Abstract
Abstract. The present study aims to investigate the age-related changes in testicular parameters and their association with plasma triiodothyronine (T3), thyroxine (T4), and testosterone in male Murrah buffaloes. Testicular measurements and single blood samples were collected from male Murrah buffaloes (n= 103) aged between 6 months and 8 years. The correlation coefficients of average testicular length (ATL), paired testis width (PTW), and scrotal circumference (SC) in relation to age were 0.88, 0.91, and 0.90, respectively. The regression equation between testicular weight (TW) and age was Y=1.48×x0.005 (r= 0.90; R2= 0.79). Plasma T4 and testosterone increased significantly (p< 0.001) with age and their levels ranged between 12.9 and 41.8 and 0.05 and 1.48 ng mL−1, respectively. With respect to associations between testicular parameters and plasma hormone levels, we observed significant (p< 0.01) correlations between ATL, PTW, SC, TW, and plasma T4. A significant correlation (r= 0.31; p< 0.01) between plasma T4 and testosterone levels was also observed. However, the correlations between plasma T3 and testicular parameters and plasma T3 and testosterone were non-significant. From the present study, we conclude that plasma T4 is positively correlated with testicular parameters and plasma testosterone, indicating its role in testis development and steroidogenesis.
Highlights
Bull fertility is an important aspect because one bull may serve around 20 females under natural conditions or hundreds of thousands under an artificial insemination program (Devkota et al, 2011)
Reliable fertility information can be obtained on several bulls by using them to impregnate a large number of cows or by evaluating their semen quality
Testicular weight could be derived by indirect measurements such as testicular length and width and scrotal circumference (Bailey et al, 1998)
Summary
Bull fertility is an important aspect because one bull may serve around 20 females under natural conditions or hundreds of thousands under an artificial insemination program (Devkota et al, 2011). Reliable fertility information can be obtained on several bulls by using them to impregnate a large number of cows or by evaluating their semen quality These assessments are time consuming and require the necessary equipment and skills. The literature indicates the involvement of thyroid hormones in the development of testis and the production of testosterone, very few in vivo studies have been conducted to determine their association. With this perspective, the present study was designed to investigate the developmental changes in testicular parameter and its association with thyroid hormones and testosterone in male Murrah buffaloes.
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