Jattawa, D.;Koonawootrittriron, S.;Elzo, M.A.;Suwanasopee, T.
Asian-Australasian Journal of Animal Sciences
/
제25권9호
/
pp.1216-1222
/
2012
Somatic cells count (SCC), milk yield (MY) and pedigree information of 2,791 first lactation cows that calved between 1990 and 2010 on 259 Thai farms were used to estimate genetic parameters and trends for SCC and its genetic association with MY. The SCC were log-transformed (lnSCC) to make them normally distributed. An average information-restricted maximum likelihood procedure was used to estimate variance components. A bivariate animal model that considered herd-yr-season, calving age, and regression additive genetic group as fixed effects, and animal and residual as random effects was used for genetic evaluation. Heritability estimates were 0.12 (SE = 0.19) for lnSCC, and 0.31 (SE = 0.06) for MY. The genetic correlation estimate between lnSCC and MY was 0.26 (SE = 0.59). Mean yearly estimated breeding values during the last 20 years increased for SCC (49.02 cells/ml/yr, SE = 26.81 cells/ml/yr; p = 0.08), but not for MY (0.37 kg/yr, SE = 0.87 kg/yr; p = 0.68). Sire average breeding values for SCC and MY were higher than those of cows and dams (p<0.01). Heritability estimates for lnSCC and MY and their low but positive genetic correlation suggested that selection for low SCC may be feasible in this population as it is in other populations of dairy cows. Thus, selection for high MY and low SCC should be encouraged in Thai dairy improvement programs to increase profitability by improving both cow health and milk yield.
The objectives of the study were to examine non-genetic factors that influence somatic cell counts in dairy cattle and to estimate the genetic parameters of somatic cell counts. A total of 34, 097-test day somatic cell count records were obtained from the Zimbabwe Dairy Services Association (ZDSA). The data were from 5, 615 Holstein daughters of 390 sires and 2, 541 dams tested between May 1994 and December 1998. First lactation cows contributed 22, 147 records to the data set, while 11, 950 records were from second and later parity cows. The model for analysis included fixed effects of month of calving, year of calving, stage of lactation, calving interval and test date. Milk yield and age on test day were fitted in the model as covariates. The additive genetic effects pertaining to cows, sires and dams and the residual error were the random effects. The Average Information Restricted Maximum Likelihood algorithm was used for analysis. The heritability of somatic cell scores was low at $0.027{\pm}0.013$ for parity one cows and $0.087{\pm}0.031$ for parity two and above. Repeatability estimates were $0.22{\pm}0.01$ and $0.30{\pm}0.01$ for the two lactation groups, respectively. Genetic and phenotypic correlations between the somatic cell scores and test day milk production were small and negative. It seems that there is no genetic link between somatic cell counts and milk yield in Holstein cattle in Zimbabwe. The results also seem to indicate that somatic cell count is a trait that is mainly governed by environmental factors.
A study was conducted to assess the genetic diversity among Simmental Cross cattle in West Sumatra using microsatellite DNA markers. A total of 176 individual cattle blood samples was used for obtaining DNA samples. Twelve primers of microsatellite loci as recommended by FAO were used to identify the genetic diversity of the Simmental Cross cattle population. Multiplex DNA fragment analysis method was used for allele identification. All the microsatellite loci in this study were highly polymorphic and all of the identified alleles were able to classify the cattle population into several groups based on their genetic distance. The heterozygosity values of microsatellite loci in this study ranged from 0.556 to 0.782. The polymorphism information content (PIC) value of the 12 observed loci is high (PIC>0.5). The highest PIC value in the Simmental cattle population was 0.893 (locus TGLA53), while the lowest value was 0.529 (locus BM1818). Based on the genetic distance value, the subpopulation of the Simmental Cross-Agam and the Simmental Cross-Limapuluh Kota was exceptionally close to the Simmental Purebred thus indicating that a grading-up process has taken place with the Simmental Purebred. In view of the advantages possessed by the Simmental Cross cattle and the evaluation of the genetic diversity results, a number of subpopulations in this study can be considered as the initial (base) population for the Simmental Cross cattle breeding programs in West Sumatra, Indonesia.
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 Fi or ΔFi 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 fe/fa 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.
The objective of this study was to estimate the genetic parameters of milk protein yields in Iranian Holstein dairy cattle. A total of 1,112,082 test-day milk protein yield records of 167,269 first lactation Holstein cows, calved from 1990 to 2010, were analyzed. Estimates of the variance components, heritability, and genetic correlations for milk protein yields were obtained using a random regression test-day model. Milking times, herd, age of recording, year, and month of recording were included as fixed effects in the model. Additive genetic and permanent environmental random effects for the lactation curve were taken into account by applying orthogonal Legendre polynomials of the fourth order in the model. The lowest and highest additive genetic variances were estimated at the beginning and end of lactation, respectively. Permanent environmental variance was higher at both extremes. Residual variance was lowest at the middle of the lactation and contrarily, heritability increased during this period. Maximum heritability was found during the 12th lactation stage ($0.213{\pm}0.007$). Genetic, permanent, and phenotypic correlations among test-days decreased as the interval between consecutive test-days increased. A relatively large data set was used in this study; therefore, the estimated (co)variance components for random regression coefficients could be used for national genetic evaluation of dairy cattle in Iran.
Objective: During the last decade, genetic evaluation of dairy cows using longitudinal data (test day milk yield or 305-day milk yield) using random regression method has been officially adopted in several countries. The objectives of this study were to estimate covariance functions for genetic and permanent environmental effects and to obtain genetic parameters of 305-day milk yield over seven parities. Methods: Data including 60,279 total 305-day milk yield of 17,309 Iranian Holstein dairy cows in 7 parities calved between 20 to 140 months between 2004 and 2011. Residual variances were modeled by homogeneous and step functions with 7 and 10 classes. Results: The results showed that a third order polynomial for additive genetic and permanent environmental effects plus a step function with 10 classes for the residual variance was the most adequate and parsimonious model to describe the covariance structure of the data. Heritability estimates obtained by this model varied from 0.17 to 0.28. The performance of this model was better than repeatability model. Moreover, 10 classes of residual variance produce the more accurate result than 7 classes or homogeneous residual effect. Conclusion: A quadratic Legendre polynomial for additive genetic and permanent environmental effects with 10 step function residual classes are sufficient to produce a parsimonious model that explained the change in 305-day milk yield over consecutive parities of Iranian Holstein cows.
The collection, evaluation and conservation of crop germplasm have been treated as one of the basics to breeding program. An understanding of genetic relationships among germplasm resources is vital for future breeding process like yield, quality, and resistance. In the present study, EST-SSR markers were employed to assess the polymorphism and genetic diversity of 192 accessions of Proso millet preserved in the National Agrobiodiversity Center of RDA. We evaluated the efficiency of EST-SSR markers developed for proso millet species. A total of 98 alleles were detected with an average allele number of 4.5 per locus among 192 proso millet millet accessions using 22 EST-SSR markers. The averaged values of gene diversity ($H_E$) and polymorphism information content (PIC) for each EST-SSR marker were 0.362 and 0.404 within populations, respectively. Our results showed the moderate level of the molecular diversity among the proso millet accessions from diverse countries. A phylogenetic tree revealed three major groups of accessions that did not correspond with geographical distribution patterns with a few exceptions. The less correlation between the clusters and their geographic location might be considered due to their type difference. Our study provided a better understanding of genetic relationships among various germplasm collections, and it could contribute to more efficient utilization of valuable genetic resources. The EST-SSR markers developed here will serve as a valuable resource for genetic studies, like linkage mapping, diversity analysis, quantitative trait locus/association mapping, and molecular breeding.
This study was performed to investigate genetic relationship of age at first calving (AFC) with body development and reproduction capacity in female Hanwoo. The data sets of 52,299 reproduction records of 19,566 heads calved from 2011 to 2019 and conformation records of 19565 heads born from 1997 to 2017 were analyzed by separating them based on age at first calving. In the analysis, conformation traits included the body condition score (BCS), height (HT), body width (BW), hip bone length (HL), hip bone width (HW), and final score (FS). The heritability and genetic correlation of AFC with conformation traits and calving interval (CI) were analyzed. The heritability for AFC was 0.716, 0.087, and 0.097 for the before and after 24 months and combined data, respectively. The genetic correlation of AFC before 24 months with BCS was -0.778, -0.600 with BW, and 0.442 with HT. The genetic correlation of AFC after 24 months with HT was -0.826, -0.706 with BW, -0.623 with HL, -0.456 with HW, and -0.675 with FS. When the first calving age of young heifers approached 24 months, BCS and BW decreased, and HT increased. When first calving is delayed to after 24 months, the conformation traits become smaller, which indicates that conformation to some extent affects the delay in AFC. The genetic correlation between CI and AFC was -0.116, 0.307, and 0.250 for the before and after 24 month of AFC and combined data, respectively. When first calving date approached 24 months, CI was reduced. The obtained results suggest that it is important that first calving occurs at an appropriate age. Additional research is needed to perform proper genetic evaluation of first calving age in Hanwoo cattle in Korea.
Molecular characterization of different genotypes reveals accurate information about the degree of genetic diversity that helps to develop a proper breeding program. In this study, a total of 30 EST-based simple sequence repeat (EST-SSR) markers derived from trumpet lily (Lilium longiflorum) were used across 11 native lily species for their genetic relationship. Among these 30 markers, 24 SSR markers that showed polymorphism were used for evaluation of diversity spectrum. The allelic number at per locus ranged from 1 at SSR2 locus to 34 alleles at SSR15 locus, with an average of 11.25 alleles across 24 loci observed. The polymorphic information content, PIC, values ranged from 0.0523 for SSR9 to 0.9919 for SSR2 in all 24 loci with an average of 0.3827. The allelic frequency at every locus ranged from 0.81% at SSR2 locus to 99.6% at SSR14 locus. The pairwise genetic dissimilarity coefficient revealed the highest genetic distance with a value of 81.7% was in between L. dauricum and L. amabile. A relatively closer genetic distance was found between L. lancifolium and L. dauricum, L. maximowiczii and L. concolor, L. maximowiczii and L. distichum (Jeju), L. tsingtauense and L. callosum, L. cernuum and L. distichum (Jeju ecotype), of which dissimilarity coefficient was 50.0%. The molecular fingerprinting based on microsatellite marker could serve boldly to recognize genetically distant accessions and to sort morphologically close as well as duplicate accessions.
Objective: The objective of this study was to investigate the genetic components of daily milk yield and to re-rank bulls in South Korea by estimated breeding value (EBV) under heat stress using the temperature-humidity index (THI). Methods: This study was conducted using 125,312 monthly test-day records, collected from January 2000 to February 2017 for 19,889 Holstein cows from 647 farms in South Korea. Milk production data were collected from two agencies, the Dairy Cattle Genetic Improvement Center and the Korea Animal Improvement Association, and meteorological data were obtained from 41 regional weather stations using the Automated Surface Observing System (ASOS) installed throughout South Korea. A random regression model using the THI was applied to estimate genetic parameters of heat tolerance based on the test-day records. The model included herd-year-season, calving age, and days-in-milk as fixed effects, as well as heat tolerance as an additive genetic effect, permanent environmental effect, and direct additive and permanent environmental effect. Results: Below the THI threshold (${\leq}72$; no heat stress), the variance in heat tolerance was zero. However, the heat tolerance variance began to increase as THI exceeded the threshold. The covariance between the genetic additive effect and the heat tolerance effect was -0.33. Heritability estimates of milk yield ranged from 0.111 to 0.176 (average: 0.128). Heritability decreased slightly as THI increased, and began to increase at a THI of 79. The predicted bull EBV ranking varied with THI. Conclusion: We conclude that genetic evaluation using the THI function could be useful for selecting bulls for heat tolerance in South Korea.
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