Tracing the fate of N-15-enriched feed in an intensive shrimp system

The fate of N-15-nitrogen-enriched formulated feed fed to shrimp was traced through the food web in shallow, outdoor tank systems (1000 1) stocked with shrimp. Triplicate tanks containing shrimp water with and without sediment were used to identify the role of the natural biota in the water column and sediment in processing dietary nitrogen (N). A preliminary experiment demonstrated that N-15-nitrogen-enriched feed products could be detected in the food web. Based on this, a 15-day experiment was conducted. The ammonium (NH4+) pool in the water column became rapidly enriched (within one day) with N-15-nitrogen after shrimp were fed N-15-enriched feed. By day 15, 6% of the added N-15-nitrogen was in this fraction in the 'sediment' tanks compared with 0.4% in the 'no sediment' tanks. The particulate fraction in the water column, principally autotrophic nanoflagellates, accounted for 4-5% of the N-15-nitrogen fed to shrimp after one day. This increased to 16% in the 'no sediment' treatment, and decreased to 2% in the 'sediment' treatment by day 15. It appears that dietary N was more accessible to the phytoplankton community in the absence of sediment. The difference is possibly because a proportion of the dietary N was buried in the sediment in the 'sediment' treatment, making it unavailable to the phytoplankton. Alternatively, the dietary N was retained in the NH4+ pool in the water column since phytoplankton growth, and hence, N utilization was lower in the 'sediment' treatment. The lower growth of phytoplankton in the 'sediment' treatment appeared to be related to higher turbidity, and hence, lower light availability for growth. The percentage N-15-nitrogen detected in the sediment was only 6% despite the high capacity for sedimentation of the large biomass of plankton detritus and shrimp waste. This suggests rapid remineralization of organic waste by the microbial community in the sediment resulting in diffusion of inorganic N sources into the water column. It is likely that most of the dietary N will ultimately be removed from the tank system by water discharges. Our study showed that N-15-nitrogen derived from aquaculture feed can be processed by the microbial community in outdoor aquaculture systems and provides a method for determining the effect of dietary N on ecosystems. However, a significant amount of the dietary N was not retained by the natural biota and is likely to be present in the soluble organic fraction. (C) 2002 Elsevier Science B.V. All rights reserved.

What We Don't Know Could Hurt Us: A Single Center Study of Batch-to-Batch Variability of Dietary Fluids and Matched Videofluoroscopy Fluids

This study examines batch-to-batch variability in the production of dietary fluids and videofluoroscopy fluids of a single hospital. The material properties, such as viscosity, yield stress, and density, show significant variations between batches. Also waterbased products (i.e., cordial) provide (a) the most stability from week to week for both dietary and videofluoroscopy fluids and (b) the best dietary and videofluoroscopy fluid matches. The study also highlights the need for further research into how base substances, such as water, juice, and dairy products, react with different thickeners and with barium.

Manipulation of colonic bacteria and volatile fatty acid production by dietary high amylose maize (amylomaize) starch granules

Aims : To study the effects of amylomaize starch and modified (carboxymethylated and acetylated) amylomaize starches on the composition of colonic bacteria and the production of volatile fatty acids, in mice. Methods and Results : Balb/c mice were fed with experimental diets containing various amount of amylomaize and modified amylomaize starches. Colonic bacterial populations and short-chain fatty acids were monitored. Results showed that the increases in indigenous bifidobacteria were detected in mice fed all starches tested; however, the highest numbers were observed in the group fed with 40% unmodified amylomaize starch. The starch type influenced the populations of indigenous Lactobacillus , Bacteroides and coliforms. High Lactobacillus numbers were achieved in the colon of mice fed with high concentration of amylomaize starch. Acetylated amylomaize starch significantly reduced the population of coliforms. In addition, orally dosed amylomaize utilizing bifidobacteria reached their highest levels when fed together with amylomaize or carboxymethylated amylomaize starch and in both cases butyrate levels were markedly increased. Conclusions: These results indicate that different amylomaize starches could generate desirable variation in gut microflora and that particular starches may be used to selectively modify gut function. Significance and Impact of Study: Amylomaize starch appeared to enhance the desirable composition of colonic bacteria in mice, and suggested it possessed the potential prebiotic properties.MTherefore, resistant starch and its chemical derivatives may exert beneficial impacts to the human colon.

The effects of level of dietary protein on the milk production and rumen physiology of dairy cows fed a diet based on a tropical grass hay

zFour rumen-fistulated, multiparous Holstein-Friesian cows in early lactation were offered mixed diets based on rhodes grass hay (Chloris gayana) cv. Callide containing 13, 14, 15 or 16% crude protein (CP) on a dry matter basis, in a 4 x 4 latin square design. The estimated undegradable protein concentration in these diets was similar with rumen degradable protein concentration varying. Cows fed a diet containing 13% CP had lower (P = 0.07) milk yields than cows in other treatments (20.4 vs 21.9, 22.0 and 22.2 L/d for 13, 14, 15 and 16% CP, respectively). A positive linear relationship was found (P = 0.06) between organic matter intake and dietary CP%. There were negative linear relationships between dietary CP% and digestibilities of dry matter (P = 0.09), organic matter (P = 0.06) and neutral detergent fibre (P = 0.02). Feeding a diet containing 13% CP resulted in significantly lower (P = 0.001) molar proportions (%) of rumen valerate in comparison with other treatments. The molar proportions of isovalerate differed (P = 0.001) between treatments (0.66, 0.78, 0.89 and 1.04%) for 13, 14, 15 and 16% CP, respectively). Dietary protein level had no effect on rates of passage, in situ digestion of rhodes grass hay or ratios of allantoin: creatinine in urine. These data showed that increasing the dietary CP concentration of lactating cows fed diets based on rhodes grass hay increased intakes and not significantly improved at dietary CP concentrations above 14% DM.

