Effect of inbreeding on preweaning growth traits and survival rate in Sakiz sheep.

ABSTRACT The objective of this study was to estimate the effect of inbreeding on birth weight (BW), weaning weight (WW90), andlamb survival rate (LSR) in Sak1z sheep. The effect of inbreeding on BW, WW90, and LSR traits was studied byanalysis of variance technique and regression method. Inbreeding had a significant effect on BW and the regressioncoefficient of inbreeding on BW was -0.0245–0.0076 kg (P<0.01). The mean level of inbreeding (F) of all animalsoverall years was 2.25% for lambs. The inbred lambs rate was 17.7%. The coefficient of inbreeding ranged from 6.25%to 25.0% and average was 12.68% for birth weight in inbred lambs. Inbreeding weren ˇt a significant effect on weaningweight at 90 days of age and lamb survival rate. It was concluded that inbreeding showed deleterious effects on birthweight and had a no effect on lamb ˇs weaning weight and survival rate.Key words: Inbreeding, Sak1zsheep, Preweaning growth, Lamb survival INTRODUCTION Sak1z sheep is one of the most important Turkishbreed of sheep famous for high milk production andprolificacy. The home tract of this breed includes Aegeanregion surrounding Izmir in Turkiye. Approximately 50-60 thousand heads of Sak1z sheep are present in thecountry (Kaymakc1, 2006).Any genetic improvement programs applied forlivestock are based on two main approaches: selectionand breeding systems. Intensive selection within a singlepopulation reduces the genetic variability and increasesthe rate of inbreeding as compared to crossbreeding. Theinbreeding is thought to be a useful tool to improve thesheep population by increasing the frequency of desirablegenes, but also leads to economic losses. The inbreedinglevel is considerably influenced by the ratio of males tofemales, reproduction ability, mating system, andpopulation size (Norberg and Sorensen, 2007, Barczak etal., 2009). Inbreeding is the mating of related individuals,and results in some loci bearing alleles that are identical-by-descent. Identity by descent occurs because allelesfrom one common ancestor may flow through multipleoffspring (Michelle, 2003).The objective of this study is to determine theeffect of inbreeding on birth, weaning weight and lambsurvival rate on Sak1z lambs.

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