• Proceedings of the National Institute of Ecology of the Republic of Korea
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• 제2권2호
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• pp.108-113
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• 2021

Detrimental effects of inbreeding have been studied by many researchers for a long time. However, only a few studies have shown the occurrence of inbreeding depression due to evolutionary changes as a purging process. In this study, two different populations (inbreeding and outbreeding) of Drosophila melanogaster were compared to assess inbreeding effects on artificial population bottlenecks. For inbreeding conditions, a couple of D. melanogaster (one virgin and one male) were selected from an inbred population and cultured in a vial. For outbreeding conditions, a couple of D. melanogaster were selected from different populations and cultured in a vial. There were significant differences in body lengths of adults, but not in other parameters such as the total number of adults, the rate of survival, and the rate of wing mutants. The mean body length of adults of outbreeding populations was longer than that of inbreeding populations in the first generation (G1; P = 0.004), but not in the second generation (G2; P = 0.066). Although the other three parameters (total number of adults, rate of survival, and rate of wing mutants) showed differences in their mean values between inbreeding and outbreeding populations, these differences were not statistically significant. This might be due to genetic purging. This study demonstrated one additional experimental case related to inbreeding depression in artificial bottlenecked populations. Further studies are necessary to confirm the clear interaction between inbreeding depression and genetic purging using more generations and replicates (or samples) of D. melanogaster.

• Asian-Australasian Journal of Animal Sciences
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• 제10권5호
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• pp.510-513
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• 1997

This study examined the effects of ignoring inbreeding depression on (co)variance components for weaning weight through the use of Monte Carlo simulation. Weaning weight is of particular interest as a trait for which additive direct and maternal genetic components exist and there then is the potential for a direct-maternal genetic covariance. Ignoring inbreeding depression in the analytical model (.8 kg reduction of phenotypic value per 1% inbreeding) led to biased estimates of all genetic (co) variance components, all estimates being larger than the true values of the parameters. In particular, a negative bias in the direct-maternal genetic covariance was observed in analyses that ignored inbreeding depression. A small spurious sire-by-year interaction variance was also observed.

• 한국패류학회지
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• 제30권4호
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• pp.415-419
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• 2014

북방전복의 근친교배로 인한 근교약세현상의 유무를 명확히 하기 위하여 근친교배 2가계 (AA 및 BB)와 비근친교배 (ww1 및 ww2) 2가계를 같은날 동시에 생산하여 유생단계부터 동일한 수조에 혼합 사육관리한 후 친자확인 기술을 통하여 4개월째 및 10개월째 각각의 가계별 생존율 및 성장을 비교분석하였다. 성장의 경우, 4개월째 근친교배구 AA가계만이 비근친교배구 ww1 및 ww2가계보다 유의적으로 낮은 값으로 나타났지만, 10개월째는 근친교배구 AA가계 및 BB가계 모두 비근친교배구 ww1 및 ww2가계보다 유의적으로 낮은 값을 나타냈다. 또한 생존율에 있어서도 근친교배구가 비근친교배구에 비하여 낮은 값을 나타내었다. 이것은 한세대의 근친교배(근교계수 : 0.25) 에 있어서도 근교약세현상이 나타난다는 것을 보고하고 있다.

• 한국산학기술학회논문지
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• 제20권6호
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• pp.514-520
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• 2019

근친에 따른 개체의 능력저하 현상은 다양한 식물과 동물에서 밝혀져 왔다. 재래돼지는 국내 유일 품종이며 소규모 집단으로 유지되고 있어 국가차원에서 중요한 유전자원이다. 본 연구의 목적은 총산자수와 생존산자수에 대한 근교계수, 유전모수 및 근친퇴화 효과를 분석하는 것이다. 국립축산과학원에서 보유한 재래돼지 혈통 2,806두와 483개(1~5산차)의 번식성적을 보유한 모돈 303두의 자료를 활용하였다. 각 형질에 대한 유전모수 추정 후 혼합모형으로 근교계수에 대한 근친퇴화 효과를 분석하였다. 유전모수 추정결과, 총산자수와 생존산자수는 고도의 유전력을 유지하였다. 근교계수는 1998년에서 2017~2018년까지 꾸준히 증가하였으나, 각 형질에 대해 1998년 대비 2017~2018년의 능력감소는 확인되지 않았다. 근교계수 증가에 따라 총산자수의 유의적인 근친퇴화(p=0.03)가 확인되었지만, 생존산자수에서는 유의적인 근친퇴화가 없었다(p=0.41). 또한 두 형질 모두 근교계수와 육종가의 긍정적 상호작용이 확인되었다(p<0.05). 본 연구 결과, 재래돼지 산자수에 대한 근친퇴화 효과가 일부 확인되었지만, 세대가 지남에 따라 명확한 표현형 감소는 확인되지 않았다. 이는 현재까지 높은 유전효과로 근친퇴화를 극복할 수 있음을 시사한다.

