The proliferation of rearing systems providing opportunities for birds to engage in natural behaviors can trigger behavioral repertoires that when not manageable compromise animal welfare and the economic viability of the flock. Smothering in laying hens has long been perceived as “natural” or the result of hysteria among birds in the flock. However, the current literature has recognized smothering as an abnormal outcome with the potential to result in significant losses in cage-free poultry systems. Recent studies have specifically aimed to categorize the organization of smothering behavior and highlight its potential causes and consequences. In this study, literature review and bibliographic mapping, drawing on published articles and engagement with poultry farmers through extension and rural technical assistance, were employed. The findings indicate that smothering is a behavior triggered by factors related to the environment in which the laying hens are kept. This study concludes that there is a critical need for more rigorous and detailed research to elucidate the nuances of avian behavioral physiology and assess the impact of production systems on animal welfare and the economic impacts on the flock. This research contributes to a deeper understanding of bird behavior in high-production environments and provides practical insights for the poultry industry.

Although it is well known that incubation environment has a great in fluence on embryogenesis and post-hatching performance of birds, not much is known about how external thermal, sound and light stimuli are isolated by eggshells and perceived by embryos. In this context, this study aimed to develop, calibrate and evaluate a multilevel sensor for integrated monitoring of the external (incubator) and internal environment of eggs. The variables of interest for the external environment were air temperature and relative humidity. For the internal environment, shell temperature, internal temperature, luminosity and sound pressure level were considered. The sensor was developed with an ATmega328 microcontroller, in open-source prototyping, using electronic components which are compatible with the egg 's physical structure. Calibrations were carried out in a controlled environment, comparing the multilevel sensor with commercial equipment, obtaining coefficients of determination of R-2 > 0.90 for all variables studied. The multilevel sensor was also validated, simulating a commercial incubation situation and comparing eggs with 2 shell colors (white and brown) and internal volume (intact and empty). Validation results showed that white-shelled eggs insulate less external light ( P < 0.001) and full eggs presented higher internal temperatures, greater light and lower sound pressure levels compared to empty eggs ( P < 0.001). The multilevel sensor developed here is an innovative proposal for monitoring, simultaneously and in real time, different variables of interest in the commercial incubation environment.

This study evaluated how breeder age influences egg traits, embryonic development, and post-hatch thermoregulatory responses in broilers reared under thermoneutral conditions. Fertile Cobb 500® eggs from 34- and 63-week-old breeders were incubated under standardized conditions in a split-plot design (breeder age × incubation day: 0, 7, 14, and 18 d; n = 160). Initial (IW) and final egg weight (FW), embryo weight (EW), ratio between net internal egg weight and embryo weight (NW/E) and embryo length (EL) were recorded. A second experiment reared chicks from the same breeder ages to 42 d in a completely randomized 7 × 2 factorial design (week of age × breeder age; n = 48), with weekly measurements of body weight (BW), respiratory rate (RR), cloacal temperature (CT) and surface temperatures (back, head, eye, wing, and foot). Eggs from 63-wk breeders showed greater IW and FW (p < 0.001) and higher NW/E (p < 0.01). EW and EL increased with incubation day (p=0.026 and p=0.004, respectively), with breeder age × day interactions (EW: p = 0.001; EL: p = 0.009). Factor analysis consistently yielded two components representing egg size/reserves (IW, FW, and NW/E) and embryonic growth (EW and EL) in both breeder age groups. Post-hatch, RR was influenced by breeder age (p = 0.04), week (p < 0.001) and their interaction (p = 0.001), whereas EyeT showed modest breeder-age effects (p = 0.01). CT, HeadT and WingT remained stable (p> 0.05). BW was affected only by week (p < 0.001), with no effect of breeder age (p = 0.95) or interaction (p = 0.99). CHAID decision trees highlighted IW (incubation) and BW (post-hatch) as the primary split variables. Practically, breeder age should primarily guide egg grading and incubation management, whereas broilers from young and old breeders can be managed similarly in the grow-out phase under adequate thermal conditions.