title: Potential factors affecting semen quality in the Asian elephant (Elephas maximus).
abstract: BACKGROUND
  One of the major obstacles in using artificial insemination to manage genetics of elephant population in captivity is the large variations in semen quality among ejaculates within the same and among individuals. The objectives of this study were to determine the influences of (1) age (2) seasonality (3) and circulating testosterone (SrTest), triiodothyronine (SrT3) and tetraiodothyronine (SrT4), as well as seminal (4) testosterone (SpTest), zinc (SpZn) and protein (SpTP) on semen quality in the Asian elephant
  
  
  METHODS
  Analyses, including motility, viability and morphology were performed in semen samples collected twice monthly from 13 elephant bulls (age range, 10-to 72-years) by manual stimulation between July 2004 and June 2005. Serum samples obtained monthly were assessed for SrTest, SrT3, SrT4, and seminal plasma samples were evaluated for, SpTest, SpZn and SpTP.
  
  
  RESULTS
  The highest semen quality was observed at age 23 to 43 years. Percentages of progressive motility and viable sperm were lowest at age 51 to 70 years (P < 0.05); on the other hand, sperm concentration was lowest at age 10 to 19 years (P < 0.05). Percentage of sperm with normal morphology was highest at age 23 to 43 years. The levels of SrT3, SrTest, SpTest and SpZn were lowest at age 51 to 70 years, whereas SrT4 was lowest at age 23 to 43 years. Seasonality significantly affected semen characteristics in which percentage of viable sperm and cell concentration were highest during rainy season and lowest during summer months (P < 0.05). However, percentage of sperm with normal morphology was highest in summer and lowest in rainy season (P < 0.05). Seasonality significantly influenced SrTest with elevated concentrations observed in rainy season and winter (P < 0.05).
  
  
  CONCLUSIONS
  This study indicates that age and seasonality had influence on semen characteristics in the Asian elephant. The knowledge obtained in this study will improve our understanding of the reproductive biology of this species.
authors.affiliation: Faculty of Veterinary Medicine, Kasetsart University, Nakhonpathom 73140, Thailand. nthongtip@yahoo.com
authors.forename: Nikorn
authors.initials: N
authors.lastname: Thongtip
authors.forename: Jumnian
authors.initials: J
authors.lastname: Saikhun
authors.forename: Sittidet
authors.initials: S
authors.lastname: Mahasawangkul
authors.forename: Kornchai
authors.initials: K
authors.lastname: Kornkaewrat
authors.forename: Pornsawan
authors.initials: P
authors.lastname: Pongsopavijitr
authors.forename: Nucharin
authors.initials: N
authors.lastname: Songsasen
authors.forename: Anuchai
authors.initials: A
authors.lastname: Pinyopummin
mesh_terms: D000367:Age Factors; D000818:Animals; D004606:Elephants / Q000097:blood / Q000502:physiology*; D008297:Male; D011506:Proteins / Q000032:analysis; D011786:Quality Control; D012621:Seasons; D012661:Semen / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D013739:Testosterone / Q000032:analysis / Q000097:blood; D013963:Thyroid Hormones / Q000097:blood; D015032:Zinc / Q000032:analysis
chemical_list: D011506:Proteins; D013963:Thyroid Hormones; D013739:Testosterone; D015032:Zinc