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R Q Yang

Publications and source records attributed to R Q Yang.

7 recordsLinked to original sources
PubMed2007

Estimation of genetic parameters for cumulative egg numbers in a broiler dam line by using a random regression model.

The random regression model (RRM) methodology was applied to the estimation of genetic parameters for cumulative egg numbers and monthly egg production in a broiler dam line. The data were extracted from records of a commercial dam line in 2001 to 2003. A total of 99,193 records from 6,475 hens and 9,111 pedigreed animals were used in the current study. The variance components were estimated using Gibbs sampling procedure. According to the Bayesian information criterion and Bayes factor, an RRM with Legendre polynomial of 2 orders for hatching groups and additive genetic effects and of 4 orders for permanent environmental effects was chosen as the optimal model for cumulative egg numbers in the broiler dam line. The heritability estimates of the cumulative egg numbers between wk 1 and 40 of production ranged from 0.16 to 0.54, whereas heritability estimates from wk 12 to 20 of production were moderate. The ratios of permanent environmental variance to phenotypic variance were large, indicating that the RRM could produce better estimates of additive genetic effects. The genetic and phenotypic correlations between cumulative egg numbers at different production weeks estimated with the optimal RRM were generally higher when the overlapping weeks were greater. In addition, genetic parameters for monthly egg production could also be obtained by the optimal RRM, and the heritability estimates ranged from 0.03 to 0.18. It was suggested that early selection based on cumulative egg numbers in the first 19 wk of production could effectively improve annual egg production in the broiler dam line.

Animals↗
PubMed2006

Short communication: Optimal random regression models for milk production in dairy cattle.

Legendre polynomials of orders 3 to 8 in random regression models (RRM) for first-lactation milk production in Canadian Holsteins were compared statistically to determine the best model. Twenty-six RRM were compared using LP of order 5 for the phenotypic age-season groupings. Variance components of RRM were estimated using Bayesian estimation via Gibbs sampling. Several statistical criteria for model comparison were used including the total residual variance, the log likelihood function, Akaike's information criterion, the Bayesian information criterion, Bayes factors, an information-theoretic measure of model complexity, and the percentage relative reduction in complexity. The residual variance always picks the model with the most parameters. The log likelihood and information-theoretic measure picked the model with order 5 for additive genetic effects and order 7 for permanent environmental effects. The currently used model in Canada (order 5 for both additive and permanent environmental effects) was not the best for any single criterion, but was optimal when considering all criteria.

Animals↗
PubMed2005

Estimation of genetic parameters for lactational milk yields using two-dimensional random regressions on parities and days in milk in Chinese Simmental cattle.

A two-dimensional random regression model with regressions on days in milk (DIM) and parity number was applied to lactational milk yields in Chinese Simmental cattle. Random regressions were fitted for additive genetic and permanent environmental effects using a two-dimensional polynomial on DIM and parity number. A total of 4340 lactational milk yields from Chinese Simmental cattle which calved between 1980 and early 2000 were used in this study. Variance components were estimated using Bayesian methodology via Gibbs sampling. Variances of random regression coefficients associated with all terms of the polynomials were significant. A covariance function showed that heritabilities of lactational milk yields between 200 and 400 DIM over parities varied between 0.25 and 0.45. Heritabilities of 305-day milk yields from 1st to 6-8th parities were 0.28, 0.30, 0.32 0.32, 0.32, and 0.31, respectively. Ratios of permanent environment variances to total variances at each DIM were greater than corresponding heritabilities. Generally, genetic correlations were higher between lactational milk yields with similar DIM and parity number.

Animals↗
PubMed2001

[A study on the recombinant 26 kDa glutathione-S-transferase as a vaccine candidate: dynamics of antibodies in immunized buffaloes and protection against Schistosoma japonicum infections].

OBJECTIVE: To observe the dynamics of antibodies and protection against Schistosoma japonicum infections in buffaloes after immunized with recombinant 26 kDa glutathione-S-transferase (reSjc26GST). METHODS: Buffaloes in 2 villages endemic for schistosomiasis japonica were selected as test and control groups, respectively. In test group initially 96 buffaloes were vaccinated with reSjc26GST, and 90 buffaloes in the control group did not experience vaccination. The indicators included levels of antibodies to reSjc26GST in buffaloes before and after infection with S. japonicum and changes in infection rate. RESULTS: Specific antibodies, which showed a trend of trapezoid increase, were induced in buffaloes after immunized with reSjc26GST. Twenty months after immunization, the infection rate of the test group was decreased by 62.2% when compared with that before vaccination, and by 67.7% when compared with that of the control in the corresponding period. CONCLUSION: Specific antibodies and a certain extent of protection were induced in buffaloes after immunized with reSjc26GST, which played an significant role in ameliorating morbidity.

Animals↗