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The effect of climate change on dairy production
The long-lasting adverse physiological effects of climate change, especially thermal stress, have resulted in tremendous economic losses for the dairy industry. Animals adapt to thermal stress by implementing various mechanisms to reduce heat production and enhance heat dissipation, such as increased respiration rate, sweating, elevated core body temperature, and reduced dry matter intake[1]. These coping mechanisms alter the physiological and biochemical processes within the animal’s body, including their immunity and microbiota composition[2], which further impact their productivity.
Reduced feed intake due to heat stress is often associated with negative energy balance, body weight loss, and high non-esterified fatty acid (NEFA) levels. However, research has shown that decreased feed intake only accounts for approximately 35% of the milk production decline caused by heat stress [3-5].
In the case of the UK, the average daily temperature is expected to rise by 4°Celsius by the end of the century, causing economic losses between £2000 and £6000 per year in average years and between £6000 and £14,000 per year in extreme years for average-sized dairy farms [9].
Under heat stress, dairy cows experience significant reductions in milk yield, milk fat, protein, and energy-corrected milk yields, as well as lower fat and protein concentrations. The average milk yield can drop by 2.2 kg among Friesian Holstein cows exposed to temperature-humidity index (THI) values of 65 or higher [6], and by 21% in a Mediterranean environment when the THI value increases from 68 to 78 [7]. Heat-stressed cows during the dry period also exhibit changes in postabsorptive metabolism leading to a subsequent reduction in milk production in the subsequent lactation period [8].
The physiological mechanisms underlying the impact of heat stress on dairy cows involve alterations in energy metabolism and the disruption of the hypothalamic-pituitary-endocrine axis, which regulates key functions like stress response and lactation. These changes can impair the mammary gland’s ability to use nutrients and produce milk. Milk yield (quantity) and milk components (quality) are highly related, but milk components are more sensitive to heat stress than milk yield [9].
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3 Replies
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The information is good
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Heat stress from climate change significantly impacts dairy production, causing roughly $40 billion in annual global losses by driving down milk yield and fertility.
While decreased feed intake causes some decline, roughly 65% of production loss stems from metabolic changes, including high nutrient demand for thermoregulation. The issue is acute in high-yielding cows, which have a lower tolerance threshold.
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