Reproductive cycle, nutrition and growth of captive blue spotted stingray, Dasyatis kuhlii (Dasyatidae)

At Burgers' Ocean 7 male and 3 female blue spotted stingrays, Dasyatis kuhlii were born over a period of 4.5 years. This paper describes the experiences of the captive breeding results of this species. The first two young died within 2 days of birth. One of them had an internal yolk sac, which may feed the young in the first few days. The other eight animals started to feed after 4 to 9 days on a variety of food types. Birth size of the young increased with increasing age of the parents. Mating occurred directly after parturition, so no seasonality could be defined. Gestation length ranged between 138 and 169 days, with a mean of 144.9±9.0 days (N = 11). Litter size was one, possibly caused by only one active ovarium. Sexual maturity of the two parent animals is approximately 3.5 years. The average feeding rations for the adults ranged between 10.1% BW week-1 (131 kcal kg BW-1 week-1) and 11.3% BW week-1 (172 kcal kg BW-1 week-1), with a feeding frequency of 4 times per week. The relationship between body weight (BW) and wingspan (WS) is given as BW = 3.6 × 10-5* WS2.940 (R2 = 0.9645; N = 45) (Received December 10 2007) (Accepted April 17 2009) (Online publication August 06 2009

Comparing feed intake, utilization of protein and energy for growth and body composition in S. solea fed natural and commercial diets

The present work was carried out to study the effect of polychaete Nereis virens on feed intake, utilization of protein and energy for growth and body composition in sole (S. solea). It is hypothesized that intake, efficiencies of protein utilization and growth rates obtained for sole fed ragworm are comparable to those previously reported for S. solea. The mussel M. edulis was used as a reference diet to allow comparisons of present results with those obtained previously, which until today serve as reference for optimum growth in sole. Intake, efficiencies of utilization for protein and energy for growth and growth rates obtained for sole fed ragworm are expected to be higher compared to commercial feed. A commercial feed, commonly used for turbot but also in sole culture served as a second reference diet to discuss differences between natural and commercial feeds

Energy, metabolism of young, unadapted calves

Calves reared for veal or other meat production are usually purchased before 2 weeks of age. The first weeks at the rearing unit represent a critical phase regarding their health. During this period calves are fed at a very low level. In this thesis, the energy metabolism of young, newly purchased calves, as affected by feeding level and ambient temperature, was studied. It was found that such calves are highly dependent upon body energy reserves due to restrictive feeding, their high maintenance requirements, and the low availability of nutrients from the diet. During this period, the response of these animals to temperature is not consistent with the current concept of thermoregulation. Thermal requirements are affected by the calf's posture (standing or lying). The influence of temperature on heat production of calves varies within a day. Part of this circadian fluctuation is related to the within day variation in time spent standing. The first 2 weeks after arrival the calves are not in a steady-state regarding their energy metabolism. Both the relationship between heat production and feeding level and heat production and temperature, change with time after arrival

The effect of dietary non-starch polysaccharide level and bile acid supplementation on fat digestibility and the bile acid balance in rainbow trout (Oncorhynchus mykiss)

This study investigated in rainbow trout (Oncorhynchus mykiss) if dietary bile acid supplementation is effective in restoring hampered fat digestibility related to conditions that enhance fecal bile acid loss (i.e., high dietary non-starch polysaccharide (NSP) level and high feeding level). Four diets were formulated according to a two-by-two factorial design. A Low- and High-NSP level (0 vs. 160 g kg-1 inclusion of a NSP-rich ingredient mixture) and two bile acid supplementation levels (0 vs. 2 g kg-1 inclusion of sodium taurocholate) were tested. A contrast in feeding level (i.e., feed intake) was created by subsequently feeding fish restrictively (1.1% BW d-1) for four weeks and to satiation for three weeks. The apparent digestibility coefficient (ADC) of all nutrients was affected by feeding period (i.e., restricted vs. satiation feeding), but the effect was dependent on diet composition with the ADC decline between feeding periods being larger for the High-NSP diets. The ADC of all macronutrients decreased alongside dietary NSP level, but this decrease was much more pronounced for fat compared to starch and protein, especially during satiation feeding (6.7%). This large drop in fat ADC during satiation feeding of NSP-rich diets occurred alongside enhanced fecal bile acid loss and correlated with a negative bile acid balance. The correlation between the bile acid balance and fat ADC found during satiation feeding of diets without bile acid supplementation was not present in fish fed diets with bile acid supplementation. In contrast to fat ADC, the ADC of protein and starch were independent from bile acid supplementation. In conclusion, dietary bile acid supplementation is an effective way to remediate decreased fat ADC related to enhanced fecal bile acid loss in rainbow trout, but is not effective in improving protein and starch ADC.</p

Dietary non-starch polysaccharides influenced natural food web and fish production in semi-intensive pond culture of Nile tilapia

Dietary non-starch polysaccharides (NSP) changes the nutrient digestibility and faecal characteristics in fish. This study assessed the effect of the type of dietary NSPs on fish production and the contribution of natural food to the total fish production in semi-intensively managed tilapia ponds. Twelve ponds, each divided into three equally-sized compartments, were assigned to test the effect of the type of dietary NSPs (i.e. “PecHem-Diet”, a diet with easily fermentable NSP, vs “LigCel-Diet”, a diet with slowly fermentable NSP). Fish were restrictively fed, based on the crude protein content of the feed. Three feeding levels (“no = 0”, “low = 9 g.kg-0.8.d−1” and “high= 18 g.kg-0.8.d-1”) nested in pond were analysed in a split plot design. Initial fish biomass was 3084 g.compartment−1 and the experiment lasted 56 days. With the “LigCel-Diet” biomass gain was higher (2599 vs 2192 g.compartment−1) and feed conversion ratio (FCR) was lower (1.4 vs 1.9; P 13C and δ15N from the stable isotope analysis revealed that N gain in fish originated from both feed and natural food of the pond. Natural food abundance in the pond increased over time for both diets. Chlorophyll-a was higher in the pond fed with “LigCel-Diet”. Fish gut content and calculated N gain indicated an enhanced contribution of natural food to fish growth in ponds fed with “LigCel-Diet”. In conclusion, the type of dietary NSP determines tilapia productivity in semi-intensive managed ponds by altering food web productivity.</p

