Relationship of age to body weight, scrotal circumference, testicular ultrasonograms, and semen quality in Sahiwal bulls

Abstract

The objective of the present study was to determine the relationship of age to body weight (BW), scrotal circumference (SC), number of pixels of testicular ultrasonograms (NP), and semen quality in Sahiwal bulls. The study was based on 128 Sahiwal bulls of different age groups (from 0 to >100 months of age). Bulls were evaluated for SC, BW, and NP. Semen was evaluated once a week for five consecutive weeks from regularly collected donor bulls (n = 86) ranging in age from 25-30 to >100 months. Ejaculate volume, sperm motility, sperm concentration, sperm morphology, percent live sperms, sperm plasma membrane integrity, and normal acrosome were compared among different age groups. Mean SC and BW increased (P < 0.05) in a curvilinear manner from birth to >100 months of age. Mean NP of testicular ultrasonograms increased (P < 0.05) from 0 to 24 months and then plateaued until >100 months of age. Body weight, SC, and NP were positively correlated with age from birth until >100 months (r = 0.91, 0.87, and 0.40, respectively). Ejaculate volume (5.7 ± 0.2 vs. 4.6 ± 0.09 ml) and sperm concentration (1,281.6 ± 17.7 vs. 1,115.8 ± 55.9 × 10(6)/ml) increased (P < 0.05) in mature bulls compared to younger ones. However, motility (68.6 ± 0.3%), plasma membrane integrity (50.8 ± 1.0%), and normal acrosome (74.8 ± 0.5%) remained insignificant due to age. In six of eight age groups studied, morphological abnormalities were well within the range (18.1 ± 0.3%). In conclusion, the BW, SC, and NP of testicular ultrasonograms, ejaculate volume, and concentration increased with age. Moreover, semen quality is fairly independent of age except volume and concentration in Sahiwal bulls.

Associations between feed efficiency, sexual maturity and fertility-related measures in young beef bulls

“…Interestingly, the minimum pixel intensity found here was also correlated with age at collection, indicating that older bulls, likely closer to the onset of puberty or sexual maturity, have higher pixel intensity values, which is also shown elsewhere (Ahmad et al, 2011;Brito et al, 2012). In addition, a larger scrotal circumference was associated with a lower occurrence of immature seminiferous tubules and a lower incidence of distal droplets in sperm.…”

“…Ultrasound assessment of testes Ultrasonography of the testes was carried out with the same ultrasound scanner described above and connected to a 5 MHz linear array transducer (Ahmad et al, 2011;Brito et al, 2012). Standardized ultrasound settings (focus of 1 and 2; overall gains of 90; near gain of 25; far gain of 2.1) were used for all animals.…”

“…For example, IR thermography is used to evaluate thermal patterns of the scrotum that are related to bull fertility (Coulter, 1988); recent studies suggest semen production and quality are influenced by scrotal temperature (Kastelic, 2014). Testicular ultrasonography is used to assess testicular echogenicity and respective image pixel intensity (Ahmad et al, 2011), which is directly associated with sexual maturity (Evans et al, 1996).…”

Relationship between body and testicular measurements in young buffalo bulls in Cuba

“…Body weight mean increases more rapidly between 0 and 36 than between 37 and 100 months of age (Ahmad et al, 2011) and there is a close relationship with testicular development (Cardoso da Luz et al, 2013). During this period sperm cell division begins at approximately 12 months of age and spermatogenesis starts at 15 months of age (Arrighi et al, 2010).…”

“…In case of relatively close R 2 values, the mean squared error is used to select the model that best expresses the fit of the studied variables since it penalizes larger deviations (Draper and Smith, 1998). It should be noted that several reports used only r or R 2 , and significance level for model comparison (Bongso et al, 1984;Yanez et al, 1997;Cruz et al, 2001;Vásquez and Arango, 2002;Sing et al, 2010;Ahmad et al, 2011;Cardoso da Luz et al, 2013;Henry et al, 2013).…”