A comparison of two methods for determining titanium dioxide marker content in broiler digestibility studies

The use of inert markers in broiler diets eliminates the need to quantitatively evaluate feed intake and excreta output to determine diet digestibility, and enables nutrient uptake at specific points along the gastrointestinal tract to be examined. Titanium dioxide (TiO2) is commonly used for this purpose and measured using a UV spectrophotometric assay. Two experiments were conducted to observe whether an inductively coupled plasma optical emission spectrophotometer (ICP-OES) assay is able to replace the UV-spectroscopy assay for rapid analysis of TiO2 in broiler feed and ileal digesta samples. In the first experiment, TiO2 was added at 5g/kg to 19 broiler diets. Ross 308, male broilers (n=452) fed these diets were involved in a series of digestion studies to determine ileal digesta recovery of TiO2. In the second experiment, defined amounts of TiO2 were added to ileal digesta samples from Ross 308, male broilers (n=176) and TiO2 recoveries were determined

Use of Zn concentration in the gastrointestinal tract as a measure of phytate susceptibility to the effect of phytase supplementation in broilers

Zinc (Zn) is the most vulnerable cation to complexation with phytate. An experiment was conducted to evaluate the potential of measurements of Zn concentration in the gastrointestinal tract as a marker to assess the anti-nutritional impact of phytate and susceptibility of phytate to phytase in broilers. Ross 308 broilers (n = 180) were fed one of 5 experimental diets with differing phytase activity levels, analyzed at 605, 1150, 1804, 3954 and 5925 U/kg. Broiler performance and Zn concentration, pH and amount of phytate hydrolyzed in the gizzard, duodenum and ileum were analyzed at d21 post hatch. Phytate susceptibility to phytase degradation was determined in vivo and in vitro by measuring total phytate-P hydrolyzed in the tract or in conditions that mimicked the tract, respectively. Phytase activity level had a significant (P < 0.05) impact on Zn concentration and phytate hydrolyzed in the gizzard and ileum, but not in the duodenum. Strong relationships were observed between the amount of phytate hydrolyzed and Zn concentration in the gizzard in birds fed the diets with 1804 U/kg or higher levels of phytase. Phytate and phytase effects could therefore potentially be evaluated by measuring Zn concentration in the gizzard. Susceptible phytate levels measured in vivo and in vitro were almost identical in the diet with phytase activity of 5925 U/kg, but in the diets with lower phytase activity levels the in vitro assay overestimated the amount of P released. There were strong relationships between in vivo susceptible phytate level and pH and amount of phytate hydrolyzed in the gizzard, duodenum and ileum and Zn concentration in the gizzard and ileum. This illustrates that phytate susceptibility directly effects mineral availability in the gastrointestinal tract. Measurements of Zn concentration in the gastrointestinal tract, particularly in the gizzard, can potentially be used as a marker to assess the anti-nutritional impact of phytate and susceptibility of phytate to phytase in broilers

Quantification and alleviation of the antinutritional effects of phytate on poultry

