Sperm motility is the prime functional attribute for semen quality and fertility of the bull. However, the bull's age directly affects the semen quality, and the bull's fertility and productive life decline with age. Even though research on age has been conducted in the past, it is still unclear how old a bull should be maintained at artificial insemination centers. The minimum standard protocol (MSP) states that a bull has an 8-years productive lifespan, yet it has been shown that some bulls older than 8 years have produced freezable ejaculates. It has yet to be established what the bull's ideal productive life is under the tropical climate of India without affecting in-vitro sperm functions. For the validation of the maximum age of a bull up to that it could be utilized in the artificial insemination centers, cut-off values of oxidative stress in freezable semen ejaculates were used. The current study was done at the Artificial Breeding Research Centre, ICAR-NDRI, Karnal, Haryana, India. A total of eighteen Sahiwal breeding bulls were divided into three groups: Young (2-4 years), Adult (> 4-8 years), and Older (> 8-11 years). Three ejaculates were taken from each bull; thus, a total of 18 ejaculates were utilized in each group for semen examination. Semen quality of Young bulls was poor compared with adult and older bulls. Seminal parameters such as dead, moribund, apoptotic, reacted acrosome, and protamine deficient sperms were higher in older bulls than in adult bulls; however, the values were non-significant. Less difference was found in the semen parameters among adult and older bulls. This indicates that the semen quality of older Sahiwal bulls was optimum, freezable, and can be utilized for up to 11 years (Average 9.5 years).
Keywords: Bull’s age; Oxidative stress; Productive life; Sperm motility.
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