Sex differences in mortality rates stem from multiple causes that are best understood when integrated in an evolutionary life history framework. This study investigates the relationship of sex differences in mortality rates across nations to indicators of the life history characteristics of populations. Controlling for gross national income per capita, the overall sex difference in mortality ra...

Genetic selection has made dairy cows more profit-able producers of milk. Genetic evaluations began with 2 traits measured on a few cows but now include many traits measured on millions of cows. Selection indexes from USDA included yield traits beginning in 1971, productive life and somatic cell score beginning in 1994, conformation traits in 2000, and cow fertility and calving ease in 2003. Th...

Genetic diversity among breeds of cattle allows producers to select animals for specific environments or market conditions. Reproductive efficiency is a multi-component trait that is largely influenced by environmental influences such as health and nutritional status; however, there are clearly genetic components to reproductive efficiency, and breed differences in a number of indicator traits ...

Milk yield per cow has more than doubled in the previous 40 years and many cows now produce more than 20,000 kg of milk per lactation. The increase in production should be viewed with concern because: i) the increase in milk yield has been accompanied by declining fertility, increasing leg and metabolic problems and declining longevity; ii) there are unfavourable genetic correlations between mi...

Conventional breeding schemes for dairy cattle are based on phenotypic information obtained from individuals and/or their relatives and progeny testing of the young bull candidates. The genetic model used in the evaluation process of the animals does not assume the underlying genes of the quantitative traits to be known. Knowing the chromosomal areas or actual genes affecting the traits would a...

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...

Many genetic markers related to health or production traits are not evaluated in populations independent of the discovery population or related to phenotype. Here we evaluated 68 single nucleotide polymorphisms (SNP) in candidate genes previously associated with genetic merit for fertility and production traits for association with phenotypic measurements of fertility in a population of Holstei...

Recent trends occurring in broiler primary breeding companies are described. The structure and operation of broiler primary breeder companies are described from pedigree elite populations, through great-grandparent and grandparent generations, down to the parent stock. The relatively low value of fertility and hatchability, compared with yield and feed efficiency as selection traits, is assesse...

Genotype x environment (GxE) interactions can reduce the accuracy of a model to predict the performance of an animal and have an undesirable influence if not accounted for when estimating breeding values. Consequently, identification of these GxE is necessary when considering a turkey breeding program. Reranking based on the genetic prediction of turkey egg production, fertility, and hatchabili...