بررسی عوامل مؤثر بر مرگ و میر بره‌های لری بختیاری از بدو تولد تا هنگام از شیرگیری

نویسنده

عضو هیات علمی مرکز تحقیقات کشاورزی و منابع طبیعی شهرکرد

چکیده

هدف از انجام این تحقیق شناسایی عوامل مهم و میزان تأثیر آنها در مرگ و میر بره های لری بختیاری از بدو تولد تا هنگام از شیرگیری بود. داده های مربوط به 4991 رأس بره متولد شده از سال 1370 تا 1384 در ایستگاه پرورش و اصلاح نژاد گوسفند لری بختیاری، مورد آنالیز آماری قرار گرفت. جهت آنالیز داده ها از مدل رگرسیون لجستیک استفاده شد که در آن متغیر مرگ به عنوان متغیر وابسته و متغیرهای وزن مادر در هنگام جفت گیری، سن مادر، وزن بره هنگام تولد، جنس بره، سال تولد بره و دهه تولد بره به عنوان متغیرهای مستقل وارد مدل شدند. علاوه بر ضرایب رگرسیون، نسبت های احتمال وقوع برای هر یک از متغیرهای پیوسته و هر یک از سطوح هر متغیر ناپیوسته نسبت به سطح اول آن متغیر محاسبه گردید. بر اساس نتایج حاصل، سال تولد بره، دهه تولد بره و وزن بره هنگام تولد اثر بسیار معنی داری بر مرگ ومیر بره ها داشتند. احتمال مرگ بره های تولد یافته در اوایل فصل زایش کمتر از احتمال مرگ بره های تولد یافته در انتهای فصل زایش و بره های تولد یافته در اوایل بهار بود. احتمال مرگ بره های نر 5/1 برابر احتمال مرگ بره های ماده بود. همچنین احتمال مرگ بره های متولد شده از میش های 5 ساله، کمتر از احتمال مرگ بره های حاصل از سایر میش ها بود. افزایش هر واحد به وزن تولد بره ها، باعث کاهش احتمال مرگ آنها از بدو تولد تا هنگام از شیرگیری می گردد اما افزایش یک واحد به وزن مادر در زمان جفت گیری، سبب افزایش جزئی در احتمال مرگ بره های آنها از بدو تولد تا هنگام از شیرگیری می شود.

عنوان مقاله [English]

Investigation of factors which affect lori-Bakhtiari lambs mortality from birth to weaning

نویسنده [English]

  • M Bagheri
Member of Scientific Board of Natural Resources and Agricultural Research Center of Shahrekord
چکیده [English]

The aim of this study was identification of important factors and their effects on mortality of Lori-Bakhtiari lambs from birth to weaning. The data set used for statistical analysis were collected from 4991 lambs born between 1370 and 1384 in flock at Lori-Bakhtiari sheep breeding station. Data was modeled using logistic regression. Mortality variable as dependent and ewe weight at mating, ewe age, lamb birth weight, lamb sex, year of birth and decade of birth as independent variables interred to the model. Odds ratios in addition to regression coefficients were derived for continued variables and each level of non-continued variable with respect to first level of that variable. According to results, year of birth, decade of birth and birth weight had very significant effects on lamb mortality. Mortality probability of lambs born in the initial month of parturition period was lower than mortality likelihood of lambs born in the end month of parturition and spring born lambs. Male lambs’ mortality likelihood was 1.5 times higher than mortality likelihood of female lambs. Furthermore, mortality likelihood of lambs of 5-year-old ewes was lower than mortality likelihood of lambs born in younger and older ewes. Mortality probability from birth to weaning decreased due to each unit increase in lamb birth weight but by each unit increase in ewe weight at mating, mortality rate of lambs partially increase.

