Effects of the circadian rhythm on milk composition in dairy cows: Does day milk differ from night milk?

Abstract

Metabolism in most organisms can show variations between the day and night. These variations may also affect the composition of products derived from livestock. The aim of the present study was to investigate the difference in composition between the day milk and night milk of dairy cows. Ten multiparous Holstein cows (milk yield = 25.2 ± 5.00 kg/d) were randomly selected during mid lactation. Milk samples were collected at 0500 h ("night milk") and 1500 h ("day milk") and analyzed to determine their composition. Mid-infrared spectroscopy was used to analyze macronutrient content of milk. Metabolomics and lipidomics were used to detect and analyze small molecules and fatty acids, respectively. An automatic biochemical analyzer and ELISA kits were used to determine biochemical indicators, as well as antioxidant and immune parameters in the milk. Though milk fat, protein, lactose, and total milk solids were not different between day milk and night milk, small molecules, metabolites and lipids, and hormones and cytokines differed between day milk and night milk. Regarding biochemical and immune-related indicators, the concentrations of malondialdehyde, HSP70, and HSP90 in night milk were lower than that in day milk. However, interferon-γ levels were higher in night milk. Additionally, night milk was naturally rich in melatonin. Lipidomics analyses showed that the levels of some lipids in night milk were higher than those in day milk. Metabolomics analyses identified 36 different metabolites between day milk and night milk. Higher concentrations of N-acetyl-d-glucosamine, cisaconitate, and d-sorbitol were observed in day milk. However, the other 33 metabolites analyzed, including carbohydrates, lipids, AA, and aromatic compounds, showed lower concentrations in day milk than in night milk. The present findings show that the composition of night milk differs considerably from that of day milk. Notable changes in the circadian rhythm also altered milk composition. These results provide evidence to support the strategic use and classification of day milk and night milk.

Microbiome-Metabolomics Insights into the Milk of Lactating Dairy Cows to Reveal the Health-Promoting Effects of Dietary Citrus Peel Extracts on the Mammary Metabolism

“…Previous studies reported that antioxidant activity in milk was improved significantly in cows fed diets supplemented with flavonoids [ 30 , 31 ]. As a marker of oxidative stress, MDA can indicate a counterbalance to high levels of oxidative phosphorylation [ 32 ]. The DPPH is a relatively stable organic radical widely used to test samples for its ability to scavenge free radicals [ 33 ].…”

The Effect of Short-Wavelength White LED Illumination throughout the Night on the Milk Fatty Acid Profile of High-Yielding Dairy Cows

“…In dairy cows, as in other organisms, most physiological parameters show a circadian output affected by photoperiod [ 15 , 16 ]. This has prompted investigations of within-day variations in milk composition, to differentiate between DM and NM from health-promoting, nutritional, and commercial perspectives [ 17 , 29 , 30 , 31 , 32 , 38 ]. As expected, most of these studies found circadian oscillation in milk yield and in some of the milk’s constituents, yet the presence and extent of the circadian variation varied between studies and depended on milking and feeding frequency [ 17 , 29 , 30 , 31 , 32 , 38 ].…”

“…This has prompted investigations of within-day variations in milk composition, to differentiate between DM and NM from health-promoting, nutritional, and commercial perspectives [ 17 , 29 , 30 , 31 , 32 , 38 ]. As expected, most of these studies found circadian oscillation in milk yield and in some of the milk’s constituents, yet the presence and extent of the circadian variation varied between studies and depended on milking and feeding frequency [ 17 , 29 , 30 , 31 , 32 , 38 ]. In this study, we mainly focused on the composition of fatty acids, due to their high nutritional value [ 39 ].…”

“…Moreover, many studies investigated the effect of season-induced change in photoperiod on milk fat composition (e.g., [ 46 , 47 ]). Yet, only a few recent studies investigated circadian variation in milk fat composition and its attenuation by photoperiod [ 29 , 32 ]. Thus, the novelty of this study is our aim of bridging this gap in existing knowledge.…”

“…Therefore, it has been an ongoing effort to explore ways to reduce the SFA levels in milk fat while increasing the unsaturated fatty acid (UFA) levels [ 27 , 28 ]. Notably, for some milk constituents (e.g., fat level), a circadian variation in milk fat composition has been found (i.e., a difference between DM (milked at 12:30 or 15:00) and NM (milked at 04:30 or 05:00)) [ 29 , 30 , 31 , 32 ]. Therefore, the present study’s first aim was to re-examine, in a controlled manner, the effect of W-LED LAN on dairy cows’ milk production and milk fat yields compared to a light regime of about 10 to 11 h of natural light.…”