Heat Stress in Dairy Cattle Alters Lipid Composition of Milk

Abstract

Heat stress, potentially affecting both the health of animals and the yield and composition of milk, occurs frequently in tropical, sub-tropical and temperate regions. A simulated acute heat stress experiment was conducted in controlled-climate chambers and milk samples collected before, during and after the heat challenge. Milk lipid composition, surveyed using LC-MS, showed significant changes in triacylglycerol (TAG) and polar lipid profiles. Heat stress (temperature-humidity index up to 84) was associated with a reduction in TAG groups containing short- and medium-chain fatty acids and a concomitant increase in those containing long-chain fatty acids. The abundance of five polar lipid classes including phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, lysophosphatidylcholine and glucosylceramide, was found to be significantly reduced during heat stress. Lysophosphatidylcholine, showing the greatest reduction in concentration, also displayed a differential response between heat tolerant and heat susceptible cows during heat stress. This phospholipid could be used as a heat stress biomarker for dairy cattle. Changes in TAG profile caused by heat stress are expected to modify the physical properties of milk fat, whereas the reduction of phospholipids may affect the nutritional value of milk. The results are discussed in relation to animal metabolism adaptation in the event of acute heat stress.

The Effects of Evaporative Cooling on Heat Stressed Dairy Holstein Cows Under a Semi-Arid Environment in Riyadh Area, Saudi Arabia

“…In addition, THI values of 70-72 units or less are considered acceptable [17], while a THI greater than 72 units causes a reduction in dry matter intake and milk production and composition manifested by having reduced fat, protein and casein contents in dairy cows [14,25]. In addition, a THI index of up to 84 was associated with reduction in triacylglycerol and polar lipid profiles [26]. Furthermore, an increased THI resulted in increased incidence of mastitis in cows [27].…”

Review: Challenges for dairy cow production systems arising from climate changes

“…Controversial results have been published for the effects of heat stress on milk fat content. Changes in triacylglycerol (TAG) profile and reduced phospholipid levels caused by heat stress were described by Liu et al (2017), what might modify the characteristics of milk fat (e.g. fatty acid composition).…”

Dairy cows – an opportunity in the research field of non-genetic inheritance?

“…The best studied adult stressor in dairy cows is heat stress [ 73 ] and its effects on milk are well characterized: Heat stress increases total protein, albumin, glucose, pO2 and lowers lactate levels [ 2 , 3 ]. LC–MS mass spectrometry on milk from heat stressed cows also reveals altered profiles of triacylglycerol (TAG) and polar lipid profiles [ 74 ]. These effects may be in part due to reduced food intake, and in part attributed to direct metabolic effects on the mammary glands [ 75 , 76 ].…”