PSX-5 Reproductive organ weights, morphology and sperm reserves in intact and short scrotum post-pubertal male dairy sheep lambs

Abstract

Abstract This study evaluated the use of short-scrotum castration to create sterile ram lambs. East Friesian x Lacaune male lambs born in February on a commercial sheep dairy were left intact (n = 19; IN) or rendered short-scrotum (n = 17; SS) within 10 d of birth. At 3 mo of age lambs were transferred to the study site and grazed as one group, while being supplemented with a grain mixture at 0.7 kg/d. Lambs were harvested at 6 mo of age, and reproductive tract of 5 IN and 5 SS lambs collected at random and shipped cold overnight for processing. Testis and epididymis were weighed. Segments of the left testis and epididymis were processed for histology, while a subsample of testicular parenchyma and epididymal segments of the right side were used to determine sperm reserves by tissue homogenization. Differences between testis types were determined using GLM of SAS. Testes and epididymal weights were reduced (P < 0.001) in SS (115 and 22 g) compared to IN (364 and 50 g) lambs. Seminiferous tubule diameter was also smaller (P < 0.001) in SS (142 µm) than IN (234 µm) lambs. Daily sperm production per gram testicular parenchyma (DSPG) was not different between types (3.8 vs. 2.3 million sperm/g; P = 0.06), but total daily sperm production was lower (P < 0.01) in SS (0.23 billion) than IN (1.34 billion) ram lambs. Considerable variation was noted in DSPG in IN lambs suggesting still incomplete development at this age, and accounting for the lack of a significant difference. Epididymal sperm reserves were markedly reduced (P < 0.001) in SS (0.1 billion) compared to IN (10.5 billion), and decreased along the epididymis, supported by evidence of phagocytic action by the epididymal epithelium. Data suggest that ram lambs rendered short-scrotum shortly after birth develop smaller testes with reduced sperm production, making them effectively infertile.