Influence of Natural Sources of Biologically Active Substances on Livestock and Poultry Reproduction

Synthetic hormones and bioactive substances (vitamins, pigments and isoflavons) which have been used in the feed industry are accumulated in milk, meat and eggs. It is suspected that these are responsible for a number of side-effects such as carcinogenesis, liver and kidney damage, allergies in consumers. Furthermore the synthetic hormones, vitamins, pigments are less active than those extracted from natural sources. That is why there is a growing worldwide interest in finding new and safe biologically active substances from natural origin. The application of some natural no hormonal products increases the reproductive potential of male and female animals and poultry. These may improve gametogenesis, ovulation and sperm quality. The purpose of this overview is to present some natural sources of biologically active substances and to summarize their positive influence on reproduction in livestock and poultry.