Dietary supplementation with sodium butyrate: live performances, carcass traits and myopathy occurrence in female and male broilers

The present study aimed to evaluate the effect of different inclusion levels of sodium butyrate in diets with two fat levels on growth performances and myopathies occurrence in broiler chickens of both sexes. A total of 900 one-day-old chicks (Ross 308) were allocated to 36 pens according to a 2 × 3 × 2 factorial design encompassing two fat inclusion levels (lower fat-grower diet: 6.7%; finisher diet 7.7%: and higher fat-grower diet: 7.7%; finisher diet: 8.9%), three levels of microencapsulated sodium butyrate (0 mg/kg, 150 mg/kg and 300 mg/kg) and two sexes (3 pens per experimental group). As expected, a higher fat diet resulted in greater body weight (P<0.001), average daily gain (P<0.001), and better feed conversion ratio (P<0.001) compared to chickens fed a lower fat diet, whereas feed intake was not affected (P>0.10). The chickens fed a higher fat diet had higher cold carcass weight (P<0.01) and dressing percentage (P<0.05), and greater Pectoralis major yield (P<0.05) in comparison with birds fed a lower fat diet. Sodium butyrate supplementation did not affect growth performance nor slaughter yield and carcass traits (P>0.05). Compared to males, female chickens had lower body weight, weight gain, and feed intake (P<0.001) and worse feed conversion rate (P<0.001). In addition, females had higher dressing percentage (P<0.001), and greater breast and P. major yields (P<0.001) in comparison with males. Furthermore, no interactions between sodium butyrate and fat inclusion level, nor sodium butyrate and sex were observed. At gross examination, regardless of the experimental factors, the occurrence of myopathies was 56.25% for white striping (WS), 24.31% for wooden breast (WB), and 7.64% for spaghetti meat (SM). The occurrence of WB was higher in males than in females (18.75% vs. 5.56%; P<0.01), whereas SM showed an opposite trend (6.94% in females vs. 0.69% in males; P<0.05). Moreover, the high-fat diet increased the occurrence of WS (34.72% vs. 21.53%; P < 0.01) and SM (6.94 vs. 0.69%; P<0.05). Finally, the overall occurrence of WS, WB, and SM were not affected (P>0.05) by the butyrate addition. In conclusion, sex and dietary fat level affected the growth and myopathy occurrence. In contrast, butyrate did not modify performances and breast abnormalities, while effects at the gut level have to be investigated. Funding: The grant of M. Boskovic Cabrol was supported by the DEMyo project (No 101063055) funded by the European Commission under the HORIZON-MSCA-2021-PF-01 call.