All alterations in DNA function, without alterations in DNA sequence, are referred to as epigenetics. It is associated with gene expression and the expression of different phenotypes (appearance). These modifications are influenced by environmental factors and can be transferred to the progeny in cell lines and complex organisms, including livestock. The first evidence of epigenetic inheritance in humans resulted from the Dutch famine in 1944. Children of pregnant women exposed to the famine intra-uterine during late pregnancy were smaller than average and more susceptible to health problems. Surprisingly, some of these effects remained in the children of these children. Recent research, mostly on laboratory animals, has shown that diet, toxicants and even culture media in in-vitro fertilization can mediate epigenetic changes. The initial interest in genomic imprinting and epigenetics in livestock was driven by the occurrence of a fetal overgrowth syndrome during assisted reproduction techniques in ruminants. In poultry there are initiatives to use epigenetics for improved heat tolerance and “nutrigenomic” research for optimizing future broiler and broiler breeder performance. Since both milk and beef production can be influenced by environmental factors and epigenetic mechanisms, the use of epigenetics to manipulate milk and beef production is being investigated. The idea is that ‘soft’ or epigenetic inheritance is a more pliable system for the fine tuning of the next generation to novel environments than the slow reactivity of Mendelian ‘hard inheritance’. Both genetic and epigenetic controls influence genetic expression and should be taken into account when formulating breeding programs for changing environmental conditions.