The phosphorus (P) requirements of meat-type poultry cannot be met by plant-based diets because approximately two thirds of total phosphorus in cereals and leguminous feed materials is in the unavailable form of phytate (inositol hexaphosphate or phytic acid). Phosphorus supplements are expensive and over supplementation can increase excretion of P, with negative implications on the environment. For some time, research has focussed on the development of exogenous phytase enzymes capable of releasing phytate phosphorus for absorption, thus reducing the environmental impact of poultry production and requirements for costly dietary inorganic P supplementation. The absolute adoption of this strategy has, however, been stalled by apparent variability in rate of release of phytate by phytase enzyme. The aim of this project was to examine the availability and reactivity of phytate in diets and raw materials fed to broilers in a range of physiological environments, and to develop strategies for combating their effects. A series of in vitro studies and bird trials were conducted to investigate phytate reactivity by observing the relationship between pH, protein phytate interactions and phytate susceptibility to the effects of phytase. A bird trial was undertaken comparing the current commercial level of 500 FTU/kg phytase and a superdose of 5000 FTU/kg phytase in soyabean meal and rapeseed meal based broiler diets. Feeding phytase doses above the commercial recommendation resulted in increased bird performance through phytate destruction, leading to heightened alleviation of the anti-nutritional effects of phytate. This suggests that superdosing broiler diets can improve profitability by both increasing availability of phosphorus and removing restrictions of using cheaper feed ingredients which are viewed as undesirable due to their high phytate content. There is a common misconception that poultry lack any endogenous phytase, but a study sequentially sampling broilers from age d4 to d14 illustrated that phytase activity from intestinal mucosa and bacteria and diet is quantifiable in regulating phytate-P digestion. Endogenous phytase contributes significantly towards degradation of phytate at bird age d4. By d14, ileal phytase activity levels were approximately 45 U/kg and the amount of total dietary phytate hydrolysed ranged from 21% to 36%. Measurements of total phytate-P content of diets may be deceptive as they do not indicate substrate availability for phytase; measurements of phytate susceptible to the effects of phytase may be a more accurate measure of phosphorus availability to the bird. To verify this hypothesis in practice, a bird study was designed to compare diets formulated to contain high or low susceptible phytate. This study showed that at age d28, birds fed diets with high susceptible phytate content had significantly better cumulative BWG (p=0.015) and FCR (p=0.003) than birds fed diets with low susceptible phytate content. Furthermore, in vitro screening of raw materials revealed that phytate susceptibility varies considerably between ingredients and batches of ingredients, and total phytate content bears no relation to susceptible phytate content of an ingredient. Therefore, for optimum phytase efficacy, it may be advantageous to formulate diets and develop phytase matrix values based on the susceptible phytate content of the individual batch of ingredients being fed. Both total and susceptible phytate content can be measured using simple colorimetric assays. Examination of in vitro digestion models and subsequent correlation to in vivo studies indicate that exposing samples to conditions that mimic the gastrointestinal environment is the most accurate way to predict phytate degradation and mineral availability in diets prior to feeding. The relationship between phytate reactivity and pH was investigated throughout this project. It was found that gastric pH is closer to the optimum for pepsin activity and phytate-complex degradation when in the presence of phytase. This is because phytate reduces protein digestibility, resulting in heightened presence of intact proteins in the tract, which instigates an increase in secretion of HCl and pepsin. More bicarbonate ions are released in response to this increased acidity, causing an increase in intestinal pH and resulting reduction in solubility of phytate-protein complexes. To conclude, dietary phytate that is susceptible to phytase effects as opposed to total phytate content should potentially be considered when determining phytase matrix values. For optimum response to phytase, it may be beneficial to formulate diets based on the susceptible phytate content of the individual batch of ingredients being fed. Some raw materials have high total phytate content but also high susceptible phytate content, meaning they have the potential to be used as replacements for more expensive feed ingredients if in the presence of phytase. This is particularly the case in diets supplemented with high doses of phytase (>500 FTU/kg), because high phytase doses alleviate the extra-phosphoric anti-nutritional effects of phytate as well as increase mineral availability

Contribution of intestinal- and cereal-derived phytase activity on phytate degradation in young broilers

There is little consensus as to the capability of poultry to utilize dietary phytate without supplemental phytase. Therefore, an experiment was conducted to examine the extent to which endogenous phytase of intestinal and cereal origin contributes to phytate degradation in birds aged 0 to 14 d posthatch. Ross 308 broilers (n = 720) were fed one of 4 experimental diets with differing dietary ingredient combinations and approximate total phytate levels of 10 g/kg, dietary phytase activity analyzed at 460 U/kg, dietary calcium (Ca) levels of 11 g/kg, and nonphytate-phosphorus (P) levels of 4 g/kg. Broiler performance, gizzard, duodenum, jejunum and ileum pH, Ca and P digestibility and solubility, amount of dietary phytate hydrolyzed in the gizzard, jejunum, and ileal digesta phytase activity were analyzed at d 4, 6, 8, 10, 12, and 14 posthatch. Intestinal endogenous phytase activity increased significantly (P < 0.001) between d 4 and 6, resulting in increased phytate hydrolysis in the gizzard (P = 0.003), jejunum (P < 0.001), and ileum (P < 0.001). Phytase activity and phytate hydrolysis continued to increase with age, with a greater phytase activity and associated increase in phytate hydrolysis and mineral utilization between d 10 and 12. Gizzard and jejunum Ca and P solubility and ileal Ca and P digestibility increased significantly (P < 0.001), and gastrointestinal pH decreased significantly (P < 0.001) between d 4 and 6. By d 14, phytase activity recovered in the ileum was approximately 45 U/kg. There were strong correlations between phytase activity measured in the ileum and phytate hydrolyzed in the gizzard (r = 0.905, P < 0.001), jejunum (r = 0.901, P = 0.023), and ileum (r = 0.938, P = 0.042). This study shows intestinal- and dietary-derived endogenous phytase activity is responsible for phytate-P hydrolysis in broilers

