PhD

With the object of suggesting suitable measures in the selection of breeding bulls the structural and functional changes in testis and epididymis of 153 crossbreed males of different crosses viz., Jersey (CBJ), Brown Swiss (CBBS) and Holstein Friesian (CBHF) were investigated during the period from 1993 to 1998. The records maintained at Dhoni farm for the past five years were also screened to assess the incidence of various infertility conditions and the rate of culling. The study was carried out by dividing the males into three age groups viz., birth to 12 months (Group 1), 12 months to 24 months (Group II) and 24 months and above (Group III).
Group I-Bull calves
Measurement of testis and epididymis showed variation between different crosses. The mean scrotal circumference 19.42 ± 1.03 cm was found varied between different crosses. One case of bilateral cryptorchidism was detected. Among 53 bull calves 6 (11.32 per cent) were culled due to various reproductive disorders.
Group II-Growing bulls
Although different types of scroti were detected oval shape was predominant. The scrotal circumference was found to be 29.86 ± 0.38 cm. Lack of libido was predominant among growing bulls. The mean ejaculate volume, initial motility, sperm concentration and live sperm count were found to be 2.91 ± 0.16 ml, 49.77 ± 2.12 per cent, 1299.73 ± 56.25 million per ml and 58.76 ± 2.15 per cent respectively. Freezability of semen was highly correlated with volume and initial motility. Unilateral hypoplasia (4.48 per cent) and bilateral partial hypoplasia (8.96 per cent) were the main pathological conditions detected. Testicular degeneration was found to be in the extent of 16.41 per cent. One case of epididymal dysfunction was also detected. The rate of culling among growing bull was 47.58 per cent due to reproductive disorders.
Group III-Adult bulls
Although different shapes of scrotum were detected, oval shape was predominant. The scrotal circumference was 35.29 ± 0.74 cm. The prefreezing, post-freezing and total rejection were 12.00, 11.20 and 23.20 per cent respectively. The main infertility conditions noted were bilateral partial hypoplasia (5 per cent) and testicular degeneration (15 per cent). Estimation of seminal plasma enzymes revealed that those having 50 per cent and above freezability had lower level of seminal enzymes than those showing less than 50 per cent freezability. The percentage of adult bulls culled due to various reproductive disorders were 22.50 per cent. Thus it could be concluded that screening of bulls for better breeding performance should be started from birth onwards. Measurement of testis and epididymis and scrotal circumference give good indication for future breeding performance. Incidence of cryptorchidism should be guarded. Shape of scrotum has negligible importance. Lack of libido in growing bulls should not be neglected. Incidence of testicular hypoplasia and testicular degeneration needs special attention. Estimation of seminal plasma enzymes is a good indication for the suitability of semen for freezing.
Samples of tissues from testis affected with cryptorchidism, hypoplasia and degeneration were subjected to scanning electron microscopy.