Testicular development, histology, and hormone profiles in three yearling angus bulls with spermatogenic arrest

This article discusses the interactions between testis criteria and hormone profiles in Angus bulls with spermatogenic arrest. From 2 to 12 months (mo ), testis diameter and hormone concentrations (basal and GnRH-stimulated) w ere evaluated in 27 bulls. At 12 mo, testes were excised. The z statistical test was used to determine whether parameters in three infertile bulls wer e different (P < 0.05) from those in 24 bulls with normal spermatogenesis. Bull 1 had Sertoli cell-only syndrome and Bull 2 had 90% of the tubules wit hout germ cells and only Al spermatogonia in the remaining. In Bull 3, germ cells did not advance beyond the primary spermatocyte stage. At 12 mo, tes tes of Bull 1 (99 g), Bull 2 (105 g) and Bull 3 (32 g) weighed less than th ose of normal bulls (251.5 +/- 56 g). Sertoli cell numbers/testis in Bull 1 (3.8 x 10(9)) and Bull 2 (4.3 x 10(9)) were not different from those in no rmal bulls (4.9 +/- 0.3 x 10(9)), but were reduced in Bull 3 (1.6 x 10(9)). The number of Leydig cells per grant of testis parenchyma was higher in Bu ll 1 (5.4 x 10(7)), Bull 2 (7.3 x 10(7)) and Bull 3 (19 x 10(7)) than in no rmal bulls (3.6 +/- 0.2 x 10(7)). In Bulls 1 and 2, basal and GnRH-stimulat ed LH, FSH, testosterone (T), androstenedione (<Delta>(4)A) and estradiol 1 7-beta (E-2) were within normal ranges at most ages. However, basal FSH and LH were greater in Bull 3 than in normal bulls, probably the causes for hi gher Leydig cell density. Also in the same animal, GnRH induced lower respo nses in LH and FSH, consequence of low basal T and E-2 at some ages. Basal and GnRH-stimulated Delta (4)A in Bull 3 were greater than in normal bulls after 6 mo, indicating impairment of Leydig cell differentiation Deficiency in hormone secretion did not appear to be the cause of infertility, which paints toward impaired gonadal responses or secretion of intratesticular fa ctors, or genetic defects. Moreover, infertile animals may not always show pronounced changes in hormone secretion, but evaluation oft,tis growth arou nd puberty can help identify those animals that do not have proper gonadal development. (C) 2001 by Elsevier Science Inc.