The present study aimed to evaluate how dietary supplementation with a microencapsulated sodium butyrate (500 mg/kg; 30% Na-butyrate) in 768 male and female broiler chickens affected growth performance, jejunum gut morphology and caecal microbiome at different ages (11, 24, and 35 d), slaughter results, meat quality, and myopathy (white striping, wooden breast, and spaghetti meat) occurrence. No health problem was recorded (mortality < 1%) and Na-butyrate supplementation did not affect performance throughout the trial, nor did it affect gut morphology or microbiota composition and abundance at different ages. Additionally, dietary treatment did not affect slaughter results, meat quality, or myopathy rate, whereas the rate of females affected by spaghetti meat tended to be higher in those fed the control compared with the Na-butyrate diet (33.3% versus 16.7%; p ¼ .06). Moreover, males showed a higher wooden breast (21.9% versus 7.3%; p .01) and a lower spaghetti meat (3.1% versus 25.0%; p .001) rate compared with females. Finally, the richness index (i.e. the number of different species represented in an ecological community, landscape, or region) in the caecum increased (p .001) with increasing chicken age, and the community composition was also affected (adonis p .001). In conclusions, under the good health condition of the present trial, the tested Nabutyrate had no effect on performance and gut response at different ages of broiler chickens. Moreover, the occurrence of spaghetti meat and wooden breast differed between males and females. HIGHLIGHTS Under optimal health conditions, Na-butyrate supplementation did not affect performance or gut response at different ages of broiler chickens. Males showed a significantly higher occurrence of wooden breasts, whereas females had higher rates of spaghetti meat. In females, the Na-butyrate supplementation tended to reduce the occurrence of spaghetti meat.
Under intensive rearing conditions, the welfare of broiler chickens may be at risk depending on genotype and sex, due to their different growth rates. The practice of quantitative feed restriction may also impact on welfare. This study aimed to evaluate behaviour and corticosterone content in plasma and faeces at different ages using 896 one-day-old chicks housed in 32 pens, allocated to 8 groups, i.e., 2 genotypes (standard vs. high breast yield) × 2 sex × 2 feeding plans (ad libitum vs. restricted, AL vs. FR). The feeding system affected the percentage of standing (9.84% vs. 11.7% in AL vs. FR; p ≤ 0.001), feeding (7.51% vs. 8.17%; p ≤ 0.01) and sitting/lying (67.0% vs. 64.1%; p ≤ 0.001), and the faeces corticosterone content (12.2 vs. 13.6 ng/g in AL vs. FR; p ≤ 0.10). Sex affected the percentage of pecking other chickens, standing and comfort behaviours. Changes in behaviour were recorded between high and standard breast yield genotypes with faeces corticosterone which tended to be higher in the former (p ≤ 0.10). Significant interactions between the main factors and age were observed. Major changes in behaviour were due to feed restriction, which stimulated activity during restriction.
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