This study was conducted on 94 Frieswal (5/8 Holstein Friesian 3/8 Sahiwal) crossbred bulls of three different grades, categorized based on their semen freezability visualising Group 1 (consistently freezable semen producer bulls, N 5 11), Group 2 (inconsistent freezable, N 5 16) and Group 3 (Non freezable, N 5 67). Each group was further divided into two classes that is young (up to 30 months) and adult (31 to 70 months) bulls depending upon their age. Sperm morphology was studied by using the eosin-nigrosin staining technique. Bulls age significantly (P , 0.01) affected semen quality and sperm morphology. In adult bulls, semen volume, mass activity and sperm concentration were 36%, 17.56% and 19.6%, respectively, higher than young. Initial progressive motility (%) and livability showed significant (P , 0.01) improvement with the advancement of age (43.37 6 1.21 and 67.71 6 1.11, respectively, in young; 53.02 6 1.11 and 74.17 6 1.03, respectively, in adult). In young bulls, sperm head, mid piece, tail abnormality and total abnormal sperm percent (12.38 6 0.92, 4.87 6 0.24, 11.01 6 0.60 and 28.26 6 1.34, respectively) were 1.85, 1.27, 1.20 and 1.44 folds higher than that of their mature stage (6.69 6 0.64, 3.82 6 0.32, 9.14 6 0.64 and 19.66 6 1.31, respectively). Significant reduction (P , 0.01) in micro cephalic sperm, free heads, bent mid piece, looped mid piece and proximal protoplasmic droplets were observed at mature age as compared with their younger stage. In bulls of consistent freezing category, abnormal sperm heads significantly decreased from 4.40 6 0.31% to 3.28 6 0.02% on maturity. Similarly, in inconsistent freezing grade bulls sperm head abnormality (9.28 6 0.75% to 5.13 6 1.20%) and total abnormal sperm percent (24.89 6 1.43 to 18.73 6 3.40) was decreased over the age. On the contrary, in non-freezing category bulls' sperm morphology did not show significant (P . 0.05) improvement with age advancement, rather some abnormalities like long slender head, under developed/deformed head, abaxial implantation of mid piece, double mid piece, stump tail and distal protoplasmic droplets tend to increased significantly (P , 0.05) with age of bulls. Results indicated that in potential Frieswal bulls semen quality and sperm morphology were improved from young to mature stage, where as, in poor quality (non-freezing) semen producer bulls neither the morphology nor the semen quality showed any improvement with maturity. It was recommended that crossbred bulls producing more than 25% morphologically abnormal sperms in young age (below 30 months) along with poor progressive motility (,50%) and low sperm concentration (,1000 million/ml) need immediate culling with out any expectation of further improvement in semen quality with age advancement.Keywords: Sperm abnormality, Frieswal crossbred bull, Sperm morphology, Bos indicus 3 Bos taurus Implication Assessment of sperm morphology is one of the most important aspects for semen evaluation and successful fertilisation. High percentage of morphologically abnormal spe...

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Linear type traits are easily measurable phenotypic characteristics that help breed characterization, selection of animals for breeding and found to be associated with animals’ performance. Unlike cows, there have been limited studies linking body linear traits with male reproductive ability and semen cryo‐preservability of breeding bulls. Present study reported the age‐related changes in body linear type traits in Frieswal (N = 378) dairy bulls and its relevance with reproductive potentials of breeding bulls. Our results indicated that body frame size traits were significantly and positively correlated with gonadal linear traits. Among the selected body mophometric parameters body length, chest girth and head circumference were the important body linear type traits having capability to discriminate between bulls of frozen semen doses (FSD) and non‐FSD categories. Discriminant function has been developed based on body linear traits of crossbred dairy bulls to find out males of superior reproductive potentials. Our finding provided evidence that body length (humerous tuberosity to tuber ischii) was the most powerful linear body trait associated with breeding bulls’ reproductive ability and semen quality.

Mammalian circadian locomotor output cycles kaput (CLOCK) gene encodes a transcription factor that affects both the persistence and the period of circadian rhythms. Earlier reports suggested that CLOCK gene might be associated with male infertility in human. Present investigation, for the first time, reports that CLOCK gene expresses differentially between good and poor quality crossbred bull semen. The relative expression of CLOCK was significantly (p < 0.05) higher among good quality bull semen than motility-impaired ones. Clusterins (CLU) are series of genes associated with a variety of physiological activities including spermatogenesis, apoptosis and degenerative disease conditions. In the present context, we also investigated that the expression of CLU gene was significantly (p < 0.05) higher among motility-impaired crossbred bull semen compared to the good quality one.

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