Photorefractoriness in birds and comparison with mammals

Nicholls, T. J.; Goldsmith, Arthur R.; Dawson, Alistair

doi:10.1152/physrev.1988.68.1.133

Cited by 479 publications

(339 citation statements)

References 0 publications

Supporting

Mentioning

321

Contrasting

Unclassified

Order By: Relevance

“…Follett, 1984; Stokkan and Sharp, 1984;Nicholls et al, 1988). Similar results have been found in some spring/summer breeders that reproduce at high latitudes but overwinter in the tropics (Tewary and Kumar, 1982; Kumar and Tewary, 1983;Tewary and Tripathi, 1983).…”

supporting

confidence: 53%

The development of photorefractoriness in termination of the breeding season in the tropical brahminy myna: role of photoperiod

Kumar¹,

Kumar²

1991

Reprod. Nutr. Dévelop.

View full text Add to dashboard Cite

supporting

confidence: 53%

The development of photorefractoriness in termination of the breeding season in the tropical brahminy myna: role of photoperiod

Kumar¹,

Kumar²

1991

Reprod. Nutr. Dévelop.

View full text Add to dashboard Cite

“…In fact, TH play an important function in the expression of endogenous seasonal rhythms of neuroendocrine reproductive activity in sheep, as in many species of birds (Nicholls et al, 1988b). Thyroidectomised ewes began their sexual season at the same time as intact animals, but continued to cycle when the intact ewes enter seasonal anoestrus (Nicholls et al, 1988a;Maurenbrecher and Barrell, 2003). Similar but less-pronounced effects have been obtained in sheep rendered hypothyroid, in which the end of the reproductive season occurred later than in controls (Follett and Potts, 1990; Hernandez et al, 2003).…”

Section: Seasonality Of Reproductionmentioning

confidence: 99%

Thyroid hormones in small ruminants: effects of endogenous, environmental and nutritional factors

Todini

2007

Animal

193

142

View full text Add to dashboard Cite

Appropriate thyroid gland function and thyroid hormone activity are considered crucial to sustain the productive performance in domestic animals (growth, milk or hair fibre production). Changes of blood thyroid hormone concentrations are an indirect measure of the changes in thyroid gland activity and circulating thyroid hormones can be considered as indicators of the metabolic and nutritional status of the animals. Thyroid hormones play a pivotal role in the mechanisms permitting the animals to live and breed in the surrounding environment. Variations in hormone bioactivity allow the animals to adapt their metabolic balance to different environmental conditions, changes in nutrient requirements and availability, and to homeorhetic changes during different physiological stages. This is particularly important in the free-ranging and grazing animals, such as traditionally reared small ruminants, whose main physiological functions (feed intake, reproduction, hair growth) are markedly seasonal. Many investigations dealt with the involvement of thyroid hormones in the expression of endogenous seasonal rhythms, such as reproduction and hair growth cycles in fibre-producing (wool, mohair, cashmere) sheep and goats. Important knowledge about the pattern of thyroid hormone metabolism and their role in ontogenetic development has been obtained from studies in the ovine foetus and in the newborn. Many endogenous (breed, age, gender, physiological state) and environmental factors (climate, season, with a primary role of nutrition) are able to affect thyroid activity and hormone concentrations in blood, acting at the level of hypothalamus, pituitary and/or thyroid gland, as well as on peripheral monodeiodination. Knowledge on such topics mirror physiological changes and possibly allows the monitoring and manipulation of thyroid physiology, in order to improve animal health, welfare and production.Keywords: goats, nutrition, seasons, sheep, thyroid hormones IntroductionAppropriate thyroid gland function and activity of thyroid hormones (TH) are considered crucial to sustain the productive performance in domestic animals (growth, milk, hair fibre production) and circulating TH can be considered as indicators of the metabolic and nutritional status of the animals (Riis and Madsen, 1985;Todini et al., 2007). Changes of blood TH concentrations are an indirect measure of the changes in thyroid gland activity. Many papers report marked seasonal variation in thyroid activity and in blood TH concentration. These hormone variations are particularly important in the free-ranging and grazing animals, whose main physiological functions (feed intake, reproduction, hair growth) are markedly seasonal. This is the case of small ruminants traditionally reared. Such variations in hormone concentration, in fact, allow the animals to adapt their metabolic balance to different environmental conditions, variations in nutrient requirements and availability, and to homeoretic changes during different physiological stages.The present paper aims to re...

show abstract

“…Avian reproduction occurs during determined periods of the year, it is synchronized with seasonal variations and it is often dependent of photoperiod (Nicholls et al 1988). In the domestic Quail and other bird species, there are studies correlating the effects of photoperiod with gonadal development, or with gonadal activity during the stages of testicular cycle, taking into account the variations of testicular weight during these stages (absolute or relative), (Tanaka et al 1964, Hamner 1966, Schwab 1970, Brillard & Reviers 1981, Hess & França 2008.…”

Section: Introductionmentioning

confidence: 99%

Aspects of spermatogenesis and microscopic testicular morphology in Greater Rhea, Rhea americana (Linnaeus, 1758)

2016

View full text Add to dashboard Cite

ABSTRACT.-Freneau G.E., Carvalho S.F.M., Saboia-Morais S.M. T. & Freneau B.N. 2016 The purpose of this study was to study the microscopic morphology of the testicular parenchyma of Rhea americana birds. Fifty-four 2.5±0.5 year-old male adults bred in captivity. were used. During commercial slaughter, samples of testis were collected in November respectively. Microscopic measures of seminiferous tubules, spermatic cells and diameter of the nuclei were presented. These data confirm reproductive seasonality, with breeding season in spring-summer with sperm production. A great variation n parenchyma, when compared breeding was noticeable.

show abstract

Photorefractoriness in birds and comparison with mammals

Cited by 479 publications

References 0 publications

The development of photorefractoriness in termination of the breeding season in the tropical brahminy myna: role of photoperiod

The development of photorefractoriness in termination of the breeding season in the tropical brahminy myna: role of photoperiod

Thyroid hormones in small ruminants: effects of endogenous, environmental and nutritional factors

Aspects of spermatogenesis and microscopic testicular morphology in Greater Rhea, Rhea americana (Linnaeus, 1758)

Contact Info

Product

Resources

About