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Model comparison for genetic evaluation of milk yield in crossbred Holsteins in the tropics

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Chanvijit K., Duangjinda M., Pattarajinda V., Reodecha C.

Journal of Applied Genetics

2005

vol. 46

issue 4

387-393

The objective of this study was to compare models for appropriate genetic parameter estimation for milk yield (305-day) in crossbred Holsteins in the tropics, where only records from crossbred cows were available. Eleven models with different effects of contemporary group (CG) at calving (herd-year-season or herd-year-month as fixed, and herd-year-month as random), age at calving (as linear or quadratic covariates, age-class, and age-class ? lactation), and dominance were considered. On-farm records from small herds (n < 50) were included or excluded to validate the parameter estimates. Average Information Restricted Maximum Likelihood (AIREML) and Best Linear Unbiased Prediction (BLUP) were used to estimate variance components and breeding values. R-square (R2) and standard error of heritability (h2) were used to determine the appropriate model. The estimates of heritability from most models ranged from 0.18 to 0.22. CG formation of herd-year-month as a random effect slightly lowered the additive genetic variance but considerably decreased the permanent environmental variance. The model with age-class ? lactation gave better R2 than other age adjustments. The models including records from smallholders gave similar estimates of heritability and a lower standard error than the models excluding them. The estimate of dominance variance as a proportion of total variance was close to zero. The low ratio of dominance to additive genetic variance suggested that the inclusion of dominance effects in the model was unjustified. In conclusion, the model including the effects of herd-year-month, age-class ? lactation, as well as additive genetic, permanent environmental and residual effects, was the most appropriate for genetic evaluation in crossbred Holsteins, where records from smallholders could be included.

Associations between 2 paternal casein haplotypes and milk yield traits of Swiss Fleckvieh cattle

100%

Braunschweig M. H.

Journal of Applied Genetics

2008

vol. 49

issue 1

69-74

Associations between casein haplotypes and milk yield traits of offspring from 5 Swiss Fleckvieh AI test bulls were investigated. The analysis was performed by using a daughter design, where each daughter inherited either paternal haplotype B-A1-A-A or B-A2-A-A for alleles of alpha s1-, beta, alpha s2- and -casein genes. The substitution effects of paternal CSN2 A1 versus A2 on protein yield deviations (YDs) were significant (P < 0.05), whereas their effects on milk and fat YDs were not. The paternal substitution effects of the CSN2 A1 versus the A2 allele on protein YDs within the 5 sires did not reach the significance level. This is due to the contrary allele substitution effect of a sire compared to the other 4 sires. The effects of maternal haplotypes on milk, protein and fat YDs were not significant. However, it is noteworthy that the effects of haplotypes with a low frequency in the population deviate largely from the most frequent haplotype B-A2-A-A. The effects of beta-lactoglobulin (BLG) genotypes were significant for protein YDs but not for milk and fat YDs. The association between the paternal CSN2 A1 and A2 alleles and milk protein YDs within sires but not milk and fat YDs indicate an interaction, which might be a consequence of CSN2 heterogeneity or a closely linked gene that is contributing to the estimated effects.

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2 Journal of Applied Genetics

1 2008

1 2005

1 Braunschweig M. H.

1 Chanvijit K.

1 Duangjinda M.

1 Pattarajinda V.

1 Reodecha C.

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Model comparison for genetic evaluation of milk yield in crossbred Holsteins in the tropics

Associations between 2 paternal casein haplotypes and milk yield traits of Swiss Fleckvieh cattle