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Prague, Czech Republic

Consumer preference for poultry meat from free-range birds is not justified by scientific evidence. Inconsistency in results among studies on the effects of access to pasture on performance, carcass composition, and meat quality has led to a meta-analysis to quantify effects. After identification of studies where response variables were directly compared between birds with and without access to pasture, standardized effect sizes were used to calculate differences. The effect size for growth combined according to a fixed effect model did not present heterogeneity (P = 0.116). However, with feed intake and feed efficiency, variability among studies (heterogeneity with P-values of below 0.10) was influenced by more than sampling error. Carcass yield was the only carcass component that showed heterogeneity (P = 0.008), whereas numerous response variables related to meat quality were not homogenous. The use of subgroup analysis and meta-regression to evaluate the sources of heterogeneity was limited by ill-defined explanatory variables and few values available within response variables. Consequently, between-study variability was accounted for by use of random effects models to combine effect sizes. According to these, few response variables were influenced by pasture access. Fat concentrations in breast (mean effect size = -0.500; 95% CI = -0.825 to -0.175; 11 studies; 14 comparisons), thigh (mean effect size = -0.908; 95% CI = -1.710 to -0.105; 4 studies; 5 comparisons) and drum (mean effect size = -1.223; 95% CI = -2.210 to -0.237; 3 studies; 3 comparisons) muscles were decreased in free-range birds. Access to pasture increased (P < 0.05) or tended to increase (P < 0.10) protein concentrations in the respective commercial cuts. It is concluded that factors other than enhanced meat quality could be responsible for consumer preference for meat from free-range poultry. © 2014 Poultry Science Association Inc. Source

Inconsistent results of the effects of dietary betaine supplementation on important economic carcass characteristics of finishing pigs have been reported. This has motivated a quantitative meta-analysis that accounted for variability among experiments. Through an extensive literature search data have been identified to evaluate the effects of dietary betaine supplementation on average daily feed intake (ADFI; 11 experiments, 18 comparisons), average daily gain (ADG; 13 experiments, 21 comparisons), backfat thickness (BFT; 10 experiments, 13 comparisons), dressing proportion (DP; 7 experiments, 10 comparisons), feed conversion ratio (FCR; 12 experiments, 18 comparisons), longissimus dorsi muscle area (LMA; 9 experiments, 13 comparisons), proportion carcass lean (PCL; 7 experiments, 10 comparisons) and tenth rib fat thickness (TRFT; 7 experiments, 10 comparisons). Statistical analyses included: (1) fixed and random effects models to calculate summary statistics for standardised effect sizes (Hedges's g) of the difference between control and betaine-fed pigs; (2) meta-regression to evaluate the sources of heterogeneity of responses; (3) the assessment of possible publication bias. Dietary betaine supplementation had no influence (P > 0.05) on ADG. However, feed per unit of weight gain significantly decreased (mean effect size of -0.361) in betaine-fed pigs. Whereas dressing proportion was increased (mean effect size of 0.358; P < 0.05) by betaine supplementation, BFT was decreased with a mean effect size of -0.286. The occurrence (P < 0.10) of heterogeneity showed that the effects of betaine varied from experiment to experiment for ADFI, PCL, LMA and TRFT. With ADG and TRFT some of this variability could be explained by a negative relationship (P < 0.10) between effect size and level of betaine supplementation. Existing tests could not detect evidence of any possible publication bias. This study presented conclusive results that betaine supplementation of diets for finishing pigs decreased carcass characteristics typically used as indicators of carcass fatness. © 2011 Elsevier B.V. Source

After an extensive literature search, meta-analytic techniques (fixed effect, random effects and hierarchical Bayesian models) were applied to numerically describe sizes and precision of effects caused by castration of intact rams on several performance, carcass and meat quality response variables. According to random effects models, rams presented greater (P<. 0.05) average daily gain, loin muscle area (leaner carcasses) and instrumental meat tenderness (more tough), with lower feed conversion ratios, dressing percentages and backfat thickness (less carcass fat) compared to castrates. These results could be applied in further strategies on the use of castration in male sheep. © 2014 Elsevier Ltd. Source

Pharmacological dietary zinc (Zn) concentrations of 1,000 to 3,000 mg/kg diet from Zn oxide have been found to increase growth in post-weaning pigs. However, results were inconsistent among studies. A frequentist meta-analysis, in which effects were numerically described with standardized effect sizes (Hedges's g), was conducted in order to identify and quantify the responses in average daily gain (ADG), average daily feed intake (ADFI), and gain to feed ratio (G/F) in post-weaning pigs upon dietary Zn supplementation from Zn oxide. The inability of independent continuous variables to explain significant heterogeneity obtained with fixed effect models necessitated the use of random effects models to calculate summary statistics. Dietary Zn supplementation increased (P < 0.05) ADG (mean effect size = 1.086, 95 % confidence intervals = 0.905-1.266, 26 studies, 72 comparisons), ADFI (mean effect size = 0.794, 95 % confidence intervals = 0.616-0.971, 25 studies, 71 comparisons), and G/F (mean effect size = 0.566, 95 % confidence intervals = 0.422-0.710, 24 studies, 70 comparisons). Zinc oxide provided a feasible alternative to in-feed antibiotics to improve growth in post-weaning pigs, and its reduction in diets due to potential environmental pollution will have to be negated by alternative feed additives and management strategies in order to prevent economic losses. © 2013 Springer Science+Business Media New York. Source

Nuclear localization of signal transducer and activator of transcription (Stat) 5 marks good prognosis in estrogen receptor/progesterone receptor-positive breast tumors. This positive characteristic is counteracted by studies in laboratory animals demonstrating that deregulated Stat5 activity may convert proper mammary development into a latent oncogenic process. Tumorigenesis is initiated during the parity cycles, most probably during pregnancy, when the activated Stat5 antagonizes or manipulates parity's protective mechanisms. For example, it can alter the differentiation/proliferation balance, induce growth hormone signaling, cause specific alteration in chromatin structure, inhibit tumor-suppressor activity and induce DNA damage that counteracts the enhanced DNA-damage response exerted by parity. Palpable tumors develop after a latent period from individual cells. This happens in the estropausal period in transgenic mice maintaining deregulated Stat5 activity in the mammary gland, or during involution, months after transplantation of transfected cells with constitutively active Stat5. Candidate vulnerable cells are those which maintain high nuclear Stat5 activity. Due to the hazardous outcome of deregulated Stat5 activity in these cells, such as induced DNA damage or high cyclin D1 activity, the gland is prone to transformation. The developing tumors are mostly adenocarcinomas or their subtypes. They are estrogen receptor-positive and maintain a specific Stat5 gene signature that allows tracking their inducer. From a clinical point of view, deregulated Stat5 activity represents a genuine risk factor for breast cancer. Monitoring Stat5 activity during vulnerable periods and developing specific tools for its suppression in breast epithelial cells could potentially limit new incidence of the disease. © The Author 2012. Published by Oxford University Press. All rights reserved. Source

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