Evaluation of Genetic Components and The Effect Of Non-Genetic Factors on Seminal Traits and Semen Rejection Rate in Murrah Buffalo Bulls Reared in Tropical Climatic Condition

Abstract

\n The present study was designed to determine the effect of genetic and non-genetic factors on semen production and semen discard patterns in Murrah buffalo bulls. Data on 54,268 ejaculates covering a period of 11 years were collected from 77 Murrah bulls maintained in the semen station. The effect of non-genetic factors on seminal parameters was analyzed using least-squares analysis of variance under general linear model. The repeatability estimates were computed by REML using WOMBAT program. Semen rejection rate among the main factors was evaluated using Chi-square test. The overall least-s quares means for semen volume, sperm concentration, total sperm per ejaculate, mass activity, initial motility, post-thaw motility, and frozen semen doses per ejaculate were 2.65 ml, 1222.04 million per ml, 3030.10 million, 2.64, 67.45%, 51.73%, and 128.80 doses. Similarly, repeatability estimates were 0.27, 0.25, 0.22, 0.28, 0.34, 0.27 and 0.23, respectively. The non-genetic factors, ejaculate number, period, season, and bull age, had a highly significant (P <0.01) effect on all the seminal traits. The bull-to-bull variation was also found to be significant (P <0.01). The phenotypic correlation coefficient between the traits was highly significant and positive for most traits. The semen rejection rate was high in pre-freezing (2.07%) than post-freezing (17.91%). Better seminal quality was observed in the first ejaculate, period V, south-west monsoon, and summer seasons. Bulls above eight years of age performed better than younger bulls, with best performance in bulls 12 years and above. The repeatability estimates were low to moderate, indicating a scope for selection based on moderate repeatable traits. This would be useful to the semen stations in tropical regions to frame suitable strategies to improve the quality and quantity of semen production.