• 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.

• 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.

• Asian-Australasian Journal of Animal Sciences
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• 제15권12호
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• pp.1686-1689
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• 2002

Genetic gains and inbreeding coefficients in a Holstein MOET breeding population were predicted under different conditions relating to the distribution of the number of transferable embryos collected per flush using Monte Carlo simulation. The numbers of transferable embryos collected per flush were determined using five distributions (distributions 1, 3, 5, 7 and 9) with different aspects and similar means. Distributions 1, 3, 5, 7 and 9 were assumed to have gamma distribution's parameters ($\alpha$ and $\beta$) of (1 and 4.4), (3 and 1.47), (5 and 0.88), (7 and 0.63) and (9 and 0.49), respectively. Inbreeding rates were statistically significantly different among distributions but genetic gains were not. Relationships between inbreeding rates and variances of family size could be were clearly distinguished. The highest inbreeding coefficients were predicted in distribution 1 with the largest variance of family size, while distributions 5, 7 and 9 with smaller variance of family size had lower inbreeding coefficients.

• Reproductive and Developmental Biology
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• 제37권3호
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• pp.123-127
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• 2013

The objective of this study was to compare the effects of the levels of inbreeding on body weight traits between two breed populations, Hanwoo and Korea Brindle cattle. Birth weight (BW), weaning weight (WW), body weight at 6 months of age (W6) and yearling weight (YW). Records of 1,745 calves (1,513 from Hanwoo, and 232 from Korea Brindle calves) were collected from Livestock Research Institutes in Kangwon, Gyeongbuk and Chungbuk provinces. The least squares means (LSM) and their standard errors for BW, WW, W6 and YW were $25.4{\pm}0.1$ kg, $81.0{\pm}1.8$ kg, $146.1{\pm}3.7$ kg and $291.5{\pm}2.4$ kg, respectively in Hanwoo calves and $22.6{\pm}0.3$ kg, $79.9{\pm}2.3$ kg, $137.6{\pm}4.6$ kg and $249.3{\pm}6.6$ kg, respectively in Korea Brindle calves. Pedigree data showed that 14.8% (316 out of 2131) of Hanwoo was inbred and the average inbreeding coefficient was 0.0209 (2.09%). Inbreeding coefficients of ten calves out of 316 total inbred Hanwoo calves were 12.5% or higher, whereas those of the other 306 calves were less than 12.5%. In both breeds, calves were divided into three groups of inbreeding classes - highly inbred group($F{\geq}0.125$), lowly to medially inbred group(0

• 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.

• Asian-Australasian Journal of Animal Sciences
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• 제14권5호
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• pp.597-602
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• 2001

This study was conducted to examine the relationships between the methods used to determine the number of transferable embryos collected per flush and the estimated cumulative genetic improvements in the Japanese Holstein MOET breeding population. Cumulative genetic improvements were predicted by Monte Carlo simulation using three different determination methods (MODEL 1, MODEL 2, and MODEL 3), for calculating the number of embryos collected per flush. Moreover EBVs were estimated including or ignoring coefficients of inbreeding in MME. Inbreeding coefficients were also predicted. The number of transferable embryos was determined using normal, gamma, and Poisson distributions in MODEL 1, gamma and Poisson distributions in MODEL 2, and only the Poisson distribution in MODEL 3. The fitness of MODEL 2 in relation to field data from Hokkaido Japan was the best, and the results for MODEL3 indicated that this model is unsuitable for determining the number of transferable embryos. The largest cumulative genetic improvement (3.11) in the 10th generation was predicted by MODEL 3 and the smallest (2.83) by MODEL 2. Mean coefficients of correlation between the true and estimated breeding values were 0.738, 0.729, and 0.773 in MODELS 1, 2, and 3, respectively. It is suggested that the smallest genetic improvement in MODEL 2 resulted from the smallest correlation coefficient between the true and estimated breeding values. The differences in milk, fat, and protein yields between MODELS 2 and 3 were 182.0, 7.0, and 5.6 kg, respectively, in real units when each trait was independently selected. The inbreeding coefficient was the highest (0.374) in MODEL 2 and the lowest (0.357) in MODEL 3. The effects of different methods for determining the number of transferable embryos per flush on genetic improvements and inbreeding coefficients of the simulated populations were remarkable. The effects of including coefficients of inbreeding in MME, however, were unclear.

• Asian-Australasian Journal of Animal Sciences
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• 제33권9호
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• pp.1369-1377
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• 2020

Objective: The main objectives of the present study were to assess the genetic diversity, population structure and to appraise the efficiency of ongoing selective breeding program in the closed nucleus herd of Nellore sheep through pedigree analysis. Methods: Information utilized in the study was collected from the pedigree records of Livestock Research Station, Palamaner during the period from 1989 to 2016. Genealogical parameters like generation interval, pedigree completeness, inbreeding level, average relatedness among the animals and genetic conservation index were estimated based on gene origin probabilities. Lambs born during 2012 and 2016 were considered as reference population. Two animal models either with the use of F_i or ΔF_i as linear co-variables were evaluated to know the effects of inbreeding on the growth traits of Nellore sheep. Results: Average generation interval and realized effective population size for the reference cohort were estimated as 3.38±0.10 and 91.56±1.58, respectively and the average inbreeding coefficient for reference population was 3.32%. Similarly, the effective number of founders, ancestors and founder genome equivalent of the reference population were observed as 47, 37, and 22.48, respectively. Fifty per cent of the genetic variability was explained by 14 influential ancestors in the reference cohort. The ratio f_e/f_a obtained in the study was 1.21, which is an indicator of bottlenecks in the population. The number of equivalent generations obtained in the study was 4.23 and this estimate suggested the fair depth of the pedigree. Conclusion: Study suggested that the population had decent levels of genetic diversity and a non-significant influence of inbreeding coefficient on growth traits of Nellore lambs. However, small portion of genetic diversity was lost due to a disproportionate contribution of founders and bottlenecks. Hence, breeding strategies which improve the genetic gain, widens the selection process and with optimum levels of inbreeding are recommended for the herd.

• 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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• 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.

• Genomics & Informatics
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• 제6권1호
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• pp.14-17
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• 2008

GENDISCAN study (Gene Discovery for Complex traits in Asian population of Northeast area) was designed to incorporate methodologies which enhance the power to identify genetic variations underlying complex disorders. Use of population isolates as the target population is a unique feather of this study. However, population isolates may have hidden inbreeding structures which can affect the validity of the study. To understand how this issue may affect results of GENDISCAN, we estimated inbreeding coefficients in two study populations in Mongolia. We analyzed the status of Hardy-Weinberg Equilibrium (HWE), polymorphism information contents (PIC), heterozygosity, allelic diversity, and inbreeding coefficients, using 317 and 1,044 STR (short tandem repeat) markers in Orkhontuul and Dashbalbar populations. HWE assumptions were generally met in most markers (88.6% and 94.2% respectively), and single marker PIC ranged between 0.2 and 0.9. Inbreeding coefficients were estimated to be 0.0023 and 0.0021, which are small enough to assure that conventional genetic analysis would work without any specific modification. We concluded that the population isolates used in GENDISCAN study would not present significant inflation of type I errors from inbreeding effects in its gene discovery analysis.