• Animal Bioscience
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• 제34권4호
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• pp.506-515
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• 2021

Objective: Initial consequence of inbreeding is inbreeding depression which impairs the performance of growth, production, health, fertility and survival traits in different animal breeds and populations. The effect of inbreeding on economically important traits should be accurately estimated. The effect of inbreeding depression on growth traits in sheep has been reported in many breeds. Based on this, the main objective of the present research was to evaluate the impact of inbreeding on some growth traits of Iranian Baluchi sheep breed using quantile regression model. Methods: Pedigree and growth traits records of 13,633 Baluchi lambs born from year 1989 to 2016 were used in this research. The traits were birth weight, weaning weight, six-month weight, nine-month weight, and yearling weight. The contribution, inbreeding and co-ancestry software was used to calculate the pedigree statistics and inbreeding coefficients. To evaluate the impact of inbreeding on different quantiles of each growth trait, a series of quantile regression models were fitted using QUANTREG procedure of SAS software. Annual trend of inbreeding was also estimated fitting a simple linear regression of lamb's inbreeding coefficient on the birth year. Results: Average inbreeding coefficient of the population was 1.63 percent. Annual increase rate of inbreeding of the flock was 0.11 percent (p<0.01). The results showed that the effect of inbreeding in different quantiles of growth traits is not similar. Also, inbreeding affected differently on growth traits, considering lambs' sex and type of birth. Conclusion: Quantile regression revealed that inbreeding did not have similar effect on different quantiles of growth traits in Iranian Baluchi lambs indicating that at a given age and inbreeding coefficient, lambs with different sex and birth type were not equally influenced by inbreeding.

• Animal Bioscience
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• 제34권6호
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• pp.975-984
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• 2021

Objective: Inbreeding depression of reproduction is a major concern in the conservation of native chicken genetic resources. Here, based on the successful development of strongly inbred (Sinb) and weakly inbred (Winb) Langshan chickens, we aimed to evaluate inbreeding effects on reproductive traits and identify candidate genes involved in inbreeding depression of reproduction in Langshan chickens. Methods: A two-sample t-test was performed to estimate the differences in phenotypic values of reproductive traits between Sinb and Winb chicken groups. Three healthy chickens with reproductive trait values around the group mean values were selected from each of the groups. Differences in ovarian and hypothalamus transcriptomes between the two groups of chickens were analyzed by RNA sequencing (RNA-Seq). Results: The Sinb chicken group showed an obvious inbreeding depression in reproduction, especially for traits of age at the first egg and egg number at 300 days (p<0.01). Furthermore, 68 and 618 differentially expressed genes (DEGs) were obtained in the hypothalamus and ovary between the two chicken groups, respectively. In the hypothalamus, DEGs were mainly enriched in the pathways related to vitamin metabolism, signal transduction and development of the reproductive system, such as the riboflavin metabolism, Wnt signaling pathway, extracellular matrix-receptor interaction and focal adhesion pathways, including stimulated by retinoic acid 6, serpin family F member 1, secreted frizzled related protein 2, Wnt family member 6, and frizzled class receptor 4 genes. In the ovary, DEGs were significantly enriched in pathways associated with basic metabolism, including amino acid metabolism, oxidative phosphorylation, and glycosaminoglycan degradation. A series of key DEGs involved in folate biosynthesis (gamma-glutamyl hydrolase, guanosine triphosphate cyclohydrolase 1), oocyte meiosis and ovarian function (cytoplasmic polyadenylation element binding protein 1, structural maintenance of chromosomes 1B, and speedy/RINGO cell cycle regulator family member A), spermatogenesis and male fertility (prostaglandin D2 synthase 21 kDa), Mov10 RISC complex RNA helicase like 1, and deuterosome assembly protein 1) were identified, and these may play important roles in inbreeding depression in reproduction. Conclusion: The results improve our understanding of the regulatory mechanisms underlying inbreeding depression in chicken reproduction and provide a theoretical basis for the conservation of species resources.

• Asian-Australasian Journal of Animal Sciences
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• 제25권3호
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• pp.299-303
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• 2012

Inbreeding is the mating of relatives that produce progeny having more homozygous alleles than non-inbred animals. Inbreeding increases numbers of recessive alleles, which is often associated with decreased performance known as inbreeding depression. The magnitude of inbreeding depression depends on the level of inbreeding in the animal. Level of inbreeding is expressed by the inbreeding coefficient. One breeding goal in livestock is uniform productivity while maintaining acceptable inbreeding levels, especially keeping inbreeding less than 20%. However, in closed herds without the introduction of new genetic sources high levels of inbreeding over time are unavoidable. One method that increases selection response and minimizes inbreeding is selection of individuals by weighting estimated breeding values with average relationships among individuals. Optimum genetic contribution theory (OGC) uses relationships among individuals as weighting factors. The algorithm is as follows: i) Identify the individual having the best EBV; ii) Calculate average relationships ($\bar{r_j}$) between selected and candidates; iii) Select the individual having the best EBV adjusted for average relationships using the weighting factor k, $EBV^*=EBV_j(1-k\bar{{r}_j})$ Repeat process until the number of individuals selected equals number required. The objective of this study was to compare simulated results based on OGC selection under different conditions over 30 generations. Individuals (n = 110) were generated for the base population with pseudo random numbers of N~ (0, 3), ten were assumed male, and the remainder female. Each male was mated to ten females, and every female was assumed to have 5 progeny resulting in 500 individuals in the following generation. Results showed the OGC algorithm effectively controlled inbreeding and maintained consistent increases in selection response. Difference in breeding values between selection with OGC algorithm and by EBV only was 8%, however, rate of inbreeding was controlled by 47% after 20 generation. These results indicate that the OGC algorithm can be used effectively in long-term selection programs.

