The dairy industry has made large advances in efficiencies over the past 60 years as a result of changes in breeding, nutrition and management practices [1]. To meet the growing demand for dairy products, which is projected to continue out to the year 2050 [2], milk production per cow has increased over the last thirty years primarily by genetic selection and better nutrition. Genetic selection...

Due to genotype by environment interaction (GxE), conventional bulls might not be suitable for organic production circumstances. Therefore, lactation records from Holstein cows on organic and conventional farms were used to estimate the magnitude of GxE between organic and conventional production circumstances. GxE was quantified by estimating the genetic correlations between production traits ...

Random regression models (RRM) are used for genetic estimations of milk traits in dairy cows. RRM utilize data on traits that are repeated during the time, such as milk trait, which allows of the evaluation of the test day production information. In this study, to estimate genetic parameters for milk production trait, test day records (TDR) were collected from the first lactation of Holstein co...

Fertility, represented by calving interval, has been included in the genetic evaluation of Icelandic cattle since 1993. In spite this an unfavourable trend is seen and, recent implementation test-day models for milk production changed premise using interval to represent fertility. The aim study was estimate parameters and trends different female fertility traits dairy suggest new evaluation. In...

Intensive milk and beef production is COIlIIlPn to the European agricultural due to a high density of population. Milk and beef traits are involved in breeding objectives of dual-purpose cattle. Various dual-purpose cattle populations cover a wide range of economic ting of milk and beef. The optimal weights of milk and beef characters on the marginal change in profit, and the time and nUIlber o...

In the present study, records on 22872 first-parity Holsteins collected from 131 herds by the Animal Breeding and Improvement Center of Iran from 1995 to 2014 were considered to estimate genetic and phenotypic relationships between calving difficulty (CD) and the lactation curve traits, including initial milk yield (Ap), ascending (Bp) and descending (Cp) slope of the lactation curves, peak mil...

The objective of this study was to estimate effects of environmental sensitivity of milk production traits for several environmental parameters and to investigate the impact of combining traits with different environmental sensitivity in an economic index. Variance components and breeding values were estimated for milk, fat, and protein yield, and fat and protein percentage by applying a random...

The objective of this study was to determine the polymorphism of bovine β-lactoglobulin (β-LG) gene and its association with milk production traits in Iranian Najdi cattle. Blood samples were collected from 80 Najdi cattle from the Najdi cattle breeding station located in Shoshtar, Khuzestan. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) techniqus were used...