Ines Andretta

Meta-análise em pesquisas científicas: enfoque em metodologias

ABSTRACT - This text describes a basic approach of systematization with focus on meta-analysis. It ispresented the art state of the meta-analysis, recovering information of its evolution and basic methodologies for itsaccomplishment. In this text are described the historical antecedents of meta-analysis, the limits of the classicapproaches of literature review, the conceptual bases and the objectives. It is indicated a general methodology formeta-analysis procedures. The criteria for the definition of the objectives are presented. The procedures of thesystematization and management of bibliographical data base selected to meta-analytic studies are described(selection, code, data filtration). The most common analysis (graph, adjustments) are presented, the choice of thestatistical model (a qualitative explanatory factor, a qualitative or quantitative effect), the interference factors andthe post-analytic procedures (residual variations, heterogeneity among results). In conclusion, this text shows thatmeta-analysis is better than traditional methods of literature review for esteeming with more precision the treatmentseffects adjusting it’s for the experimental heterogeneity. However, the meta-analysis requires discipline in thesystematization and analysis of the research results.

Meta-analytical study of productive and nutritional interactions of mycotoxins in broilers

A meta-analysis was carried out to study the association of mycotoxins with performance, productive indices, and organ weights in broilers. Ninety-eight papers published between 1980 and 2009 were used, totaling 1,401 diets and 37,371 animals. Meta-analysis followed 3 sequential analyses: graphical, correlation, and variance-covariance. The mycotoxin presence in diets reduced (P < 0.05) feed intake by 12% and weight gain by 14% compared with control group. Ochratoxins and aflatoxins were the mycotoxins with the greatest effect on feed intake and bird growth, reducing (P < 0.05) feed ingestion by 17 and 11%, respectively, and weight gain by 20 and 11%, respectively. The mycotoxin concentration in diets and the animal age at challenge were the variables that more improved the coefficient of determination for equations to estimate mycotoxin effect on weight gain. The mycotoxin effect on growth proved to be greater in young poultry. The residual analysis revealed that 65% of the variation in weight gain was explained by feed intake. The variation in weight gain of challenged broilers in relation to nonchallenged broilers was also influenced by ingestion of nutrients such as protein and methionine. Mortality was 8.8 and 2.8 times greater (P < 0.05) in groups that received diets with deoxynivalenol and aflatoxins, respectively. Mycotoxins also increased (P < 0.05) the relative weight of liver by 15%, of kidneys by 11%, of lungs by 9%, and of gizzard by 3%. Mycotoxins influenced broiler performance, productive indices, and organ weights. However, the magnitude of the effects varied with type and concentration of mycotoxin, animal age, and nutritional factors.

Meta-analysis of the effects of endoparasites on pig performance

A meta-analysis was carried out in order to study the effects of endoparasites on the performance of growing pigs. Criteria that should be considered for the publication selection were: (1) the health challenge caused by parasites; (2) pig in growing phase; (3) presentation of the nutritional composition of the diets and (4) animal performance. Meta-analysis followed three sequential analysis: graphical, correlation and variance-covariance. The group that were infected with parasites had an average daily feed intake 5% lower than that the control group (2044 vs. 2147 g d(-1); P<0.001), their average daily weight gain was also 31% lower (665 vs. 987 g d(-1); P<0.001) and their feed conversion ratio was 17% superior than that of the control group (3.07 vs. 2.62; P<0.001). The variance decomposition demonstrated that 59% of the reduction in weight gain was explained by the reduction in their feed intake, as well as a 6% reduction being due to parasites.

Meta-analytical study of productive and nutritional interactions of mycotoxins in growing pigs.

A meta-analysis was carried out in order to study the association of mycotoxins with performance and organ weights in growing pigs. A total of 85 articles published between 1968 and 2010 were used, totaling 1012 treatments and 13 196 animals. The meta-analysis followed three sequential analyses: graphical, correlation and variance-covariance. The presence of mycotoxins in diets was seen to reduce the feed intake by 18% and the weight gain in 21% compared with the control group. Deoxynivalenol and aflatoxins were the mycotoxins with the greatest impact on the feed intake and growth of pigs, reducing by 26% and 16% in the feed intake and by 26% and 22% in the weight gain. The mycotoxin concentration in diets and the animal age at challenge were the variables that more improved the coefficient of determination in equations for estimating the effect of mycotoxins on weight gain. The mycotoxin effect on growth proved to be greater in younger animals. In addition, the residual analysis showed that the greater part of the variation in weight gain was explained by the variation in feed intake (87%). The protein and methionine levels in diets could influence the feed intake and the weight gain in challenged animals. The weight gain in challenged pigs showed a positive correlation with the methionine level in diets (0.68). The mycotoxin effect on growth was greater in males compared with the effect on females. The reduction in weight gain was of 15% in the female group and 19% in the male group. Mycotoxin presence in pig diets has interfered in the relative weight of the liver, the kidneys and the heart. Mycotoxins have an influence on performance and organ weight in pigs. However, the magnitude of the effects varies with the type and concentration of mycotoxin, sex and the animal age, as well as nutritional factors.