In vitro versus in situ evaluation of the effect of phytase supplementation on calcium and phosphorus solubility in soya bean and rapeseed meal broiler diets

1. In vitro assays provide a sensitive and economic tool to evaluate dietary effects, but have limitations. In this study, the effect of phytase supplementation on solubility, and presumed availability, of calcium (Ca) and phosphorus (P) in soybean meal (SBM) and rapeseed meal (RSM) based diets was evaluated both in situ and by a 2-step in vitro digestion assay that simulated the gastric and small intestine (SI) phases of digestion

Use of mixed methods designs in substance research: a methodological necessity in Nigeria

The utility of mixed methods (qualitative and quantitative) is becoming increasingly accepted in health sciences, but substance studies are yet to substantially benefit from such utilities. While there is a growing number of mixed methods alcohol articles concerning developed countries, developing nations are yet to embrace this method. In the Nigerian context, the importance of mixed methods research is yet to be acknowledged. This article therefore, draws on alcohol studies to argue that mixed methods designs will better equip scholars to understand, explore, describe and explain why alcohol consumption and its related problems are increasing in Nigeria. It argues that as motives for consuming alcohol in contemporary Nigeria are multiple, complex and evolving, mixed method approaches that provide multiple pathways for proffering solutions to problems should be embraced

AIDS-defining illnesses among patients with HIV in Singapore, 1985 to 2001: results from the Singapore HIV Observational Cohort Study (SHOCS)

BACKGROUND: The objective was to describe the causes of initial and overall AIDS-defining disease episodes among HIV patients in Singapore. METHODS: A retrospective observational cohort study was performed of all adult patients seen at the national HIV referral center between 1985 and 2001. Data were extracted from the patients' records by ten trained healthcare workers. AIDS-defining conditions were established using predefined criteria. RESULTS: Among 1504 patients, 834 had experienced one or more AIDS-defining diseases. The most frequent causes of the initial AIDS-defining episode were Pneumocystis carinii pneumonia (35.7%), Mycobacterium tuberculosis (22.7%) and herpes simplex (7.4%). In total 1742 AIDS-defining episodes occurred. The most frequent causes were Pneumocystis carinii pneumonia (25.1%), Mycobacterium tuberculosis (16.2%) and cytomegalovirus retinitis (9.5%). CONCLUSIONS: The most frequent causes of AIDS-defining illnesses in Singapore are similar to those reported in the West, prior to the introduction of anti-retroviral therapy. Opportunistic infections remain the most frequent AIDS-defining illnesses

Mental health care for irregular migrants in Europe: Barriers and how they are overcome

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New Strategies for Research in Clinical Practice: A focus on self–harm.

This article suggests new ways of approaching clinical-based research in an era of evidence-based practice. Using the example of self-harm, we identify three distinct problems with current dominant approaches to research in this area. These include insufficient clarity about target issues, an overreliance on predetermined outcomes which prioritise behavioural measures (such as self-harm cessation) and an undue focus on treatment techniques. We argue that clinical research requires flexible, user-centred and practice-based methods, informed by a focus on principles instead of techniques. Therefore, we outline key practice-based principles that we argue need to be embedded within clinical research strategies. We then demonstrate how traditional behavioural approaches to research can be enriched with more qualitative cognitive and emotionally based data. We conclude that such strategies provide thickened, meaningful and context-specific research which is more relevant for service commissioners, clinicians and service users