Dietary supplementation with vitamin E modulates avian intestinal immunity

The effect of dietary vitamin E on immunoglobulin A (IgA) antibody production, which acts as the first line of defence at the intestinal mucosa, has not been evaluated in chickens. In the present study the impact of the inclusion of supplementary levels of vitamin E to the diet, on total and antigen-specific IgA antibody titres, T-cell subsets and Ia+ cells, was assessed. From hatching, chickens received a maize-based diet which was supplemented with either 25, 250, 2500 or 5000 mg dl-alpha-tocopherol acetate/kg. Primary immunisation with tetanus toxoid (T. toxoid) emulsified in a vegetable oil-in-water adjuvant was administered by the intraperitoneal route at 21 d of age. At 35 d of age all birds received an oral booster vaccination of T. toxoid. Significantly higher total IgA antibody titres were present in the day 42 intestinal scrapings of birds receiving the 5000 mg/kg vitamin E-supplemented diet (VESD) (P=0.05) and a notable increase was observed in birds receiving the 250 mg/kg VESD (P=0.06). At days 21 and 42 total serum IgA antibody titres of birds receiving the 250 mg/kg VESD was significantly higher (P

Effects of dietary level of protein, lysine and methionine and strain of bird on production and egg yolk cholesterol

The effects of dietary level of protein (151, 181 g/kg), lysine (nil, 10g L-lysine hydrochloride/kg) and methionine (nil, 5g DL-methionine/kg) on the production performance and egg yolk cholesterol of two strains of birds were studied for 12 weeks. Birds fed on the high protein diet had higher body weight gain, feed conversion ratio (FCR), rate of lay, egg weight and mass and yolk weight and mass. A high lysine diet decreased feed intake and improved FCR. High dietary level of methionine increased egg yolk cholesterol. There were differences between strains of laying bird in feed intake, rate of lay, egg and yolk weights and egg cholesterol content. It is concluded that strain of bird and dietary level of protein and lysine influenced the production performance of birds. Whilst, egg yolk cholesterol was not reduced by any of the factors studied.

Biaxial failure model for fiber reinforced concrete

Steel fiber reinforced concrete (SFRC) is widely applied in the construction industry. Numerical elastoplastic analysis of the macroscopic behavior is complex. This typically involves a piecewise linear failure curve including corner singularities. This paper presents a single smooth biaxial failure curve for SFRC based on a semianalytical approximation. Convexity of the proposed model is guaranteed so that numerical problems are avoided. The model has sufficient flexibility to closely match experimental results. The failure curve is also suitable for modeling plain concrete under biaxial loading. Since this model is capable of simulating the failure states in all stress regimes with a single envelope, the elastoplastic formulation is very concise and simple. The finite element implementation is developed to demonstrate the conciseness and the effectiveness of the model. The computed results display good agreement with published experimental data.

Dietary influences on survival after ovarian cancer

We evaluated the effects of various food groups and micronutrients in the diet on survival among women who originally participated in a population-based case-control study of ovarian cancer conducted across 3 Australian states between 1990 and 1993. This analysis included 609 women with invasive epithelial ovarian cancer, primarily because there was negligible mortality in women with borderline tumors. The women's usual diet was assessed using a validated food frequency questionnaire. Deaths in the cohort were identified using state-based cancer registries and the Australian National Death Index (NDI). Crude 5-year survival probabilities were estimated using the Kaplan-Meier technique, and adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were obtained from Cox regression models. After adjusting for important confounding factors, a survival advantage was observed for those who reported higher intake of vegetables in general (HR = 0.75, 95% CI = 0.57-0.99, p-value trend 0.01 for the highest third, compared to the lowest third), and cruciferous vegetables in particular (HR = 0.75, 95% CI = 0.57-0.98, p-value trend 0.03), and among women in the upper third of intake of vitamin E (HR = 0.76, 95% CI = 0.58-1.01, p-value trend 0.04). Inverse associations were also seen with protein (p-value trend 0.09), red meat (p-value trend 0.06) and white meat (p-value trend 0.07), and modest positive trends (maximum 30% excess) with lactose (p-value trend 0.04), calcium and dairy products. Although much remains to be learned about the influence of nutritional factors after a diagnosis of ovarian cancer, our study suggests the possibility that a diet high in vegetable intake may help improve survival. (C) 2003 Wiley-Liss, Inc.