Research funding for agriculture and food industry(FFL/JA)
About the project
We also want to investigate the impact of circadian shifts on the biological rhythm of the cows.
It is well known that lighting can affect production and fertility in our production animals. For the production of dairy cows, a long day (16 hours of light) with sufficient light intensity is favourable compared to shorter days (12 hours of light). This effect is partly due to increased feed intake with more light hours in the day, and partly due to stimulation of hormone secretion due to increased light duration.
Melatonin is often referred to as a sleep hormone and it plays an important role in the biological rhythm. Melatonin secretion is controlled by light; when light hits the eye, melatonin secretion decreases, while secretion increases in the absence of light. Since melatonin is associated with sleepiness, it is recommended that humans avoid blue light in the evening before going to sleep and instead ensure low light levels. Sleep in cows is spread throughout the day, but maintaining a natural production of melatonin is still important as the hormone affects the biological rhythm of cows and has an effect on other hormones. In addition to its direct effect, the growth hormone IGF-1 (Insulin-like growth factor 1) is stimulated by melatonin, which has a direct stimulating effect on milk production. This hormone is therefore one of the reasons for increased milk production during long days.
In a previous study conducted by us, we tested high light intensity during both day and night, and found that concentrations of IGF-1 were lower in cows that had constant high light intensity. This may be a sign that constant light can be unfavourable for milk production. In Norway, the law stipulates that cows should have sufficient light during the day, and that orientation light can be used at night. It is also stipulated that cattle must be allowed to rest from artificial light, although it is legal to have low lighting at night as well. A Norwegian study found that daytime light intensity varied between 4 and 160 lux in Norwegian stanchion barns, where 4 lux is clearly insufficient daytime lighting, while 160 lux is at the recommended level.
In loose housing barns with automatic milking systems (AMS), light is desirable around the clock to keep activity levels high and distribute the cows' time budget so that, for example, the milking robot is visited evenly throughout the day. For many, it is therefore attractive to have a relatively high light intensity even at night. A study in Swedish loose housing barns found that the light intensity was often at a level that would inhibit the hormone melatonin at night, which would not allow for a normal biological circadian rhythm.
Participants
NMBU participant
External participants
Emma Ternman, Nord Universitet
Stine Grønmo Kischel, TINE
Sigrid Agenäs, Sofia Lindkvist og Björn Ekesten, Swedish University of Agricultural Sciences (SLU):