학술논문
Plasma melatonin and insulin-like growth factor-1 responses to dim light at night in dairy heifers.
Document Type
Article
Source
Subject
*MELATONIN
*HORMONES
*RADIOIMMUNOASSAY
*HEIFERS
*IMMUNODIAGNOSIS
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*
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Language
ISSN
0742-3098
Abstract
The effect of dim (5, 10 and 50 1x) light at night on night plasma melatonin level (NML) and night plasma insulin-like growth factor-1 (IGF-1) level was determined in 12 prepubertal Holstein heifers (245 ± 16 days age) using a 4 × 4 Latin Square design with 14-day treatment and 14-day recovery periods. Blood samples were collected at 23:00 hr (prior to the 8 hr night treatment which commenced at mid-night) on days 0, 3 and 13, and throughout the night at 01:00, 02:00, 03:00, 04:00, 06:00 and 08:00 hr on days 1, 4 and 14 of treatment. Plasma was analysed by radioimmunoassay for melatonin (all samples) and IGF-1 (samples for day 14, 04:00 hr only). Treatment ( P = 0.03) and treatment × time ( P = 0.02) were significant for NML. Exposure to 50 lx suppressed NML by 50% during the initial 2 hr of the night, but not thereafter. Exposure to 5 and 10 lx had no effect on NML. The NML response to 50 lx was found on all treatment days studied (treatment × time × day; P = 0.99). There was no treatment effect on plasma IGF-1 level ( P = 0.89), but plasma IGF-1 level was higher ( P = 0.001) during period 4. Plasma IGF-1 level and NML tended ( P = 0.10) to be negatively correlated. Light intensities of 10 lx or less appear safe for use at night in dairy barns where darkness is recommended. [ABSTRACT FROM AUTHOR]