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The present study was conducted with the objective of evaluating Cholistani service bulls on the basis of their postthaw sperm parameters and fertilizing potential through artificial insemination under the prevailing local climate. Semen from each experimental bull (n = 6) was collected at weekly intervals over a 12-month period, frozen, thawed, and evaluated for postthaw sperm parameters. Fertility rate of postthaw samples was determined by inseminating 1200 Cholistani cows in 2 trials: Trial 1 had 600 cows with 100 inseminations per bull to assess the effect of individual bulls and Trial 2 had 600 inseminations with 150 insemination doses frozen per season to assess effect of seasons. The results revealed a significant effect (P < 0.05) of bulls and seasons on all the postthaw semen parameters studied. The overall fertility rate recorded in the present study was 69.7% (837/1200), being 68.5% (411/600) and 71.0% (426/600) in the first and second trials, respectively. The highest fertility rate of 75.3% (113/600) was noticed in the hot dry summer and the lowest of 67.3% (101/600) in the hot wet summer (67.3%). However, differences in fertility rate within bulls and within seasons were statistically nonsignificant (P > 0.05).