1- Dorrance, M. J., and Roy. L.D. (1976) Predation losses of domestic sheep in Alberta. J. Range Manage. 29: 457.##

2- Festa-Bianchet, M. (1988) Age-specific reproduction of bighorn ewes in Alberta, Canada. J. Mammal. 69: 157.##

3- Fogarty, M.M., Dickerson, G.E. Young. L.D. (1985) Lamb production and its components in pure breeds and composite lines. III. Genetic parameters. J. Anim. Sci. 60: 40-57.##

4- Green, L.E., and Morgan. K.L. (1993) Mortality in early born, housed lambs in south-west England. Prev. Vet. Med. 17: 251-261.##

5- Guinness, F.E., Clutton-Brock, T.H. and Albon. S.D. (1978)Factors affecting calf mortality in red dear (Cervus elaphus). J. Anim. Ecol. 47: 817.##

6- Henne, D.R. (1980) Domestic sheep mortality on the Western  Montana ranch. In: R. L. Philips and C. J. Jonkel (Ed.) Proceedings of the 1975 predator symposium. P 133. University of Montana, Missoula.##

7- Hewson, R., and Verkaik. A.J. (1981) Body condition and ranging behavior of blackface hill sheep in relation to lamb survival. J. Appl. Ecol. 18: 401.##

8- Hosmer, D.W., and Lemeshow. S. (1989) Applied logistic regression. John Wiley and sons, New York.##

9- Johnston, W.S., Maclachlan, G.K. Murray. J.S. (1980) A survey of sheep losses and their causes on commercial farms in the north of Scotland. Vet. Rec. 106: 238.##

10- Large, R.J. (1970) The biological efficiency of meat production in sheep. Anim. Prod. 12: 393-401.##

11- Mandal, A., Prasad, H. Kumar, A. Roy, R. Sharma. N. (2007) Factors associated with lamb Mortalities in Muzaffarnagari sheep. Small Rumin. Res. 71: 273-279.##

12- Morris, C.A., Hickey, S.M. Clarke. J.N. (2000) Genetic and environmental factors affecting lamb survival at birth and through to weaning. N. Z. J. Agric. Res. 43: 515-524.##

13- Muskasa-Mugerwa, E., Lahlou-Kassi,A. Anindo, D.O. Rege, J.E. Tembley, S. Tobbo, M. Baker. R.L. (2000) Between and within breed variation in lamb survival and the risk factors associated with major causes of mortality in indigenous Horro and Menze sheep in Ethiopia. Small Rumin. Res. 37: 1-12.##

14- Mystrud, I., and Warren. J.T. (1991) Mortality transmitters-New instrument for animal loss research on Norwegian sheep ranges. Acta. Vet. Scand. 32:415.##

15- Nash, M.L., Hungerford, L.L. Nash,T.G. Zinn G.M. (1996) Risk factors for prenatal and postnatal mortality in lambs. Vet. Rec. 139: 64-67.##

16- Nass, R.D., Lynch, G. Theade J. (1984) Circumstances associated with predation rates on sheep and goats. J. Range Manage. 37:423.##

17- Peterson, C.J., and Danell O. (1985) Factors influencing survival in four Swedish sheep breeds. Acta. Agric. Scand. 35:217.##

18- Purser, A.F., and Young G.B. (1959) Lamb survival in hill flocks. Anim. Prod. 1:85.##

19- Purser, A.F., and Young G.B. (1964) Mortality among twins and single lambs. Anim. Prod. 6:321.##

20- Sawalha, R.M., Conington, J. Brotherstone, S. Villanueva B.  (2007) Analysis of lamb survival of Scottish Blackface sheep. Anim. 1: 151-157.##

21- Scrivner, J.H., Howard, w.E. Murphy a.H. and Hays J.R.  (1985) Sheep losses to predators on a California range, 1973-1983. J. Range Manage. 38: 421.##

22- Smith, G.M. (1977) Factors affecting birth weight, dystocia and preweaning survival in sheep. J. Anim. Sci. 44: 745-753.##

23- Wang, C.T., and Dickerson G.E. (1991) Simulation of life-cycle efficiency of lamb and wool production for genetic levels of component traits and alternative management options. J. Anim. Sci. 69: 4324-4337.##

24- Warren, J.T., and MystrudeI. (1995) Mortality of domestic sheep in free-ranging flocks in Southeastern Norway. J. Anim. Sci. 73: 1012-1018.##

25- Yapi, C.V., Boylan, W.J. Robinson R.A. (1990) Factors associated with causes of preweaning lamb mortality. Prev. Vet. Med. 10: 145-152.##