تحلیل فنوتیپی و ژنوتیپی سن هنگام نخستین زایش درگاوهای شیری هلشتاین ایران

نوع مقاله : علمی پژوهشی- ژنتیک و اصلاح دام و طیور

نویسندگان

گروه علوم دامی، دانشکده کشاورزی، دانشگاه فردوسی مشه

چکیده

سن اولین زایش اثر مهمی روی سودآوری و مدیریت تولیدمثلی گله گاو شیری دارد، به طوری که زایش تلیسه ها در سن بیشتر از 24 ماهگی به دلیل از دست رفتن فرصت تولید شیر و کاهش روز های تولیدی زندگی دام، باعث افزایش هزینه های تولید در صنعت گاو شیری می شود. به منظور برآورد اجزای ژنتیکی و بررسی روند تغییرات سن اولین زایش گاوهای شیری هلشتاین در ایران از 19499 رکوردهای تولید و تولید مثل 96 گله گاوهای شیری هلشتاین طی سال های 1375 لغایت 1387 استفاده شد. داده ها با استفاده از یک مدل تک صفتی و نرم افزار Wombat آنالیز شد. وراثت پذیری صفت سن اولین زایش 0994/0 برآورد گردید. میانگین سن اولین زایش گاوهای شیری هلشتاین در ایران طی سال های 1375 لغایت 1387، 91/24 ماه برآورد شد که طی سال های مورد مطالعه به واسطه تلقیح و زایش زودتر تلیسه ها کاهش یافته است، به طوری که گاوهایی که در سال های 1375 و 1376 متولد شده اند بیشترین سن در اولین زایش را داشتند و گاوهایی که در سال های 1386 و 1387 متولد شده اند کمترین سن را در زمان اولین زایش نشان دادند. با توجه به مقادیر برآورد شده ارزش های اصلاحی صفت سن اولین زایش، روند ژنتیکی این صفت طی سال های تولد 1375 لغایت 1387 برآورد شد. بدین صورت که روند ژنتیکی در بعضی سال ها مثبت و برای بعضی سال های مورد مطالعه منفی برآورد شد و نشان می دهد که در راهبردهای انتخاب، کاهش ژنتیکی سن اولین زایش در گله های ایران مد نظر قرار نگرفته است، هرچند که از نظر فنوتیپی این صفت کاهش داشته است. گاوهای استان های یزد، مرکزی و خراسان جنوبی بیشترین سن و گاوهای استان های کرمانشاه، آذربایجان شرقی و اردبیل کمترین سن اولین زایش را داشتند. شرایط اقلیمی و آب و هوایی مناسب می تواند در افزایش باروری تلیسه ها و کاهش سن اولین زایش مؤثر باشد، هرچند عوامل مدیریتی، با وجود عوامل جوی مناسب در برخی از استان های کشور اثر به سزایی روی این صفت داشت.

کلیدواژه‌ها


عنوان مقاله [English]

Phenotypic and genotypic analysis of age at first calving in Iranian Holstein dairy cows

نویسندگان [English]

  • Atefeh Seyeddokht
  • Ali Asghar Aslami Nejad
  • Morteza Bitaraf Sani
Ferdowsi University of Mashhad
چکیده [English]

Introduction: Age at first calving (AFC) has an important effect on profitability and reproductive management of dairy cattle. Every month increase in AFC beyond 24 months increases the cost of production. The time between birth and first calving represents a period in which replacement heifers are not generating income. Instead this rearing period requires considerable capital expenditures including feed, housing, and veterinary expenses. These expenses constitute 15% to 20% of the total expenses related to milk production. A basic approach to reduce this cost is to decrease the time between birth and her first freshening. Worldwide recommendations for one particular AFC might be an incorrect management goal for all of the cattle on all of the farms, since the recommendation might not represent the management goals and/or capabilities of a particular production system or farm. We realize that each dairy has its own set of unique management and environmental conditions, which makes a universal AFC and BW after first calving, a difficult goal to achieve. The AFC has a profound influence on the total cost of raising dairy replacements in which older calving heifers are more expensive to raise than younger ones.

Materials and methods: A total of 19499 calving records belonged to 96 herd from 1996 to 2008 were used to estimate genetic components and genetic trend for age at first calving in Holstein dairy cows of Iran. Data were analyzed using a univariate model and Wombat software. Linear regression of estimated breeding values on calving year was used to estimate genetic trend.

Results and Discussion: Estimated genetic trend was positive for some years and was negative for others and showed that reducing age at first calving has not been considered in the selection strategies; however, the phenotypic trend was decreased. The age at first calving for Yazd, Markazi, and southern Khorasan provinces were the highest and for Kermanshah, East Azarbayjan, and Ardebil provinces were the lowest compared to the other provinces. Most analysis shows that the financial benefit afforded to heifers that freshen at a low AFC seems to at the least offset any milk lost in the first lactation. The NRC (2001) suggests a post weaning BW equal to 82% of her mature body weight. This can be attained with a maximal pre-pubertal ADG of 2.0 lbs/d if a traditional pre-weaning program is employed or 1.8 lbs/d if an intensified pre-weaning program is employed. Due to the well-defined link between insufficient BW at calving and increased mortality and disease in first calf heifers, attaining this aim post calving BW is of critical importance. Ettema and Santos (2004) conducted an economic analysis of the AFC study that was discussed above. Rearing prices for the medium and high AFC groups were $40.34 and $107.89, respectively, more than that of the low AFC collection. Income for each AFC collection was adjusted for the cost of rearing, assessed feed to increase milk yield, stillbirths, diseases, open days, culling, mortality, labor cost, and the value of milk and calf produced as well as the value of a cow at the end of the 310 day studies. Adjusted income was $119.73 and $9.08 more for the medium and high AFC, respectively, than for the low AFC. These values were not significantly diverse implying no single AFC had an economic benefit over another. Nevertheless, these authors (Ettema and Santos, 2004) did not study the net present value of money in their analysis as St-Pierre (2002) did. If this had been considered, it would presumably shift the economic improvement to the low AFC heifers.

Conclusion: Good climatic and weather conditions can be effective factors for reducing the age at first calving and cause to increase the fertility of heifers. However, management methods had a significant effect on this trait in some provinces. The primary benefits of reducing AFC include reducing rearing costs as well as reducing the amount of time in which the heifer is only a capital drain on farm resources. The primary disadvantage of reducing AFC is that it is frequently associated with a reduction in first lactation milk yield. Despite this reduction in first lactation milk yield, production per year of herd life is usually increased by reduced AFC. First lactation may be influenced by AFC, future lactations are definitely not. Furthermore, stay ability and health of cows is not influenced by reduced AFC as long as first calf heifers freshen at an adequate weight.

کلیدواژه‌ها [English]

  • Age at first calving
  • Dairy cattle
  • Genetic trend
  • Phenotypic trend
  • profitability
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.