Genetic analysis of semen characteristic traits in Norwegian Red bulls at the artificial insemination center

摘要

Compared with cow fertility, genetic analyses of bullfertility are limited and based on relatively few animals.The aim of the present study was to estimate geneticparameters for semen characteristics of Norwegian Redbulls at the artificial insemination (AI) center (GenoAI station, Stange, Norway) and to estimate geneticcorrelations between some of these traits and andrologytraits measured at the performance test station.The data from the AI center consisted of records from137,919 semen collections from 3,145 bulls with informationon semen weight, sperm concentration, motilitybefore and after cryopreservation, motility change duringcryopreservation, and number of accepted strawsmade. Data from the performance test station included12,522 observations from 3,219 bulls on semen volume,concentration, and motility (%) when fresh and afterstoring for 24 and 48 h. Genetic parameters were estimatedusing linear animal repeatability models thatincluded fixed effects of year-month of observation, ageof bull, interaction between semen collection number,and interval between collections for all traits and typeof diluter for postcryopreservation traits. The randomeffects included test-day, permanent environmental,and additive genetic effects of the bull. Based on recordsfrom the AI center, we found that semen weight,sperm concentration, and number of straws were moderatelyheritable (0.18–0.20), whereas motility had alower heritability (0.02–0.08). Heritability of motility(%) was higher after cryopreservation than before.Genetic correlations among the semen characteristicsranged from unfavorable (−0.35) to favorable (0.93),with standard errors ranging from 0.02 to 0.22. Amongthe most precise genetic correlation estimates, numberof straws made from a batch correlated favorably withsemen weight (0.62 ± 0.06) and sperm concentration(0.44 ± 0.08), whereas sperm concentration was negativelycorrelated with weight (−0.33 ± 0.09). The geneticcorrelation between motility (%) before and aftercryopreservation was 0.64 ± 0.14, and motility changeduring cryopreservation had a strong favorable geneticcorrelation with motility after cryopreservation (−0.93± 0.02). The estimated genetic correlation (standarderror) between the traits volume, concentration, andmotility when fresh measured at the performance teststation and their respective corresponding traits at theAI center were 0.83 (0.05), 0.78 (0.09), and 0.49 (0.31).The final product at the AI center (number of acceptedstraws) correlated genetically favorably with all semencharacteristic traits recorded at the performance teststation (ranging from 0.51 to 0.67). Our results showthat the andrology testing done at the performance teststation is a resource to identify the genetically bestbulls for AI production.