Multivariate genetic analysis of productive and reproductive traits in first lactation Holsteins in arid climate of Iran

Estimates of genetic parameters for traits of economic importance in dairy cattle are necessary for implementing efficient breeding programs. Accurate heritability and correlation estimates are required to predict expected selection response and to obtain predicted breeding values using mixed model procedures. Traits related to milk, fat, and protein production, conformation, length of productive life, reproduction, workability, and health are included in breeding programs of dairy cattle in many countries to maximize improvement of a breeding goal involving traits related to income and costs. Extreme or rapid changes in environmental conditions can often be detrimental to cattle performance. The objective of this study was the genetic analysis of productive and reproductive traits of Holstein dairy cows in arid climate of Iran using multivariate animal model.
Material and Data from 5403 first lactation Iranian Holsteins collected by the Animal Breeding Center of Iran during 1996 to 2009 was used for the multivariate genetic analysis of productive (milk, fat and protein yield, fat, protein percentage) and reproductive traits (length of dry period, age at first calving and calving interval). According to weather conditions, geographical location of herds and De Martonne’s global classification five climate groups (arid, semiarid, Mediterranean, semi humid and humid) were identified. Provinces: Semnan, Yazd, Southern Khorasan, Ghom, Sistan and Bluchestan, Kerman were in the arid class. Variance components, breeding values and genetic and phenotypic correlations were estimated by restricted maximum likelihood method using DMU package.
Genetic and phonotypic trends were computed as a linear regression of yearly means on calving year using the REG procedure of SAS 9.2.
The estimated heritabilities were 0.23, 0.27, 0.28, 0.39, 0.41, 0.03, 0.05, 0.25 and 0.054 for milk, fat and protein yield, fat and protein percentage, length of dry period, age at first calving and calving interval, respectively. The range of absolute genetic correlations was varied from 0.0.01 for fat yield-length of dry days to 0.84 for milk-protein yield and absolute phenotypic correlations were from 0.01 for protein-fat yield, and age at first calving-protein percentage to 0.91 for milk-protein yield. Genetic trends (for daughters) for milk, protein yield and protein percentage were, respectively, 4.48±0.88, 0.08±0.03 kg and -0.001±0.0002 % (P The results showed that for all traits in the study, phenotypic trend was statistically significant and favorable. For milk and protein yield of Holsteins in arid climate of Iran, the genetic trend was positive and significant.