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The effect of artificial photoperiod at the end of the breeding season on plasma testosterone concentrations in stallions
Author(s) -
COX JE,
REDHEAD PH,
JAWADS NMA
Publication year - 1988
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/j.1751-0813.1988.tb14308.x
Subject(s) - photoperiodism , seasonal breeder , zoology , testosterone (patch) , southern hemisphere , winter season , biology , artificial light , northern hemisphere , spring (device) , day length , ecology , climatology , endocrinology , botany , mechanical engineering , illuminance , physics , astronomy , geology , engineering
SUMMARY: Testosterone concentrations in stallions showed a seasonal trend with peak concentrations in the spring (April and May in Britain) and lowest concentrations in the period from December to February. The effect on this pattern of changing the length of the photoperiod at the end of the normal breeding season (mid‐summer's day) was studied in 2 experiments. In the first experiment artificial illumination was organised from 21 June to mimic the effect of transfer to a southern hemisphere spring and summer, that is short days becoming longer. The stallions had low concentrations of testosterone in February and high concentrations in April. Concentrations in July, August and September were extremely low with a return to high values in late Novemberlearly December. In the second experiment, illumination was maintained at the equivalent of a 16 1/2 hour day from 21 June to mid December. These stallions had high testosterone concentrations in April, after which they fell until August, later rising to a maximum in October. These after results are discussed in relation to transfer of stallions between the northern and southern hemispheres.