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Meta-analysis of the effects of intensive rearing environments on the performance and welfare of broiler chickens.

ABSTRACT: To better understand how relevant intensive systems' characteristics simultaneously affect the performance and welfare of broiler chickens, a meta-analysis of recent literature was carried out. The study determined the effects of gender, genetics, experimental initial age (EIA, d), stocking density (SD; kg/m2), group size (GS; n), bedding material (yes/no), duration of photoperiod (DP; h), divided scotoperiod (yes/no), feeding phases (1/2/3/>3), environmental control (EC; yes/no), environmental enrichment (yes/no), use of vaccines and other medications (yes/no), experimental duration (d), and relevant 2-way interactions on average daily gain (g/d), average daily feed intake (g/d), FCR (g: g), mortality (%), behavior (%), and gait score (mean value). Predictive equations for response variables were calculated using multiple regression models including a random experiment effect. Among other results, EIA × SD interaction indicated that relatively high SD may improve FCR at older ages, but parallel increased mortality would pose concerns about the actual productive benefits and welfare. Combining large GS and relatively low SD seem to improve performance and decrease flock disturbance. They would also increase leg problems, and so their actual benefits on welfare remain unclear. A gradual increase in FCR seems to occur with longer DP at older EIA (EIA × DP interaction), highlighting the importance of adapting light programs to flock age to optimize performance. The SD × DP and GS × DP interactions predicted increased FCR for longer DP at low SD or large GS, that is, with more effective space available. Longer DP combined with low SD or large GS would overall promote enhanced leg conditions, and therefore welfare. Predictions would not support scotoperiod division from both performance and welfare perspectives. The SD × EC interaction indicated that EC would benefit chicken performance at low SD, although EC would seem to increase leg problems. Our study highlights the complex, interactive nature of production systems' characteristics on broiler chicken performance and welfare.

SUBMITTER: Averos X

PROVIDER: S-EPMC6162358 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Meta-analysis of the effects of intensive rearing environments on the performance and welfare of broiler chickens.

Averós X X Estevez I I

Poultry science 20181101 11

To better understand how relevant intensive systems' characteristics simultaneously affect the performance and welfare of broiler chickens, a meta-analysis of recent literature was carried out. The study determined the effects of gender, genetics, experimental initial age (EIA, d), stocking density (SD; kg/m2), group size (GS; n), bedding material (yes/no), duration of photoperiod (DP; h), divided scotoperiod (yes/no), feeding phases (1/2/3/>3), environmental control (EC; yes/no), environmental ...[more]

PMID: 29924356

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Project description:Increasing environmental complexity, e.g., by providing environmental enrichment, has been suggested as a way to increase activity levels and improve leg health in broilers. The aim of this study was to investigate the effects of different types of environmental complexity on leg health and measures of welfare of fast-growing broilers housed according to conventional European legislation. A total of 58 pens with approximately 500 broilers each (Ross 308), corresponding to a stocking density of 40 kg/m2, were used. A total of 8 treatment groups, of which 5 were enrichment treatments (roughage, vertical panels, straw bales, and elevated platforms at 5 and 30 cm) and 3 were standard resources manipulations [increased distances between feed and water (7 m and 3.5 m), stocking density reduced to 34 kg/m2, and 1 control group (1.5 m distance between feed and water and no enrichment objects)] were randomly assigned to each pen. At 35 D of age, 60 birds from each pen were assessed for gait, footpad dermatitis, hock burns, plumage cleanliness, presence of scratches, and leg deformities. Birds housed with 30 cm elevated platforms had worse gait compared to those housed with straw bales and at the lower stocking density of 34 kg/m2 (P = 0.004 and P = 0.001). Broilers from the control group also had worse gait compared to those housed at 34 kg/m2 stocking density. In addition, birds housed with access to a 30 cm elevated platform had healthier footpads compared to birds housed with access to straw bales (P = 0.0001) and with increased distance between feed and water (P = 0.011). Furthermore, birds housed with straw bales had worse footpad condition compared to birds with access to a 5 cm elevated platform (P = 0.002). There were no observed treatment effects on scratches, plumage cleanliness, leg deformities and body weight (P > 0.05). Based on the welfare indicators used in the present study, decreased stocking density has the potential of improving animal welfare, whereas the effects of elevated platforms need to be further studied before a final conclusion can be drawn, as footpad health was positively affected, but walking ability was impaired.

