Ansari- Lari, M., M. Rezagholi and M. Reiszadeh. 2009. Trends in calving age and calving intervals for Iranian Holstein in Fars province, Southern Iran. Tropical Animal Health Production, 41:1283-1288.
2. Biffani, S., Marusi, F., Biscarini, F. & Canavesi. F. 2005. Developing a genetic evaluation for fertility using angularity and milk yield as correlated traits. In: Proceedings of the 2005 INTERBULL Meeting, Uppsala, Sweden, June 2-4, Bulletin, 33, 63-66.
3. Castillo-Juarez, H., P.O., Oltenacu, R.W. Blake, C.E. Mcculloch and E.G. Cienfuegos-Rivas. 2000. Effect of herd environment on the genetic and phenotypic relationships among milk yield, conception rate and somatic cell score in Holstein cattle. Journal of Dairy Science, 83:807-814.
4. Chokani, A., M. Dadpasand, H. Mirzaei, M. Rokuei and M. B. Sayyadnezhad. 2009. An Estimation of Genetic Parameters for some Reproductive Traits and their Relationships to Milk Yield in Iranian Holstein Cattle. Iranian Journal of Animal Science, 40 (4): 53-61. (In Persian).
5. Connor, M. 2006. Trends in Age at First Calving and Calving Intervals .PENNASTATE. College of Agricultural Sciences. Dairy and Animal Science, http://www.das.psu.edu.
6. Dastanian, V., S. Khalajzadeh and M. B. Sayyadnezhad. 2011. Estimation the genetic and phenotypic parameters of milk yield and its correlation with age at first calving in Iranian Holstein Dairy Cows. 1st National Conference on New Concepts in Agriculture, Save, Azad University. (In Persian).
7. De Jong, G. 2005. Usage of predictors for Fertility in the genetic evaluation application in the Netherlands. In: Proceedings of the 2005 INTERBULL Meeting, Uppsala, Sweden, June 2-4, 2005, Bulletin No, 33: 69-73.
8. Faraji- Arough, H., Aslaminejad, A.A., Farhangfar, H.2011. Estimation of Genetic Parameters and Trends for Age at First Calving and Calving Interval in Iranian Holstein Cows. Journal of Research in Agricultural Science, 7 (1): 79-87.
9. Farhangfar H., H. Naeemipour. 2007. Estimation of Genetic and Phenotypic Parameters for Production and Reproduction Traits in Iranian Holsteins. JWSS - Isfahan University of Technology. 11 (1):431-441. (In Persian).
10. Ghazi Khani, A., M. Heidari and M. B. Sayyadnezhad. 2011. Effect of age at first calving and mother age on productive traits of Holstein cattle. Animal Science and Research Journal, 7: 41-51. (In Persian).
11. Ghiasi H., A. Pakdel, A. Nejati – Javaremi, H. Mehrabani – Yeganeh, M. Honarvar, O. Gonzalez- Recio, M. Jesus Carabano and R. Alenda. 2011. Genetic variance components for female fertility in Iranian Holstein cows. Livestock Science, 139(3): 277-280.
12. Gonza´lez-Recio, O., M. A. Pe´rez-Cabal and R. Alenda. 2004. Economic value of female fertility and its relationship with profit in Spanish dairy cattle, Journal of Dairy Science, 87: 3053–3061.
13. Hare, E., H.D. Norman and J.R. Wright. 2006. Trends in Calving Ages and Calving Intervals for Dairy Cattle Breeds in the United States. Journal of Dairy Science, 89:365-370.
14. Heersche, G. 2010. Age at First Calving is Important. Cooperative Extension Service. University of Kentucky, College of Agriculture.
15. Honarvar, M., M. Moradi Share Babak and S. R. Miraei Ashtiani. 2004. Estimation of Parameters for reproductive traits and their relationships with milk production in Iranian Holstein cows. Proceedings of the First Congress of Animal Sciences and Aquaculture, Tehran, 685-688. (In Persian).
16. Lucy, M.C. 2001. Reproductive loss in high-producing dairy cattle: Where will it end? Journal of Dairy Science, 84:1277-1293.
17. Makgahlela, M.L., C.B. Banga, D. Norris, K. Dzama and J.W. Ngambi. 2008. Genetic analysis of age at first calving and calving interval in South African Holstein cattle. Asian Journal of Animal and Veterinary Advance, 3(4): 197-205.
18. Marti, C.F. and D.A. Funk. 1994. Relationship between production and days open at different levels of herd production. Journal of Dairy Science, 77:1682-1690.
19. Meyer, K. 2007. WOMBAT -A program for mixed models analyses in quantitative genetics by restricted maximum likelihood (REML). Journal of Zhejiang University Science, B 8, 815–821.
20. Moore, R.K., B.W. Kennedy, L.R. Schaeffer and J.E. Moxley. 1990. Relationships between reproduction traits, age and body weight at calving and days dry in first lactation Ayrshire and Holsteins. Journal of Dairy Science, 73:835-842.
21. Nederlands Rundvee Syndicaat. 2005. Cooperatie Rundveeverbetering Delta, Arnhem, the Netherlands.
22. Nilforooshan, M.A. and M.A. Edriss. 2004. Effect of age at first calving on some productive and longevity traits in Iranian Holsteins of the Isfahan province. Journal of Dairy Science, 87:2130-2135.
23. Pirlo, G., F. Miglior, and M. Speroni. 2000. Effect of age at first calving on production traits and on difference between milk yield returns and rearing costs in Italian Holsteins Journal of Dairy Science, 83:603-608.
24. Plate-Church, A. 2002. Determining Optimal Age at First Calving. Communications Manager, Cooperative Resources International, National Animal Health Monitoring System.
25. VanRaden, P. M., Sanders, A.H., Tooker, M. E., Miller, R.H., Norman, H.D., Kuhn, M.T. and Wiggans, G. R. 2004. Development of a national genetic evaluation for cow fertility. Journal of Dairy Science, 87: 2285-2292.
26. Vergara O.D., M.A. Elzo and M.F Ceron Munoz. 2009. Genetic parameters and genetic trends for age at first calving and calving interval in an Angus-Blanco Orejinegro-Zebu multibreed cattle population in Colombia. Livestock Science, 126: 318–322.
27. Wall, E., S. Brotherstone, J. A. Woolliams, G. Banos, and M. P. Coffey, 2003. Evaluation of fertility using direct and correlated traits. Journal of Dairy Science, 86: 4093–4102.
28. Wasike C.B., D. Indetie, J.M.K. Ojango and A.K. Kahi. 2009. Direct and maternal (co)variance components and genetic parameters for growth and reproductive traits in the Boran cattle in Kenya. Tropical Animal Health Production, 41: 741–748.
29. Wilson, R. 2006. Age at First Calving: The Dollars and Sense. GENEX, Cooperative, Inc.