Overcrowding stress decreases macrophage activity and increases Salmonella Enteritidis invasion in broiler chickens

Figures & data

Table 1. Effects of overcrowding stress (16 birds/m2) on the performance parameters of broiler chickens infected with Salmonella Enteritidis.

Performance parameter (per bird)	Group C	Group Ov	Group PC	Group POv
Body weight gain (kg)	2.54 ± 0.03	2.44 ± 0.05*	2.55 ± 0.04	2.39 ± 0.21*
Feed intake (kg)	4.58 ± 0.20	4.16 ± 0.20*	4.46 ± 0.25	4.71 ± 0.83*
Feed conversion	1.75 ± 0.08	1.65 ± 0.06	1.69 ± 0.11	1.91 ± 0.27* ^a

Results presented as mean ± standard deviation of five replicates (n = 5); in Groups C and CP, each replicate had 14 broiler chickens; in Groups Ov and POv, each replicate had 23 broiler chickens. Overcrowding stress was performed between ED₁ and ED₄₂. Data were collected between ED₁ and ED₄₂. Parametric data: two-way ANOVA followed by a Tukey test and one-way ANOVA followed by a Tukey test. *P < 0.01 compared with the respective control groups (Group C or Group PC). ^a P < 0.05 positive interaction between overcrowding stress and Salmonella infection.

Figure 1. Effects of overcrowding stress (16 birds/m²) on the corticosterone serum levels (pg/ml) in broiler chickens that were infected (Group POv) or not infected (Group Ov) with Salmonella Enteritidis. Data presented as mean ± standard deviation (n = 10/group). *P < 0.05 compared with the Control (Group C) and positive Salmonella control (Group PC) groups (two-way ANOVA followed by Tukey test).

Table 2. Effects of overcrowding stress (16 birds/m2) on the relative weight of the lymphoid organs and the plasma immunoglobulin concentration of broiler chickens infected with Salmonella Enteritidis.

Parameter	Group C	Group Ov	Group PC	Group POv
Spleen relative weight	0.087 ± 0.001	0.103 ± 0.002	0.105 ± 0.002	0.093 ± 0.002
Bursa relative weight	0.1869 ± 0.05	0.1724 ± 0.05*	0.1781 ± 0.05	0.1728 ± 0.05*
IgA (ng/ml)	169.90 ± 36.13	243.73 ± 122.32 ^†	240.49 ± 81.50 ^†	254.22 ± 67.41 ^†
IgM (ng/ml)	26.02 ± 5.76	28.54 ± 11.11	31.42 ± 11.92	44.62 ± 12.50 ^#
IgG (ng/ml)	990.98 ± 46.69	970.97 ± 38.63	1210.14 ± 34.00	780.47 ± 10.44 ^§

Results presented as mean ± standard deviation (n = 10); overcrowding stress were performed between ED₁ and ED_42. Samples were collected at ED₄₂. Parametric data: one-way ANOVA followed by a Tukey test. *P < 0.05 compared with the respective control groups (Group C or Group PC); ^† P < 0.05 compared with Group C. ^# P < 0.05 compared with all groups; ^§ P < 0.05 compared with Group PC.

Figure 2. Effects of overcrowding stress (16 birds/m²) on the basal oxidative burst (2A), the S. aureus-induced oxidative burst (2B), the percentage of phagocytosis (2C) and the intensity of phagocytosis (2D). Data presented as mean ± standard deviation (n = 10/group); different lowercase letters above the columns indicate statistically significant differences (P < 0.05, two-way ANOVA followed by Tukey test). Definitions of the groups are specified in Figure 1.

Figure 3. Effects of overcrowding stress (16 birds/m²) on Salmonella Enteritidis invasion of the liver. Data presented as mean ± standard deviation (n = 8/group). *P < 0.05 compared with the positive Salmonella control group (Group PC) (Mann–Whitney U test). CFU, colony-forming units.

Figure 4. Histology of the small intestine of broiler chickens. Haematoxylin and eosin staining. Scale bar = 20 µm. 4A: Duodenum mucosa from the control broiler chicken group (Group C). 4B: Duodenum mucosa from the overcrowding broiler chicken group (Group Ov), showing mild acute lympho-plasmacytic enteritis in the lamina propria (LP). 4C: Duodenum mucosa of the positive control broiler chicken group (Group PC) with mild acute lympho-plasmacytic enteritis and the presence of heterophils in the LP. 4D: Duodenum mucosa of the positive overcrowding broiler chicken group (Group POv), showing moderate acute lympho-plasmacytic enteritis in the LP. Black arrows, heterophilic foci.