Heat stress as a predisposing factor for necrotic enteritis in broiler chicks.

Heat stress is a physical environmental stressor, which can affect performance, health and welfare of poultry. The present study investigates the effect of cyclic acute heat stress as a predisposing factor for necrotic enteritis in broiler chicks in an experimental challenge model. Two hundred and forty broiler chicks were randomly allocated to four treatment groups, as follows: group A served as negative control (25°C), group B birds were subjected to cyclic acute heat stress (35°C), group C birds were challenged and group D birds were both subjected to heat stress and challenged. From each bird, the intestine, gizzard and liver were collected and scored for gross lesions. The intestinal digesta was collected for pH and viscosity determination. One caecum from each bird was taken for microbiological analysis. The statistical analysis and evaluation of data revealed that the heat stress in challenged birds showed a relative trend to increase the severity and the incidence of necrotic enteritis lesions, although it was not considered as statistically significant (Ρ = 0.077). Additionally, the heat stress induced necrotic enteritis outbreak in unchallenged birds; the challenge of birds as well as its combination with the heat stress affected significantly (Ρ ≤ 0.05) the pH and viscosity of intestinal digesta and the caecal Clostridium perfringens counts. The study provides evidence that cyclic acute heat stress is an environmental stressor, which can significantly affect necrotic enteritis and gut health, and thus should be taken into account in warmer areas of the world where poultry farming becomes a major industry.

The effect of cold stress on the pathogenesis of necrotic enteritis in broiler chicks.

Cold stress is a physical environmental stressor with significant effect on the poultry industry. The aim of the present study was to investigate the effect of cold stress as a predisposing factor for necrotic enteritis in broiler chicks. The experimental challenge model included an oral inoculation with 10-fold dose of attenuated anticoccidial vaccine and multiple oral inoculations with a specific strain of Clostridium perfringens. Birds were either challenged or not as described above, and either exposed or not to repeated cold stress (15°C for 12 h/day for 4 days). From each bird, intestinal gross lesions were scored and intestinal digesta pH and viscosity were measured. C. perfringens was counted in the caecum. The statistical analysis and evaluation of the experimental data revealed that the cold stress in challenged birds significantly increased the incidence and the severity of necrotic enteritis lesions (Ρ ≤ 0.05), while causing no lesions in unchallenged birds. Moreover, the cold stress caused a significant increase (Ρ ≤ 0.05) in the pH and C. perfringens counts in the caeca. The study provides evidence that cold stress increased the susceptibility to necrotic enteritis in a subclinical experimental model and thus should be regarded as a physical environmental stressor that could significantly affect the welfare, health and intestinal ecosystem of broiler chicks.

High stocking density as a predisposing factor for necrotic enteritis in broiler chicks.

Stocking density is a management factor which has critical implications for the poultry industry. The aim of the present study was to investigate the effect of high stocking density as a predisposing factor in an experimental model of necrotic enteritis in broiler chicks. The experimental challenge model included an oral inoculation with 10-fold dose of attenuated anticoccidial vaccine and multiple oral inoculations with a specific strain of Clostridium perfringens. Two hundred and forty as hatched day-old broiler chicks were randomly allocated to four treatment groups according to the following experimental design: group N, with normal stocking density (15 birds/m(2)) and no challenge; group D, with high stocking density (30 birds/m(2)) and no challenge; group P, with normal stocking density and positive challenge; and group DP, with high stocking density and positive challenge. From each bird, the intestine, gizzard and liver were collected and scored for gross lesions. The intestinal digesta was collected for pH and viscosity determination. One caecum from each bird was taken for microbiological analysis. The statistical analysis and evaluation of the experimental data revealed significant interaction effects between "stocking density" and "challenge", regarding gross lesion scores in intestine and liver, pH values in jejunum, ileum and caeca as well as C. perfringens counts in the caeca (P ≤ 0.05). High stocking density in challenged birds increased the gross lesion score in the intestine (P ≤ 0.05), contrary to unchallenged birds. It can be concluded that high stocking density affects unfavourably the welfare and gut health of broiler chicks, predisposes to necrotic enteritis in a subclinical experimental model and increases further its importance as a management factor for the poultry industry.

Temporary feed restriction partially protects broilers from necrotic enteritis.

