Eggs are a highly nutritious food and an excellent source of carotenoids, lutein and zeaxanthin, which contribute to antioxidant defenses and ocular health. However, eggs have been viewed skeptically because of their impact on serum cholesterol levels. This review summarizes the evidence from clinical trials, observational studies, and worldwide ecological studies relating egg consumption to serum lipid profiles, antioxidant status, and cardiovascular outcomes. Recent meta-analyses on egg consumption have reported an increase in serum cholesterol but limited or no impact on atherosclerosis and cardiovascular disease risk. Clinical studies have reported that the additional consumption of an egg per day for 4 weeks improved high-density lipoprotein-cholesterol levels and decreased oxidized low-density lipoprotein levels. Most recently, a cross-sectional study of Japanese patients who underwent coronary angiography reported no significant association between egg intake and the prevalence of coronary artery disease or multi-vessel disease. Among patients not receiving lipid-lowering drugs, moderate egg intake (3–4 eggs/week) was associated with a lower prevalence of multi-vessel disease. Furthermore, worldwide ecological analyses have identified a significant negative association between egg intake and the incidence and mortality of ischemic heart disease. Given their high nutritional value, relatively low cost, and the evidence presented, eggs could contribute to healthy diets in many countries worldwide.

Poultry sperm survive for extended periods within sperm storage tubules (SSTs) located at the uterovaginal junction (UVJ) of the oviduct, and their survival period is directly correlated with fertility. In this review, the mechanisms underlying sperm longevity in SSTs are discussed, with a focus on recent discoveries related to the functions of SSTs and UVJ tissue. In particular, the possible role of fatty acids and exosomes secreted by SST cells in sperm survival are discussed. Subsequently, the importance of gonadal steroid receptors in maintaining the integrity and function of the SSTs is described. Additionally, the role of the local immune system in protecting sperm from infection and facilitating the selection of high-quality sperm is discussed. Disruption of these SST functions may result in reduced fertility. This review provides updated information on the mechanisms that enable prolonged sperm survival in SSTs.

Poultry meat and eggs are important sources of high-quality animal protein worldwide. However, poultry in Japan has historically been regarded as a symbolic or spiritual entity more than as a food source, as its roles are deeply embedded in Japanese consciousness and society.Current evidence indicates that chickens first appeared in Japan during the Yayoi period, approximately 2,000 years ago, coinciding with a period of active human migration to the Japanese archipelago. Since then, poultry has played notable roles in Japanese art, literature, mythology, and folktales.Recent advancements in molecular clock analysis or the detection of genomic modifications, such as introgression, deletions, mutations, and viral infection from trace fossil/live samples necessitate the continual revision and refinement of existing theories about human and animal history across several academic disciplines.Therefore, the objective of the present review was to elucidate the distinct and multilayered relationship between humans and poultry in Japan, incorporating recent anthropological and ornithological perspectives.

Regulation of food intake, especially during the neonatal period, is important to ensure optimal nutrition and meet the metabolic requirements of growing and healthy animals. However, many problems associated with neonatal chicks remain unsolved. Feeding behavior during the neonatal stage is characterized by short resting periods between very brief times spent taking up food. Accordingly, neuropeptides, which take time to synthesize and release, as well as nutrients that are taken up via feeding, may be involved in feeding regulation. The present review summarizes current knowledge about the role of amino acids and their interaction with neuropeptides on the regulation of food intake in neonatal chicks with special emphasis on L-arginine metabolism and neuropeptide Y. Fasting and subsequent short-term refeeding influence amino acid metabolism in the brain. Short-term refeeding induces a rapid increase in the concentrations of several amino acids, which may contribute to satiety signals in the neonatal chick brain. The function of L-arginine is related to its metabolite, L-ornithine, which acts as an innate satiety signal in the control of food intake. Co-injection with L-ornithine attenuates the orexigenic effect of neuropeptide Y in a dose-dependent manner. This implies a potent interaction in the brain between the regulation of food intake by neuropeptide Y and acute satiety signals by L-ornithine. The roles of other amino acids in feeding and their relationship with the stress response are also discussed in this review. In conclusion, endogenous neuropeptides and endogenous and/or exogenous nutrients such as amino acids are believed to coordinate the feeding behavior of neonatal chicks.

Leptin, a key regulator of reproductive physiology, influences various processes in vertebrates, including oocyte proliferation, embryogenesis, the onset of puberty, ovarian function, and follicle development. In mammals, leptin affects steroidogenesis, folliculogenesis, and hormonal regulation through the hypothalamic-pituitary-gonadal axis. Instead, in avian species, leptin-controlled mechanisms are poorly understood, because birds do not produce leptin in adipocytes. In birds, leptin is expressed in the brain, pituitary glands, and gonads, where it enhances ovarian function and egg-laying performance, particularly during feed deprivation. In this review, we discuss and summarize the recently discovered role of leptin in regulating ovarian function during different life stages in birds and compare it with its function in mammals.