The effect of light regime and time of slaughter in broiler on broiler performance, liver antioxidant status, and expression of genes related to peptide absorption in the jejunum and melatonin synthesis in the brain.

This study aimed to assess the effects of light regime and time of slaughter on primal cut and organ weights, peptide transporter 1 (PEPT1) gene expression in the jejunum, arylalkylamine N-acetyltransferase (AANAT) gene expression in the brain, and liver oxidant/antioxidant status in broilers aged 37 days. The experiment was conducted in a factorial completely randomized design, with two light regimes (intermittent light varying according to bird age and continuous light under an 18 h light/6 h dark photoperiod) and four times of slaughter (2:00, 8:00, 14:00 and 20:00 h). There was an interaction effect on PEPT1 and AANAT expression, lipid and protein oxidation and superoxide dismutase (SOD) activity. In both light regimes, PEPT1 expression responded cubically to slaughter time. In the continuous light group, PEPT1 expression was highest in birds slaughtered at 2:00 and 14:00 h, whereas, in the intermittent light treatment, expression was highest at 8:00 h. In the continuous light regime, AANAT expression had a cubic relationship with time of slaughter, with the greatest values recorded at 20:00 h. In the intermittent light regime, slaughter time showed a cubic effect on lipid oxidation, which was highest at 8:00 h. In the continuous light group, there was a cubic effect on nitrite concentration, lipid oxidation, protein oxidation, and SOD activity; nitrite levels, lipid oxidation, and protein oxidation were highest and SOD activity was lowest in birds slaughtered at 14:00 h. Time of slaughter influenced catalase activity, which responded cubically; catalase activity was lowest at 8:00 and 14:00 h. This study is the first to demonstrate that PEPT1 expression in the jejunum of broilers follows a diurnal rhythm and varies according to light regime. The results also suggest that mainly continuous lighting and slaughter at 14:00 h when the animals are possibly more active may be more stressful to broilers.

Characterization and Strength Quality of the Oryctolagus cuniculus Leather Compared to Oreochromis niloticus Leather.

This study aimed to compare the resistance of the Oryctolagus cuniculus L. (rabbit) and Oreochromis niloticus L. (Nile tilapia) skins, as well as to observe the design of the flower of these skins and the morphology of the dermis. Tilapia and rabbit skins were placed inside the same equipment (tannery machine) for the chromium salt tanning process. The flower design of the fish leather distinguishes it from the rabbit leather, the latter being constituted by the opening of the hair follicles and pores, while the fish leather is constituted by the presence of protective lamellae and insertion of the scales. The dermis of rabbit skin consists of thick bundles of collagen fibers arranged in all directions, which differs from the morphology observed in the dermis of fish skin. However, in the Nile tilapia skin dermis, overlapping and parallel layers of longitudinal collagen fiber bundles are observed, these layers are interspersed with fiber bundles crossing the sking surface (transversely), tying the fibers together and providing greater strength, which can be proven by the strength test. The fish leathers, despite having less thickness (1.0 mm), demonstrated significantly greater tensile strength (13.52 ± 1.86 N mm-2) and tear strength (53.85 ± 6.66 N mm-2) than rabbit leathers, that is, (8.98 ± 2.67 N mm-2) and (24.25 ± 4.34 N mm-2). However, rabbit leather demonstrated higher elasticity (109.97 ± 13.52%) compared to Nile tilapia leather (78.97 ± 8.40%). It can be concluded that although the rabbit leather is thicker due to the histological architecture of the dermis (thick bundles of collagen fibers arranged in all directions with no pattern of organization of collagen fibers), it shows less resistance than Nile tilapia leather, which demonstrates an organization of overlapping and parallel layers and intercalating collagen fiber bundles transversally to the surface, functioning as tendons for the swimming process. It is recommended to use a piece of fabric (lining) together with the fleshy side of the rabbit leather, to increase resistance when used in clothing and footwear, as these products require greater tensile strength. Thus, it minimizes this restriction for the use of rabbit leather in the aforementioned purposes.