Characteristics of progeny-test (PT) programs of artificial insemination (AI) organizations in the United States were examined for changes since 1960. Mean number of bulls that were progeny tested annually by major AI organizations during the mid 1990s was 11 for Ayrshires, 24 for Brown Swiss, 21 for Guernseys, 1261 for Holsteins, 112 for Jerseys, and 3 for Milking Shorthorns. Mean parent age a...

OBJECTIVE Calving ease (CE) is a complex reproductive trait of economic importance in dairy cattle. This study was aimed to investigate the genetic merits of CE for Holsteins in Korea. METHODS A total of 297,614 field records of CE, from 2000 to 2015, from first parity Holstein heifers were recorded initially. After necessary data pruning such as age at first calving (18 to 42 mo), gestation ...

The present study was performed to study the genetic relationship of productive life with production and type traits of Korean Holsteins at first three lactations. The data for the analysis from 56,054, 28,997, and 11,816 animals of first, second and third parity cows which were born from 2006 to 2011 were collected by Dairy Cattle Improvement Center, National Agricultural Co-operative Federati...

BACKGROUND Gene expression of lymphocytes was found to be influenced by histone methylation in mammals and trimethylation of lysine 27 on histone H3 (H3K27me3) normally represses genes expressions. Peripheral blood lymphocytes are the main source of somatic cells in the milk of dairy cows that vary frequently in response to the infection or injury of mammary gland and number of parities. METH...

If genetic evaluations are calculated with a single-trait repeatability model, evaluation changes may be attributed in part to bulls that have daughters that deviate considerably from the typical response to aging. Differences in maturity rate of bull daughters were examined to determine whether they influence change in bull evaluations. Standardized milk records for Holsteins that first calved...

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...

Pure Holsteins (n = 380) were compared to Normande/Holstein crossbreds (n = 245), Montbeliarde/Holstein crossbreds (n = 494), and Scandinavian Red/Holstein crossbreds (n = 328) for 305-d milk, fat, and protein production during first lactation. Scandinavian Red was a mixture of Swedish Red and Norwegian Red. Cows were housed at 7 commercial dairies in California and calved from June 2002 to Jan...

Calving difficulty is a trait that greatly affects animal welfare, herd profitability, and the amount of labor required by cattle farmers. It is influenced by direct and maternal genetic components. Selection and breeding strategies can optimize the accuracy of genetic evaluations and correctly emphasize calving difficulty in multiple-trait indices provided there are accurate estimates of genet...

Modeling extended lactations for the US Holsteins is useful because a majority (>55%) of the cows in the present population produce lactations longer than 305 d. In this study, 9 empirical and mechanistic models were compared for their suitability for modeling 305-d and 999-d lactations of US Holsteins. A pooled data set of 4,266,597 test-day yields from 427,657 (305-d complete) lactation recor...