were extruded and fed to triplicate groups of 120-g rainbow trout (Oncorhynchus mykiss). Faeces were obtained by gentle stripping from the distal abdomen, and by collection from a wedge wire screen 15, 30, 60, 120 and 240 min post feeding. AD ORG , AD N and AD S obtained by collection on the screen were significantly (P <.05) higher than those obtained by stripping, except for some values for AD C. Differences in AD between stripping and faeces collected with the wire screen were lower than reported for other methods of collection from water media. Most of the increase in AD of nutrients for wedge wire screen occurred during the first 15 min after defecation. The AD ORG , AD C , AD N and AD S were lowest in the RSM diet. The AD of amino acids followed the same pattern as AD N. AD S in the rapeseed diet was particularly low (54.7%), compared to the fishmeal (72.4%) and SBM diet (70.1%). In addition to AD of cysteine, low digestibility of glucosinolates, its degradation products and other sulfonated components are likely reasons for the low AD S. Faeces from the RSM based diet had higher dry matter (DM) concentration than the SBM based diet. Faecal DM recovery for SBM was lowest among the diets for both collection methods. The low DM recovery for the SBM faeces did not affect AD estimates of faeces at the different time intervals, possibly due to simultaneous leakage of nutrients and indigestible marker. In conclusion, the use of wedge wire screen for collection of faeces represents an interesting supplement to stripping. The AD estimates had low random variation and nutrient leaching during faeces collection were dependent on dietary composition. Highlights • The digestibility estimates from the wire screen had low variation within time points and dietary treatments. • Digestibility results obtained for faeces collected from water should not be used as indicator for fecal nutrient loss • Feed composition and characteristics play a significant role in nutrient loss from faeces. [ABSTRACT FROM AUTHOR]

Abstract: Ration levels were used to determine the digestible protein (DP) and amino acids as well as digestible (DE) and metabolizable energy (ME) requirements of Atlantic salmon post-smolts for maintenance and the efficiency of utilization for gain above maintenance. The salmon (96g) were held in seawater at a temperature of 10°C and were fasted for 28days or fed incremental ration levels of a fishmeal-based diet for 51days. The composition of gain was determined by the comparative slaughter technique. The relationships between intake of digestible or metabolizable nutrients or energy and gain of those nutrients or energy were linear (R 2 ≥0.98) between zero intake and maximum voluntary intake. The DE and ME requirements for maintenance were 31.5 and 30.6kJkg−0.8 d−1, respectively, and the efficiency of utilization of DE and ME for gain were 0.80±0.01 and 0.82±0.01, respectively. The efficiency of utilization for gain of DP was 0.64±0.01 and that of the sum of digestible amino acids 0.57±0.02. The efficiency of utilization of the individual amino acids for gain varied from 0.45 for tryptophan to 0.65 for histidine. The maintenance requirement for DP was 117.5mgkg−0.7 d−1 and for digestible sum of amino acids 204.0mgkg−0.7 d−1. The maintenance requirements for the individual amino acids varied from 4.3mgkg−0.7 d−1 for methionine and tryptophan to 20.9mgkg−0.7 d−1 for leucine. The results suggest more emphasis should be directed towards determining the maintenance requirements and the efficiency of utilization for gain above maintenance for the individual amino acids and the sum of amino acids rather than for crude protein. [Copyright &y& Elsevier]

Apparent digestibility coefficients were determined for six feedstuffs, subsequent to their processing into pelleted feed for tropical freshwater catfish, Mystus nemurus (Cuvier & Valenciennes), using a reference diet and test diets composed of 70% reference diet and 30% test ingredient. It was found that most ingredients were fairly well digested except maize and chicken viscera. Digestibility coefficient for protein (P), dry matter (DM) and energy (E) were: (1) fish meal: 97.8% P, 97% DM. 77.88% E: (2) soybean meal: 86% P, 95.55% DM, 67.89% E: (3) rice bran: 81% P, 85.81% DM, 67.93% E: (4) copra meal: 79.90% P, 86% DM, 71.89% E: (5) maize: 51.93% P, 49.0% DM. 63.40% E and (6) chicken viscera: 37% P, 29% DM. 52% E. Digestibility coefficients for feedstuffs indicated that animal protein product, such as fish meal and grain by-product, such as rice bran were more digestible than starchy and fibrous feed, e.g. maize. Chicken viscera was poorly digested largely due to inefficient processing. As most feedstuffs were well digested, ingredient selection should, therefore, be based primarily on their protein content, amino acid composition and palatability. [ABSTRACT FROM AUTHOR]