Study of Factors Affecting Longevity and Survival of Iranian Guilan Sheep Using Linear and Non-Linear Models
محورهای موضوعی : Camel
م. نداف فهمیده
1
(Department of Animal Science, Faculty of Agricultural Science, University of Guilan, Rasht, Iran)
ن. قوی حسین زاده
2
(Department of Animal Science, Faculty of Agricultural Science, University of Guilan, Rasht, Iran)
م. گلشنی
3
(Agriculture Jihad Organization of Guilan, Rasht, Iran)
کلید واژه: lifetime, fat tailed sheep, culling, hazard ratio, non-genetic factors,
چکیده مقاله :
The objective of this study was to evaluate non-genetic factors affecting longevity and survival of Guilan sheep from birth to yearling. Longevity and survival records of 41037 lambs born from 496 rams and 10256 ewes of Guilan sheep were analyzed using linear and Weibull models. Results indicated that the overall mean of longevity was 1260.84 days. The fixed effects of flock, dam age, sex, year and month of birth and interaction between dam age-sex had significant effects on longevity (P<0.05). But birth type, birth weight and interactions of sex-birth type and dam age-birth type had no significant effect on longevity (P>0.05). Male lambs had lower survival and greater hazard ratio compared with female lambs. Lambs which born in recent years and last months of year had greater hazard ratios and lower survival in the period from birth to 2-months and birth to yearling. Lambs which born in early months of year had greater survival and lower hazard ratio than those birth to 3, 6 and 9 months of age. Although twin lambs had lower survival and greater hazard from birth to 2 and 3 months of age periods, difference of single and twin lambs was not significant in other time periods. In conclusion, linear and non-linear models can be used to study the survival of lambs and it’s possible to improve this important item through modifying non-genetic factors.
زنده­مانی بره­ها یکی از مهم­ترین فاکتورهای مؤثر بر سودآوری گله­های گوسفند می­باشد. هدف از این تحقیق بررسی عوامل غیرژنتیکی مؤثر بر زنده­مانی گوسفندان گیلان از تولد تا یک­­سالگی با استفاده از مدل­های خطی و غیرخطی می­باشد. رکوردهای طول عمر و زنده­مانی تعداد 41037 راس بره، حاصل از 496 رأس قوچ و 10256 رأس میش، گوسفندان گیلان، با استفاده از مدل­های خطی و نسبت خطر با تابع ویبول تجزیه شدند. نتایج نشان داد که میانگین کل طول عمر از تولد تا یک­سالگی برابر با 84/1260 روز بود. اثرات ثابت گله، سن مادر زمان زایش، جنسیت، سال و ماه تولد و اثر متقابل سن مادر زمان زایش-جنسیت ارتباط معنی­داری با طول عمر داشتند (05/0>P). اما اثرات نوع تولد، وزن تولد، اثرات­ متقابل جنسیت- نوع تولد بره، سن مادر زمان زایش-نوع تولد بره، ارتباط معنی­داری با طول عمر نداشتند (05/0<P). بره­های نر میزان زنده­مانی کمتر و نسبت خطر بیشتری در مقایسه با بره­های ماده داشتند. بره­های متولد شده در سال­های اخیر و ماه­های آخر سال با نسبت خطر بیشتر و زنده­مانی کمتر در دوره سنی تولد تا 2 ماهگی و تولد تا یک­سالگی قرار داشتند. بره­های متولد شده در ماه­های ابتدایی زایش زنده­مانی بیشتر و نسبت خطر کمتری داشتند که در سن 3، 6 و 9 ماهگی قرار داشتند. با وجود اینکه در دوره­های سنی تولد تا 2 و 3 ماهگی، بره­های دو قلو زنده­مانی کمتر و نسبت خطر بیشتری از بره­های تک ­قلو داشتند، در سایر سنین تفاوت بین بره­های تک­قلو و دو­قلو معنی­دار نبود. به منظور بررسی زنده­مانی بره­ها، مدل­های خطی و غیر خطی می­توانند مورد استفاده قرار گیرند و با مدیریت عوامل غیر ژنتیکی، بهبود این امر مهم ممکن شود.
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