The objective of this study was to investigate the effect of feed restriction on the intestinal ecosystem and on the pathogenesis of experimental necrotic enteritis in broiler chicks. To induce subclinical necrotic enteritis, an experimental challenge model using a specific diet formulation, Gumboro vaccination, oral inoculation of broilers with a 10-fold dose of attenuated anticoccidial vaccine and multiple oral inoculations with a specific strain of Clostridium perfringens was adopted. Two hundred and forty 1-day-old Cobb 500 broilers were randomly allocated to four groups: feed restricted, challenged, both feed restricted and challenged, and negative control. At 21, 22, 23 and 24 days of age, the intestines, gizzard and liver were collected from 15 birds in each group and scored for gross lesions. The intestinal digesta was collected for pH and viscosity determination. One caecum from each bird was taken for microbiological analysis. The application of feed restriction in birds challenged with C. perfringens reduced the necrotic enteritis lesion score significantly (P ≤ 0.05) and feed restriction significantly reduced (P ≤ 0.05) pH in the small intestine, the viscosity of the jejunum digesta as well as the C. perfringens counts in the caeca compared with the controls. In conclusion, feed restriction of broilers has a positive effect on the intestinal ecosystem and a significant protective effect against necrotic enteritis in the subclinical experimental model.

The role of an attenuated anticoccidial vaccine on the intestinal ecosystem and on the pathogenesis of experimental necrotic enteritis in broiler chickens.

The objective of the present study was to investigate the effect of an attenuated anticoccidial vaccination on the intestinal ecosystem and on the pathogenesis of experimental necrotic enteritis (NE) in broiler chickens. Two hundred and forty 1-day-old Cobb 500 broiler chickens were randomly allocated to four treatment groups according to the following experimental design: control Group N; Group PN, where birds were vaccinated with anticoccidial vaccine; Group M, where birds were challenged with Clostridium perfringens and with Eimeria maxima; and Group PM, where birds were both vaccinated and challenged. From each bird, the intestine, gizzard and liver were scored for gross NE lesions. Intestinal digesta were collected for pH and viscosity determination. Samples from the gastrointestinal tract and liver were taken for microbiological analysis. Evaluation of the experimental data revealed that Group M had significantly higher overall mean NE intestinal lesions compared with Group PM. Viscosity values of jejunum digesta as well as pH values of the duodenum, jejunum and ileum digesta in Group M were significantly lower compared with Group PM. C. perfringens counts in the caeca of Group PM were significantly lower compared with Group M. The milder decrease of pH and viscosity values of intestinal content and the reduction of C. perfringens counts in the caeca in challenged and vaccinated birds may explain the lower score of NE gross intestinal lesions and may suggest a positive effect on intestinal ecosystem and a significant protective effect of attenuated anticoccidial vaccination against NE in a subclinical experimental model.

Effect of rhythmic gymnastics on volumetric bone mineral density and bone geometry in premenarcheal female athletes and controls.

CONTEXT AND OBJECTIVE: Weight-bearing exercise during growth exerts positive effects on the skeleton. Our objective was to test the hypothesis that long-term elite rhythmic gymnastics exerts positive effects on volumetric bone mineral density and geometry and to determine whether exercise-induced bone adaptation is associated with increased periosteal bone formation or medullary contraction using tibial peripheral quantitative computed tomography and bone turnover markers. DESIGN AND SETTING: We conducted a cross-sectional study at a tertiary center. SUBJECTS: We studied 26 elite premenarcheal female rhythmic gymnasts (RG) and 23 female controls, aged 9-13 yr. MAIN OUTCOME MEASURES: We measured bone age, volumetric bone mineral density, bone mineral content (BMC), cortical thickness, cortical and trabecular area, and polar stress strength index (SSIp) by peripheral quantitative computed tomography of the left tibia proximal to the distal metaphysis (trabecular) at 14, 38 (cortical), and 66% (muscle mass) from the distal end and bone turnover markers. RESULTS: The two groups were comparable according to height and chronological and bone age. After weight adjustment, cortical BMC, area, and thickness at 38% were significantly higher in RG (P < 0.005-0.001). Periosteal circumference, SSIp, and muscle area were higher in RG (P < 0.01-0.001). Muscle area was significantly associated with cortical BMC, area, and SSIp, whereas years of training showed positive association with cortical BMC, area, and thickness independent of chronological age. CONCLUSIONS: RG in premenarcheal girls may induce positive adaptations on the skeleton, especially in cortical bone. Increased duration of exercise is associated with a positive response of bone geometry.