title: Seasonal variations in serum levels of thyroid hormones and their relation with seminal quality and libido in buffalo bulls.
abstract: Blood samples from 15 Murrah buffalo bulls, (10- to 15- years-old) were collected during the summer, monsoon and winter seasons. The serum samples were analysed for thyroxine (T4) and triiodothyronine (T3) by RIA. Semen samples from these bulls were evaluated for various attributes. Sexual behaviour of these bulls was also recorded during the different seasons and was expressed as reaction time and refusal response. T4, T3, (T4 + T3) level and T4:T3 ratio did not reveal significant difference between seasons. Similarly, seminal characteristics did not exhibit any seasonal variation except for the percentage of live spermatozoa. However, the refusal response (no interest in mounting and ejaculating) was highest during summer months. T4 was significantly correlated to T(3) (r=0.53). Overall, T4 showed a positive correlation with seminal volume and initial motility while T3 exhibited a positive correlation with total sperm concentration and percentage of live spermatozoa. T3 was negatively correlated with refusal response only during the monsoon season. Correlation with other seminal and behavioural characteristics were not significant. The results indicated that although the sexual interest of buffalo bulls is reduced during the summer, the bulls can produce semen throughout the year under appropriate feeding and management conditions.
authors.affiliation: Department of Veterinary Physiology, Haryana Agricultural University, Hissar-125004 India.
authors.forename: N K
authors.initials: NK
authors.lastname: Dixit
authors.forename: S P
authors.initials: SP
authors.lastname: Agarwal
authors.forename: V K
authors.initials: VK
authors.lastname: Agarwal
authors.forename: P K
authors.initials: PK
authors.lastname: Dwaraknath