Heng-Wei Cheng

The objective of this study was to evaluate the effects of photoperiod on meat quality, oxidative stability, and metabolites of broiler fillet (M. Pectoralis major) muscles. A total of 432 broilers was split among 4 photoperiod treatments [hours light(L):dark(D)]: 20L:4D, 18L:6D, 16L:8D, and 12L:12D. At 42 days, a total of 48 broilers (12 broilers/treatment) was randomly selected and harvested. At 1 day postmortem, fillet muscles were dissected and displayed for 7 days. No considerable impacts of photoperiods on general carcass and meat quality attributes, such as carcass weight, yield, pH, water-holding capacity, and shear force, were found (p > 0.05). However, color and oxidative stability were influenced by the photoperiod, where muscles from 20L:4D appeared lighter and more discolored, coupled with higher lipid oxidation (p < 0.05) and protein denaturation (p = 0.058) compared to 12L:12D. The UPLC–MS metabolomics identified that 20 metabolites were different between the 20L:4D and 12L:12D groups, and 15 were tentatively identified. In general, lower aromatic amino acids/dipeptides, and higher oxidized glutathione and guanine/methylated guanosine were observed in 20L:4D. These results suggest that a photoperiod would result in no considerable impact on initial meat quality, but extended photoperiods might negatively impact oxidative stability through an alteration of the muscle metabolites.

Intestinal bacteria release various neuroactive compounds directly or indirectly regulating brain function to modulate host health and behavior through the gut-brain axis. Probiotics have been used as dietary supplements to target gut microbiota (microbiome) for prevention or therapeutic treatment of various diseases including mental disorders. In our study, chickens were used as an animal model to assess, if dietary supplementation of probiotic, Bacillus subtilis, reduces aggressive behaviors following social challenge. Chickens of an aggressive line were housed in single-hen cages. At 24 weeks of age, the hens were paired with similar body weight to identify the dominance rank (day 0). The subordinate and dominant of each pair were fed a regular layer diet or the diet mixed with 250 ppm probiotics for 2 weeks, then the second behavior test was performed between the same pair (day 14). The display of aggressive behaviors in the regular diet-fed chickens was not affected between the levels at day 0 and day 14, while the frequency of threat and aggressive pecking were reduced in the probiotic-fed chickens compared to the levels at day 0. These results suggest dietary probiotic, Bacillus subtilis, could be a suitable strategy for increasing hosts’ mental health.