Meta-analysis of the performance variation in broilers experimentally challenged by Eimeria spp.

A meta-analysis was carried out to (1) study the relation of the variation in feed intake and weight gain in broilers infected with Eimeria acervulina, Eimeria maxima, Eimeria tenella, or a Pool of Eimeria species, and (2) to identify and to quantify the effects involved in the infection. A database of articles addressing the experimental infection with Coccidia in broilers was developed. These publications must present results of animal performance (weight gain, feed intake, and feed conversion ratio). The database was composed by 69 publications, totalling around 44 thousand animals. Meta-analysis followed three sequential analyses: graphical, correlation, and variance-covariance. The feed intake of the groups challenged by E. acervulina and E. tenella did not differ (P>0.05) to the control group. However, the feed intake in groups challenged by E. maxima and Pool showed an increase of 8% and 5% (P<0.05) in relation to the control group. Challenged groups presented a decrease (P<0.05) in weight gain compared with control groups. All challenged groups showed a reduction in weight gain, even when there was no reduction (P<0.05) in feed intake (adjustment through variance-covariance analysis). The feed intake variation in broilers infected with E. acervulina, E. maxima, E. tenella, or Pool showed a quadratic (P<0.05) influence over the variation in weight gain. In relation to the isolated effects, the challenges have an impact of less than 1% over the variance in feed intake and weight gain. However, the magnitude of the effects varied with Eimeria species, animal age, sex, and genetic line. In general the age effect is superior to the challenge effect, showing that age at the challenge is important to determine the impact of Eimeria infection.

Meta-analysis of the relationship of mycotoxins with biochemical and hematological parameters in broilers

A meta-analysis was carried out to study the association of mycotoxins with hematological and biochemical profiles in broilers. Ninety-eight articles published between 1980 and 2009 were used in the database, totaling 37,371 broilers. The information was selected from the Materials and Methods and Results sections in the selected articles and then tabulated in a database. Meta-analysis followed 3 sequential analyses: graphic, correlation, and variance-covariance. Mycotoxins reduced (P < 0.05) the hematocrit (-5%), hemoglobin (-15%), leukocytes (-25%), heterophils (-2%), lymphocytes (-2%), uric acid (-31%), creatine kinase (-27%), creatinine (-23%), triglycerides (-39%), albumin (-17%), globulin (-1%), total cholesterol (-14%), calcium (-5%), and inorganic phosphorus (-12%). Mycotoxins also altered (P < 0.05) the concentrations of alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase. A quadratic effect was observed on the relationship between the concentration of aflatoxin in diets and the serum concentration of alkaline phosphatase, γ-glutamyl transferase, alanine aminotransferase, and aspartate aminotransferase. The total protein concentration in blood was 18% lower (P < 0.05) in broilers challenged by aflatoxins compared with that of the unchallenged ones. The inclusion of antimycotoxin additives in diets with aflatoxins altered (P < 0.05) some variables (uric acid, creatinine, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, and γ-glutamyl transferase) in relation to the group that received diets with the mycotoxin and without the additive. The meta-analysis performed in this study allowed us to address and quantify systematically the relationship of mycotoxins with alterations in hematologic and biochemical profiles in broilers.

