title: [Validity of the use of L-Tyrosine to enhance fertility of female domestic animals. A study on the evidence from the literature].
abstract: OBJECTIVE
  In order to improve fertility in female domestic animals, especially in bitches, several authors recommend the feeding of the amino acid L-Tyrosine during the follicular phase of the oestrous cycle. The aim of this article was a systematic and statistical analysis of current literature in terms of evidence-based medicine.
  
  
  METHODS
  Literature research, statistical analysis and classification in levels of evidence.
  
  
  RESULTS
  Fifteen German and two English studies on the effect of L-Tyrosine on the fertility in domestic animals were found. The statistical analysis and evaluation of evidence showed that most studies feature methodical deficits and often findings were inconsistent with one another.
  
  
  CONCLUSIONS
  Heterogeneous results indicate a considerable need for further research on the effectiveness and dose of L-Tyrosine to legitimate its appliance in practice.
authors.affiliation: Tierklinik für Fortpflanzung, Freie Universität Berlin, Königsweg 65, Haus 27, 14163 Berlin. heuwieser.wolfgang@vetmed.fu-berlin.de
authors.forename: S
authors.initials: S
authors.lastname: Spankowsky
authors.forename: S
authors.initials: S
authors.lastname: Arlt
authors.forename: G
authors.initials: G
authors.lastname: Arndt
authors.forename: W
authors.initials: W
authors.lastname: Heuwieser
mesh_terms: D000818:Animals; D000829:Animals, Domestic / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D055317:Evidence-Based Practice; D005260:Female; D005298:Fertility / Q000187:drug effects*; D005498:Follicular Phase / Q000187:drug effects; D014443:Tyrosine / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D014443:Tyrosine