Effect of ingredient particle sizes and dietary viscosity on digestion and faecal waste of striped catfish (Pangasianodon hypophthalmus)

The ingredients' particle size and dietary viscosity may alter digestion, performance and faecal waste management of fish. This study aimed to assess the effect of grinding screen sizes of feed ingredients and dietary viscosity on digestibility, faecal waste and performance of striped catfish (Pangasianodon hypophthalmus, Sauvage, 1878). The experiment had a 2 × 3 factorial-design: two feed mesh particle sizes, by grinding ingredient mixtures at two screen sizes (0.8 versus 1.0 mm); and three dietary viscosity levels, created by exchanging carboxymethylcellulose by guar gum (GG) (0, 3 and 6 g of GG/kg of diet). Six diets were assigned to 18 tanks, each connected to three faecal settling tanks. All aquaria were stocked with 20 fish (82 g per fish). After 52 experimental days, dietary viscosity negatively affected both feed digestibility and performance of striped catfish; as a result, the amount of organic matter in the culture system through faeces had increased significantly. The coarse diets significantly increased the digestibility of dry matter and carbohydrate but worsened feed conversion ratio. Increasing dietary viscosity tended to increase the viscosity and moisture content of the faeces, but significantly accelerated the faecal disintegration through the reduction of both faecal recovery and the amount of recovered faeces.</p

Isoenergetic Replacement of Fat by Starch in Diets for African Catfish (Clarias gariepinus): Effect on Water Fluxes in the Gastro Intestinal Tract

The effect of an isoenergetic replacement of dietary fat by starch, on chyme characteristics and water fluxes in the gastro intestinal tract (GIT) was assessed. Adult African catfish (Clarias gariepinus) were fed a starch (SD) or fat (FD) diet and groups of fish were dissected at 2, 5 and 8 h after the consumption of a single meal. Chyme was collected quantitatively and was analysed for osmolality and dry matter (DM) content. Postprandial water fluxes were calculated, while using yttrium oxide (Y2O3) as an inert marker to account for the absorption of DM along the GIT. The largest differences in chyme characteristics between diets were observed in the stomach and decreased towards subsequent compartments. A high initial osmotic pressure was measured in the stomach for both diets (up to 49862 mOsm kg21) and was likely the driver for the endogeneous water influx to this compartment. Large additions of water were recorded to the stomach and proximal intestine for both diets and absorption of water took place in the mid- and distal intestine. Interestingly, the dietary treatment had an impact on water balance in the stomach and proximal intestine of the fish, but not in the mid- and distal intestine. A strong complementary relationship suggested that 59% of the water fluxes in the proximal intestine could be explained by previous additions to the stomach. Therefore, a higher dietary inclusion of starch led to a shift in water additions from the proximal intestine to the stomach. However, the sum of water additions to the GIT was not different between diets and was on average 6.5260.85 ml water g21 DM. The interactions between osmoregulation and digestion, in the GIT of fed freshwater fish, deserve further attention in future research

Effect van lichtschema op energiemetabolisme en technische resultaten bij gespeende biggen

In een experiment van 2 weken zijn de effecten van het lichtschema op technische resultaten en energiemetabolisme van gespeende biggen bestudeerd

Dietary nutrient composition affects digestible energy utilisation for growth: a study on Nile tilapia (Oreochromis niloticus) and a literature comparison across fish species

The effect of the type of non-protein energy (NPE) on energy utilisation in Nile tilapia was studied, focusing on digestible energy utilisation for growth (kgDE). Furthermore, literature data on kgDE across fish species were analysed in order to evaluate the effect of dietary macronutrient composition. A total of twelve groups of fish were assigned in a 2 × 2 factorial design: two diets (‘fat’ v. ‘starch’) and two feeding levels (‘low’ v. ‘high’). In the ‘fat’-diet, 125 g fish oil and in the ‘starch’-diet 300 g maize starch were added to 875 g of an identical basal mixture. Fish were fed restrictively one of two ration levels (‘low’ or ‘high’) for estimating kgDE. Nutrient digestibility, N and energy balances were measured. For estimating kgDE, data of the present study were combined with previous data of Nile tilapia fed similar diets to satiation. The type of NPE affected kgDE (0·561 and 0·663 with the ‘starch’ and ‘fat’-diets, respectively; P <0·001). Across fish species, literature values of kgDE range from 0·31 to 0·82. Variability in kgDE was related to dietary macronutrient composition, the trophic level of the fish species and the composition of growth (fat:protein gain ratio). The across-species comparison suggested that the relationships of kgDE with trophic level and with growth composition were predominantly induced by dietary macronutrient composition. Reported kgDE values increased linearly with increasing dietary fat content and decreasing dietary carbohydrate content. In contrast, kgDE related curvilinearly to dietary crude protein content. In conclusion, energy utilisation for growth is influenced by dietary macronutrient composition