Alimentação de leitoas pré-púberes com dietas contendo zearalenona

The performance, the weights of some organs, and the vulvae morphology in pre-pubertal gilts fed diets containing zearalenone were evaluated during 28 days. The experimental design was completely randomized with two treatments (control diet, ZD - control diet + 2mg kg -1 of zearalenone) and six replications of each were done. No differences (P>0.05) between treatments for daily feed intake (1.24 x 1.19kg), average daily gain (0.68 x 0.71kg), feed conversion ratio (1.86 x 1.71), and live weight (30.9 x 30.4kg) were observed. Zearalenone did not change (P>0.05) the absolute and relative weights of heart (137 x 141g and 0.45 x 0.45%BW), liver (699 x 699g and 2.31 x 2.26%BW), kidneys (47 x 49g and 0.15 x 0.16%BW), and spleen (166 x 171g and 0.55 x 0.55% BW). However, zearalenone increased (P<0.05) the length (17 x 27cm) and weight (23 x 157g and 0.07 x 0.51%BW) of the reproductive tract. The final vulvae volume was 820% larger (P<0.05) in gilts fed diets containing zearalenone than those fed control diet (941 x 8658mm 3 /kgBW 0.6 ). Results suggested that zearalenone and its metabolites have an estrogenic

Relação da ractopamina com componentes nutricionais e desempenho em suínos: um estudo meta-analítico

A meta-analysis was carried to evaluate the relationship of ractopamine with nutritional variables and performance in pigs. The database included 29 articles published in national and international journals from 1990 to 2007, totaling 155 treatments and 3,786 pigs. The average inclusion of ractopamine was 15.3ppm (ranged from 0 to 30ppm) and the daily average intake of ractopamine was 24.9mg (ranging from 0 to 84mg). Inclusion of ractopamine in diets showed (P 0.05) the feed intake, but increased (P<0.05) in 12% the feed efficiency, in 10% the weight gain and in 3.7% the final body weight. The concentrations of protein, lysine and energy in diets affected the animal response feeding with ractopamine. Increasing a unit in dietary lysine concentration resulted in increase of 341g in weight gain (ADG=0.687+0.341LIS, R²=0.71) and 1.3% in feeding efficiency (EF=2.14+1.34LIS; R²=0.62). Ractopamine improves pig performance, however, the interaction between additive and nutritional components must be considered in diets formulation.

A meta-analysis of the feed intake and growth performance of broiler chickens challenged by bacteria

The aim of this meta-analysis was to determine the effect of a bacterial immune challenge (Clostridium spp., Escherichia coli, and Salmonella spp.) on the ADFI, ADG, and nutrient partitioning (maintenance requirements and feed efficiency) of broiler chickens. The database used for the meta-analysis included 65 articles that were published between 1997 and 2012 concerning a total of 86,300 broilers and containing information on the feed intake, protein intake, methionine intake, and weight gain of broilers that were challenged with Clostridium spp., E. coli, or Salmonella spp. and were fed or not fed feed additives. The results of the ADFI and the ADG of the challenged broilers were transformed into values relative to those obtained in control broilers (ADG and ADFI). The meta-analysis involved 3 sequential analyses: graphical, correlation, and variance-covariance analysis. The results obtained for the birds that were challenged with Clostridium spp., E. coli, or Salmonella spp. indicated that the ADFI was reduced by 16, 7, and 9%, respectively, and the ADG was reduced by 40, 10, and 29%, respectively. When the results for the challenged birds that were treated or nontreated were compared, ADFI reductions of 26.0 and 26.5% and ADG reductions of 2.9 and 21.6% were observed, respectively. Regression analyses of the ADG as a function of the protein or methionine intake of the challenged birds suggested that nutrients were diverted to the immune system. The relationship between the ADG and the ADFI was quadratic in the challenged and nontreated or treated broilers, as well as for each disease. The intercept of the regression-based curves for the data from all of the challenges were different from zero and negative (-2.20, -0.70, and -3.37, respectively), indicating that all of the challenges increased the maintenance requirements. In general, this meta-analysis allowed for the quantification of the effects of bacteriological challenges on the maintenance and feed efficiency of broiler chickens, and the knowledge that was generated in this study is applicable to broiler nutrition and for modeling their nutritional requirements.

Criação intensiva de suínos em confinamento ou ao ar livre: estudo meta-analítico do desempenho zootécnico nas fases de crescimento e terminação e avaliação de carcaça e carne no Longissimus dorsi

A meta-analysis was carried out to study performance and characteristics of carcass and meat in pigs in function of housing system during the growing/finishing period. Indexed publications with results of experiments comparing performance and post-slaughter variables of pigs housed in outdoor or conventional intensive systems were selected. In total, 2.985 animals and 701 averages were considered in the data analysis. Meta-analysis followed two sequential analyses: graphic and variance. The outdoor productive system increased in 9% (P 0.05) by the housing system. It is concluded that the housing system influences the pig performance, but does not interfere in characteristics of carcass and meat.