ASSESSMENT OF DEVELOPMENT OF THE TESTES AND ACCESSORY-GLANDS BY ULTRASONOGRAPHY IN BULL CALVES AND ASSOCIATED ENDOCRINE CHANGES

The testes, prostate and vesicular glands of 10 bull calves were exami ned by ultrasonography every 2 wk from 2 to 46 wk of age, at which tim e the scrotal circumference (SC) of all the calves had reached puberta l size (28 cms). Computer-assisted image intensity analysis (numerical pixel values) was conducted. Blood samples were collected every other week from 2 to 46 wk of age. Testicular diameter increased in a linea r manner from 2 to 46 wk of age, but the diameter measured in a transv erse plane (caudal) was greater between 10 and 34 wk of age than when measured in a longitudinal (lateral) plane (P<0.05). Growth of the pro state and vesicular glands, based on dimensions, was linear, but vesic ular gland length increased more rapidly after 32 wk of age (P<0.05). Image intensity of the vesicular glands and prostate declined from bir th or 8 wk of age, respectively, to 14 wk of age, increased to 18 wk a nd then declined to a nadir at 30 wk, followed by a rapid increase to 34 wk of age for the vesicular glands and to 46 wk of age for the pros tate (P<0.05). Image intensity of the testes showed an early increase to 6 to 8 wk of age and a subsequent increase from about 20 wk of age to 46 wk of age, with an inflection at 30 wk of age (P<0.05). There wa s a transient increase in mean serum concentrations of LH between 6 an d 20 wk of age (P<0.05), and LH concentrations appeared to increase ag ain after 36 wk of age (P>0.05). Mean serum concentrations of FSH decl ined with age (P<0.05). Mean serum concentrations of testosterone incr eased after 32 wk of age (P<0.05). In summary, numerical pixel values comprising the ultrasound images of the developing testes, prostate an d vesicular glands revealed a complex development pattern that may ref lect important details of developmental stages. (C) 1997 by Elsevier S cience Inc.