Project description:A 'meta-analysis' was performed to determine effects of post-hatch food and water deprivation (PHFWD) on chicken development, performance and welfare (including health). Two types of meta-analysis were performed on peer-reviewed scientific publications: a quantitative 'meta-analysis' (MA) and a qualitative analysis (QA). Previously reported effects of PHFWD were quantified in the MA, for variables related to performance, mortality and relative yolk sac weight. The QA counted the number of studies reporting (non-)significant effects when five or more records were available in the data set (i.e. relative heart, liver and pancreas weight; plasma T3, T4 and glucose concentrations; relative duodenum, jejunum and ileum weight; duodenum, jejunum and ileum length; and villus height and crypt depth in duodenum, jejunum and ileum). MA results indicated that 24 hours of PHFWD (i.e. ≥12-36 hours) or more resulted in significantly lower body weights compared to early-fed chickens up to six weeks of age. Body weights and food intake were more reduced as durations of PHFWD (24, 48, 72, ≥84 hours) increased. Feed conversion rate increased in chickens up to 21 and 42 days of age after ≥84 hours PHFWD in comparison with chickens fed earlier. Total mortality at day 42 was higher in chickens after 48 hours PHFWD compared to early fed chickens or chickens after 24 hours PHFWD. First week mortality was higher in chickens after ≥84 hours PHFWD than in early fed chickens. The MA for relative yolk sac weight was inconclusive for PHFWD. The QA for plasma T3, T4 and glucose concentrations indicated mainly short-term decreases in T3 and glucose in PHFWD chickens compared to early fed chickens, and no effects of PHFWD on T4 concentrations. Relative weights of liver, pancreas and heart were lower after PHFWD, but only in the first week of life. A retarded development of gut segments (duodenum, jejunum and ileum) was found in the first week of life, measured as shorter, lower relative weight, and lower villus height and crypt depth. It is concluded that 48 hours (≥36-60 hours) PHFWD leads to lower body weights and higher total mortality in chickens up to six weeks of age, the latter suggesting compromised chicken welfare, but effects of PHFWD on organ development and physiological status appear to be mainly short-term.

Project description:Broiler chicks usually hatch in the hatchery without access to feed and water until placement at the farm. This can affect their health and welfare negatively. Therefore, alternative strategies have been developed, for instance providing chicks with early nutrition in the hatchery or hatching eggs directly on-farm. However, information on the physical and mental welfare of chicks hatched in these systems compared to conventionally hatched chicks is limited. The aim of this study was to investigate the effects of alternative hatching systems on the welfare of broiler chickens in early and later life. A system comparison was performed with chickens that hatched conventionally in a hatchery (HH), in a system which provided light, feed, and water in a hatcher (hatchery-fed, HF), or on-farm (on-farm hatched, OH, where feed and water were available and transport of day-old chicks from the hatchery to the farm was not necessary). Chickens were reared in 3 batches, in 12 floor pens per batch (approximately 1,155 animals per pen), with a total of 12 replicates per treatment. Animal-based welfare indicators were assessed following standard protocols: plumage cleanliness, footpad dermatitis (FPD), hock burn, skin lesions (all at day 21 and 35 of age), and gait score (day 35). Furthermore, a set of behavioral tests was carried out: novel environment (day 1 and 21), tonic immobility, novel object, and avoidance distance test (day 4 and 35). Plumage cleanliness, hock burn, and skin lesions were affected by age but not by hatching system, with older broilers scoring worse than younger ones (P < 0.05). An effect of hatching system was only found for FPD, with the highest prevalence in HH chickens, followed by HF and OH chickens (P < 0.05). All responses measured in the behavioral tests were affected by age but not by hatching system. In later life, chickens were significantly less fearful than during the first days of life. The results indicate that conventionally hatched chickens scored significantly worse for FPD, whereas, in general, hatching system seemed to have minor effects on other broiler welfare indicators.

