Identification of the blue light intensity administered to one eye required to suppress bovine plasma melatonin and investigation into effects on milk production in grazing dairy cows

Abstract

Long-day photoperiod is known to positively affect milk production in confinement dairy systems, and it has been hypothesized that pineal melatonin (MT) secretion plays a substantial role in this process. Specialized mammalian photoreceptors that regulate MT secretion are optimally stimulated by short wavelength blue light. We investigated the blue light intensity administered to one eye required to suppress MT secretion in nonlactating dairy cows, and subsequently examined effects on milk production in grazing dairy cows. Following a 14-d light-dark 8:16 h environmental conditioning period, 5 nonlactating Holstein-Friesian cows were exposed to treatments of <1, 70, 125, 175, and 225 lx for 8 additional hours using a 5 × 5 Latin square design. Light was administered via headpieces fitted with light-emitting diodes emitting blue light (465 nm) to the right eye. All cows were then exposed to a light-dark 16:8 h cycle for one night via the indoor lighting system (>200 lx white light). Plasma samples collected at regular intervals were assayed for MT. A dose-dependent effect of light treatment on mean circulating MT concentrations (and 95% CI) was observed [9.4 (7.2, 12.3), 5.0 (3.8, 6.6), 4.4 (3.3, 5.7), 3.3 (2.5, 4.3) and 1.7 (1.3, 2.3) pg/mL for treatments of 0, 70, 125, 175, and 225 lx, respectively. Only the 225 lx treatment acutely suppressed plasma melatonin concentration to levels similar to the light-dark 16:8 h treatment [1.9 (1.4, 2.5) pg/mL]. Forty spring-calving cows were blocked on parity, calving date and Economic Breeding Index for milk production and assigned to the control treatment or blue light to a single eye (LT) treatment from calving through 32 wk of lactation. The cows assigned to LT treatment were fitted with headpieces providing 225 lx of blue light to the right eye from 1700 until 0000 h. Mean milk production (and 95% CI) during 32 wk of lactation was not affected by treatment [20.3 (19.3, 21.3) vs. 20.9 (19.8, 22.0) kg/d, control and LT, respectively]. Within multiparous cows, a treatment by week interaction was detected, whereby LT treatment increased milk production during the first 12 wk of lactation [25.8 (24.3, 27.3) vs. 28.0 (26.5, 29.5) kg/d; +8.5%], but had no effect thereafter. Treatment did not affect plasma insulin-like growth factor 1. We identified the blue light intensity to one eye required to acutely suppress MT concentrations. Transient favorable effects on milk production were observed in multiparous cows. It remains unclear how single-eye blue light treatment affects galactopoiesis in grazing dairy cows, and further research is needed to explore whether this modality of light delivery represents a useful means to aid productivity in pasture-based dairy systems.

Preferences of Dairy Cattle for Supplemental Light-Emitting Diode Lighting in the Resting Area

“…The intensity of light appears to have a dose-dependent effect on melatonin production. Both Murphy et al [ 13 ] and Lawson and Kennedy [ 30 ] observed that all light intensities decreased the melatonin concentration within the first few hours of exposure to darkness. However, Murphy et al [ 13 ] found that 225 lx of blue light was required to suppress plasma melatonin concentrations.…”

“…Both Murphy et al [ 13 ] and Lawson and Kennedy [ 30 ] observed that all light intensities decreased the melatonin concentration within the first few hours of exposure to darkness. However, Murphy et al [ 13 ] found that 225 lx of blue light was required to suppress plasma melatonin concentrations. In contrast, Lawson and Kennedy [ 30 ] found that 400 lx of fluorescent light was required for sustained melatonin inhibition.…”

“…This preference decreased in the third week, and in the fifth week, pigs did not have a preference for either colour temperature [ 17 ]. The observed effects of light exposure could also be shortly after exposure (e.g., 2 h), as seen in the plasma melatonin concentrations of dairy cows exposed to blue light (465 nm; [ 13 ]) and in humans exposed to blue-enriched light before sleeping [ 33 ]. Alternatively, responses may take a couple of weeks to be evident.…”

“…In contrast, there has been little work on the quality (wavelength) of light in dairy cattle. Blue light is known to suppress melatonin secretion in humans [ 6 ], dairy cows [ 13 ] and calves [ 14 ] and may decrease milk production [ 15 ]. Uncertainty still exists on how different wavelengths, whether individual or in combination, can be used to support production, growth, reproduction, and immune function in dairy cattle.…”

Effects of SNPs in AANAT and ASMT Genes on Milk and Peripheral Blood Melatonin Concentrations in Holstein Cows (Bos taurus)

“…Many studies have shown that livestock wool, milk, meat, and other production performances are strongly associated with SNPs in key regulatory genes [ 15 , 16 , 17 , 18 ]. As mentioned above, melatonin-enriched milk was obtained mostly by collecting night milk and controlling the light at night [ 11 , 12 , 19 , 20 ], and it ignored the innate melatonin synthesis potential regulated by genetic variations. Using SNP to identify cows with high milk melatonin levels is a novel approach to generate functional milk and it would be more reliable and efficient than that of light regulation.…”