title: The influence of oestrous substances on cyclicity and oestrous behaviour in dairy heifers.
abstract: BACKGROUND
  Declining fertility is a major concern for dairy farmers today. One explanation is shorter and weaker expression of oestrus in dairy cows making it difficult to determine optimal time for artificial insemination (AI). Chemical communication is of interest in the search for tools to detect oestrus or to synchronise or enhance oestrous periods. Pheromones, used in chemical communication within species, can influence reproduction in different ways. The aim here was to investigate whether oestrous cycle length, and duration and intensity of oestrous expression in dairy heifers could be manipulated through exposure to pheromones in oestrual substances from other females.
  
  
  METHODS
  Beginning on day 16 of two consecutive control oestrous cycles, ten heifers of the Swedish Red Breed (SRB) were exposed to water. During the two following cycles the heifers were exposed to urine and vaginal mucus, obtained from cows in oestrus. Cyclicity parameters were monitored through hormone measurements, oestrus detection and ultrasonographic examination.
  
  
  RESULTS
  We found no difference in cycle length or in duration of standing oestrus between control and treatment. We did, however, find a tendency of interaction between type of exposure (control or treatment) and cycle number within type of exposure for cycle length (p = 0.068), with the length differing less between the treatment cycles. We also found a tendency of effect of type of exposure on maximal concentration (p = 0.073) and sum of concentrations (p = 0.063) of LH during the LH surge, with values being higher for the control cycles. There were also significant differences in when the different signs of oestrus occurred and in the intensity of oestrous expression. The score for oedema and hyperaemia of external genitalia was significantly higher (p = 0.004) for the control cycles and there was also a significant interaction between type of exposure and time period for restlessness (p = 0.011), with maximum score occurring earlier for treatment cycles.
  
  
  CONCLUSIONS
  No evidence of altered oestrous cycle length or duration of oestrus after exposure of females to oestrous substances from other females was found. Expression of oestrus, and maybe also LH secretion, however, seemed influenced by the exposure, with the effect of treatment being suppressive rather than enhancing.
authors.affiliation: Department of Clinical Sciences, Division of Reproduction, Swedish University of Agricultural Sciences, PO Box 7054, SE-750 07 Uppsala, Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Nordéus
authors.forename: Renée
authors.initials: R
authors.lastname: Båge
authors.forename: Hans
authors.initials: H
authors.lastname: Gustafsson
authors.forename: Patrice
authors.initials: P
authors.lastname: Humblot
authors.forename: Lennart
authors.initials: L
authors.lastname: Söderquist
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood / Q000502:physiology*; D004958:Estradiol / Q000097:blood; D030762:Estrous Cycle / Q000502:physiology*; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood; D006080:Ovarian Follicle / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D012724:Sex Attractants / Q000494:pharmacology*
chemical_list: D012724:Sex Attractants; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone