Phenotypic and Genetic Factors Affecting on Reproductive Lifetime of Lori-Bakhtiari Ewes
محورهای موضوعی : Camel
1 - Department of Animal Science, Chaharmahal va Bakhtiary Agricultural and Natural Resources Research and Education Center, AREEO, Shahrekord, Iran
کلید واژه: genetic parameters, reproductive efficiency, ewe's lifetime,
چکیده مقاله :
In this study phenotypic and genetic factors affecting the reproductive efficiency of Lori-Bakhtiari ewes were determined using 8202 reproductive records of 2478 ewes collected at Shooli research station in the southwestern part of Iran (Shahrekord) during 1989 to 2012. Reproductive efficiency over all consecutive lambing opportunities were calculated by adding the total reproductive efficiency traits per ewe joined for all of the parturition opportunities. Reproductive traits included in the current study were: number of parity (NP), total number of lambs born (TNLB), total number of lambs weaned (TNLW), total of lambs birth weight (TLBW), total of lambs weaning weight (TLWW), total of lambs weaning weight per kg ewe body weight (TLWW/EBW) and total of lambs weaning weight per kg metabolic ewe body weight (TLWW/MEBW). The data set analyzed with multi-trait animal model included the fixed effects of birth year of ewe, number of parturition in ewe's lifetime, ewe body weight as covariate and random effects direct additive genetic and residual. The overall mean of NP, TNLB, TNLW, TLBW, TLWW, TLWW/EBW and TLWW/MEBW were 3.31, 3.31, 3.21, 16.51 kg, 87.31 kg, 1.51 and 4.16, respectively. The effect of non-genetic factors were significant for all investigated traits in this study (P<0.01). The heritability estimates were medium (0.30) for NP and low (0.08 to 0.11) for other reproductive efficiency traits. The estimates of genetic and phenotypic correlations between the traits were high (0.72 to 0.99) or medium to high (0.57 to 0.99). Thus, improving environmental effects could make significant improvements in reproductive efficiency traits at first. The low to medium heritability estimate and high genetic correlations obtained between reproductive efficiency traits in ewe's lifetime and high phenotypic standard deviation from them indicated that improvement by selection of all of traits, especially NP can be improved TLWW as net reproductive efficiency trait in Lori-Bakhtiari ewes.
عوامل فنوتیپی و ژنتیکی مؤثر بر بازدهی تولید مثل در خلال طول عمر یک میش با استفاده از 8202 رکورد صفات تولید مثلی در طول عمر 2478 رأس میش جمعآوری شده طی سالهای 1989 تا 2012 مربوط به گله تحقیقاتی ایستگاه گوسفند لری بختیاری (شولی) واقع در جنوب غربی ایران (شهرکرد) برآورد گردید. بازدهی تولیدمثلی در خلال فرصتهای برهزایی، از حاصل جمع همه زایشها به ازای هر رأس میش در معرض آمیزش محاسبه شد. بازدهی تولید مثل شامل تعداد شکم زایش (NP)، تعداد کل برههای متولد شده (TNLB)، تعداد کل برههای شیرگیری شده (TNLW)، کل وزن تولد برهها (TLBW)، کل وزن شیرگیری برهها (TLWW)، کل وزن شیرگیری به ازای هر کیلوگرم وزن بدن میش (TLWW/EBW) و کل وزن شیرگیری به ازای هر کیلوگرم وزن متابولیکی میش (TLWW/MEBW) بودند. دادهها به وسیله مدل حیوانی چندصفتی شامل اثر عوامل ثابت سال تولد میش، تعداد زایمان در طول عمر میش، متغییر کمکی وزن بدن میش، و اثر عوامل تصادفی ژنتیکی افزایشی حیوان و باقیمانده تجزیه شدند. میانگین کل صفات مرتبط با بازدهی تولیدمثلی به ترتیب معادل 31/3، 31/3، 21/3، 51/16 کیلوگرم، 31/87 کیلوگرم، 51/1 و 16/4 بودند. انحراف استاندارد همه صفات مورد بررسی به خصوص برای صفت TLWW بالا بودند. اثر عوامل غیر ژنتیکی بر روی همه صفات مورد بررسی معنیدار بودند (01/0P<). برآوردهای وراثتپذیری متوسط (30/0) برای NP و پایین (08/0 تا 11/0) برای سایر صفات بودند. همبستگیهای ژنتیکی و فنوتیپی بین صفات بازدهی تولیدمثلی در طول عمر میش به ترتیب بالا (72/0 تا 99/0) و متوسط تا بالا ( 57/0 تا 99/0) برآورد شدند. بنابراین، بهبود عوامل محیطی در ابتدا میتواند بهبودی قابل ملاحظهای در همه صفات مرتبط با بازدهی تولیدمثلی ایجاد نماید. برآورد وراثتپذیری پایین تا متوسط و همبستگیهای ژنتیکی گرفته شده بین صفات تولیدمثلی در طول عمر میش و انحراف استاندارد فنوتیپی بالای آنها، نشان دهنده امکان بهبودی به وسیله انتخاب برای همه صفات میباشد، به خصوص انتخاب برای NP میتواند کل وزن شیرگیری به عنوان بازده خالص تولیدمثلی در میشهای لری بختیاری را افزایش دهد.
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