#Incubator egg skin#

The amount of VIP was significantly higher in the ME and cell bodies in the medial basal hypothalamus in incubating as compared to actively laying hens ( Sharp et al., 1989). On the other hand, disruption of incubation behavior with anti-VIP was prevented by concomitant administration of ovine PRL ( Sharp et al., 1989). Daily injections of anti-VIP caused incubating bantam hens to desert their nests. Immunization against VIP inhibits PRL secretion in bantam hens ( Sharp, Sterling, Talbot, & Huskisson, 1989) and turkeys ( El Halawani, Pitts, Sun, Silsby, & Sivanandan, 1996). Both chicken and turkey VIP cDNAs have been sequenced ( Talbot, Dunn, Wilson, Sang, & Sharp, 1995 You, Silsby, Farris, Foster, & El Halawani, 1995). The structure of hypothalamic chicken and turkey VIP is regarded as the same as that isolated from the chicken gut, which is a 28-amino-acid peptide differing from mammalian VIP in four amino acids ( Nilsson, 1975). Mammalian VIP specifically stimulated PRL release in vivo and in vitro in bantam hens ( Macnamee, Sharp, Lea, Sterling, & Harvey, 1986) and turkeys ( Opel & Proudman, 1988 Proudman & Opel, 1988), while immunohistochemical studies showed the presence of VIP-ir nerve terminals in the ME in quail ( Yamada, Mikami, & Yanaihara, 1982), bantam hens ( Macnamee et al., 1986), and pigeons ( Péczely & Kiss, 1988). In birds, PRL secretion is actively stimulated by release of VIP from the ME. It has been suggested that in female turkeys the action of PRL on incubation behavior is facilitated by the combined action of E 2 and P 4 ( El Halawani, Silsby, Behnke, & Fehrer, 1986). In these birds, plasma levels of PRL do not rise during egg-laying and the early part of incubation but are high at the end of incubation and when the squabs are being fed ( Goldsmith, Edwards, Koprucu, & Silver, 1981). In ring doves and other Columbiformes, PRL causes growth of the crop gland and production of crop milk for feeding of young for the first few days after hatch. In species that produce altricial young, PRL is also very high during incubation but it often stays high whilst the young are fed in the nest (canary ( Goldsmith, 1982)). In female birds that fail to incubate, as well as in males, PRL never rises above baseline concentrations (mallards ( Goldsmith & Williams, 1980)). In species that hatch precocial young, PRL levels rise slightly during egg-laying, but then increase markedly throughout incubation and fall immediately when the chicks have hatched. Injections of PRL induce chickens to incubate eggs ( Riddle, Bates, & Lahr, 1935 Sharp, Macnamee, Sterling, Lea, & Pedersen, 1988), and maintain readiness of ring doves to incubate their clutches ( Lehrman & Brody, 1964 Janik & Buntin, 1985). Estrogens and P 4 are the active agents in the female, but where males incubate these are replaced by androgens.

The whole process is thought to be controlled by a synergism between PRL and the sex steroids ( Jones, 1971 Drent, 1975).

#Incubator egg skin#

The changes in the brood pouch skin are substantial, involving hyperplasia of the epidermis, an edema leading to wrinkling of the skin, and extra vascularization. Brood patches develop in virtually all birds and seem to be used to transfer body heat to the eggs. Bentley, in Hormones and Reproduction of Vertebrates: Birds, 2011 5 Mechanisms and Pathways Regulating Prolactin (PRL) SecretionĪ period of egg incubation occurs in the vast majority of birds ( Drent, 1975).