Project description:Campylobacter jejuni is the leading cause of bacterial food-borne infection; chicken meat is its main source. C. jejuni is considered commensal in chickens based on experimental models unrepresentative of commercial production. Here we show that the paradigm of Campylobacter commensalism in the chicken is flawed. Through experimental infection of four commercial breeds of broiler chickens, we show that breed has a significant effect on C. jejuni infection and the immune response of the animals, although these factors have limited impact on the number of bacteria in chicken ceca. All breeds mounted an innate immune response. In some breeds, this response declined when interleukin-10 was expressed, consistent with regulation of the intestinal inflammatory response, and these birds remained healthy. In another breed, there was a prolonged inflammatory response, evidence of damage to gut mucosa, and diarrhea. We show that bird type has a major impact on infection biology of C. jejuni. In some breeds, infection leads to disease, and the bacterium cannot be considered a harmless commensal. These findings have implications for the welfare of chickens in commercial production where C. jejuni infection is a persistent problem. Importance: Campylobacter jejuni is the most common cause of food-borne bacterial diarrheal disease in the developed world. Chicken is the most common source of infection. C. jejuni infection of chickens had previously not been considered to cause disease, and it was thought that C. jejuni was part of the normal microbiota of birds. In this work, we show that modern rapidly growing chicken breeds used in intensive production systems have a strong inflammatory response to C. jejuni infection that can lead to diarrhea, which, in turn, leads to damage to the feet and legs on the birds due to standing on wet litter. The response and level of disease varied between breeds and is related to regulation of the inflammatory immune response. These findings challenge the paradigm that C. jejuni is a harmless commensal of chickens and that C. jejuni infection may have substantial impact on animal health and welfare in intensive poultry production:

Project description:BackgroundA meta-analysis was conducted to assess dietary inorganic chromium supplementation on broiler growth performance and determine if these effects are regulated by strains, sex, or contextual factors such as study area and time.MethodsEligible studies were identified by searching Web of Science, Springer, Elsevier, Science Direct, Taylor & Francis online databases. The weighted average difference with corresponding 95% confidence interval was computed with a random-effects model. We performed subgroup analyses stratified by study locations, published years, broiler sex, and strains. The publication bias was assessed with Egger's test method. A total of nine studies were eligible for inclusion.ResultsThe meta-analysis results indicated that inorganic chromium supplementation significantly improved the broiler's growth performance, with a lower feed conversion ratio (FCR) and a higher average daily feed intake (ADFI). Through subgroup analyses, we found that the result of average daily gain (ADG) in Iran or published in the 2010s, the results of ADFI in Egypt, and the results of FCR in China had significant responses to chromium supplementation. We also found that Cobb 500 broilers and male broilers might be more sensitive to the addition of inorganic chromium by subgroup analyses. A model was used to obtain the amount of chromium addition under the optimal growth performance. The results showed that the adjusted ADFI and FCR presented a quadratic relationship with chromium supplementation except for average daily gain (ADG). The growth performance improved when the inorganic chromium addition ranged from 1.6 to 2.3 mg/kg. The result of sensitivity analyses showed low sensitivity and high stability. Also, there was little indication of publication bias for studies.ConclusionsOur study showed that the males and Cobb 500 broilers might be more sensitive to chromium supplementation and provided more accurate inorganic chromium supplementation for broiler management practice. The fewer included studies may lead to higher heterogeneity, and no subgroup analyses of environmental stress conditions was conducted due to the lack of related information. Therefore, this study still has some limitations, and we look forward to the follow-up researches.

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Meta-analysis of the effects of intensive rearing environments on the performance and welfare of broiler chickens.

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Meta-analysis of the effects of intensive rearing environments on the performance and welfare of broiler chickens.

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