Puberty and growth rate in thoroughbred fillies

Puberty and growth rate in thoroughbred fillies

Autor Nogueira, G. P. Google Scholar
Barnabe, R. C. Google Scholar
Verreschi, ITN Google Scholar
Instituição Universidade de São Paulo (USP)
Universidade Federal de São Paulo (UNIFESP)
Resumo We measured progesterone and estradiol levels from birth to the beginning of adult life in 10 Thoroughbred fillies from the Equilia Stud Farm in Avare SP, Brasil. the animals were measured and weighed monthly for the determination of body development and of a possible correlation between the rate of weight and height gain and the onset of detectable sex hormone levels. Jugular blood was collected twice a week and stored at -20 degrees C until assay of progesterone by a solid phase RIA with a sensitivity of 0.32 nmol/L and of estradiol by liquid phase RIA adapted to low levels (3.67 pmol/L). the fillies were born with high serum levels of both hormones,which fell to undetectable levels by the first week of life. A variation in growth rate was observed, with the highest levels occuring from birth to the 3rd month of life, followed by a reduction until 15 mo of life, when fast growth was resumed. the monthly weight gain was 1.5% when the fillies reached puberty and 5.4% during the next month, (P<0.05, Friedman test). During this second period of accelerated growth after the beginning of progesterone production at detectable levels (above 0.318 nmol/L), the parameters of skeletal growth did not differ (P>0.05). the month of onset of puberty was the month of lowest weight gain in the life of the fillies, and it coincided with the highest insolation period. in conclusion, horses, like all other developed vertebrates, have a double pattern of development, with the acceleration observed at puberty depending on sex steroids, which in turn coincides with the highest insolation period. Gonadal activity characterized by serum progesterone levels was low from birth to the onset of puberty. After puberty the progesterone cycles were similar to those of adult animals with a mature hypothalamic-gonadal axis. (C) 1997 by Elsevier Science Inc.
Palavra-chave puberty
sex hormones
Idioma Inglês
Data de publicação 1997-09-01
Publicado em Theriogenology. New York: Elsevier B.V., v. 48, n. 4, p. 581-588, 1997.
ISSN 0093-691X (Sherpa/Romeo, fator de impacto)
Publicador Elsevier B.V.
Extensão 581-588
Direito de acesso Acesso restrito
Tipo Artigo
Web of Science WOS:A1997XU04200008
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