• Asian-Australasian Journal of Animal Sciences
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• 제18권10호
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• pp.1363-1367
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• 2005

A pedigree file of 4,738 records of a purebred flock of Muzaffarnagari sheep, maintained at Central Institute for Research on Goats (CIRG), Makhdoom, for a period of 24 years (1978 to 2001) was used to calculate inbreeding coefficients. The lambtraits studied were birth, 3, 6, 9 and 12 months weights as well as 6 and 12 months fleece yields. The lambs' and ewes' inbreeding coefficients ranged from 0 to 26.4% and 0 to 25%, respectively. The average inbreeding coefficient of lambs was higher than that of ewes in all periods as expected in a closed flock. Fluctuations in lamb and ewe inbreeding were observed in the periods under study. The percentages of animals in the higher inbred categories varied somewhat but generally were relatively constant. The mean rate of inbreeding was 0.63% per generation. The effective population size of the flock was 79.1. On average, an increase of 1% individual inbreeding significantly (p<0.05) reduced weights at birth by 0.010 kg, at 3 month by 0.048 kg, at 6 month by 0.075 kg, at 9 month by 0.129 kg and at 12 month by 0.112 kg. Ewes' inbreeding had non-significant effects on body weight at all ages. Effects of both lambs' and ewes' inbreeding had negative but non-significant effects on fleece weights at 6 and 12 months of age. Thus, inbreeding depression in lambs significantly reduced body weights from birth to 12 months of age but had a negligible effect on fleece yields.

• Asian-Australasian Journal of Animal Sciences
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• 제32권7호
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• pp.930-938
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• 2019

Objective: Estimate genetic parameters, the rate of inbreeding, and the effect of inbreeding on growth and egg production traits of a Thai native chicken breed Lueng Hang Kao Kabinburi housed under intensive management under a tropical climate. Methods: Genetic parameters were estimated for weight measured at four weekly intervals from body weight at day 1 (BW1D) to body weight at 24 weeks (BW24) of age, as well as weight at first egg, age at first egg (AFE), egg weight at first egg, and total number of eggs (EN) produced during the first 17 weeks of lay using restricted maximum likelihood. Inbreeding depression was estimated using a linear regression of individual phenotype on inbreeding coefficient. Results: Direct additive genetic effect was significant for all traits. Maternal genetic effect and permanent environmental hen effects were significant for all early growth traits, expect for BW24. For BW24, maternal genetic effect was also significant. Permanent environmental hen effect was significant for AFE. Direct heritabilities ranged from 0.10 to 0.47 for growth traits and ranged from 0.15 to 0.16 for egg production traits. Early growth traits had high genetic correlations between them. The EN was lowly negatively correlated with other traits. The average rate of inbreeding for the population was 0.09% per year. Overall, the inbreeding had no effect on body weight traits, except for BW1D. An increase in inbreeding coefficient by 1% reduced BWID by 0.09 g (0.29% of the mean). Conclusion: Improvement in body weight gain can be achieved by selecting for early growth traits. Selection for higher body weight traits is expected to increase the weight of first egg. Due to low but unfavorable correlations with body weight traits, selection on EN needs to be combined with other traits via multi-trait index selection to improve body weight and EN simultaneously.

• Asian-Australasian Journal of Animal Sciences
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• 제17권5호
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• pp.594-597
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• 2004

A pedigree file of 4,628 records of Muzaffarnagari sheep, maintained at Central Institute for Research on Goats (CIRG), Makhdoom, was used to calculate the inbreeding coefficient of the flock. The flock had been closed for about 25 years (1978 to 2002). The investigation was aimed to study the effects of inbreeding on survivability of lambs. The cumulative survivability of lambs i.e., lambs survived up to 3, 7 and 15 days, 1, 2, 3, 6, 9 and 12 months after birth was considered for the study. The average level of inbreeding of lambs was 1.60%, ranging from 0 to 26.4%. The average inbreeding coefficient of dam over the periods was 1.00% and it ranged from 0 to 25.0%. Significant (p<0.05) adverse effect of lamb's inbreeding was observed on survivability of lambs at all ages except up to 3 and 7 days after birth. On an average, 1% increase in individual inbreeding coefficient should reduce the 0.31, 0.34, 0.32, 0.31, 0.33, 0.44 and 0.49 percent lamb survival up to the age of 15 day and 1, 2, 3, 6, 9 and 12 months, respectively. Ewes inbreeding had non-significant effects on lamb survival at all ages.