Effective measures to improve milk quality in summer

Improving milk quality can increase the income of dairy cow profit. every 0.1 unit increase of milk fat will increase unit price of milk by ￥0.02/kg. every 0.1 unit increase of milk protein will increase milk unit price by ￥0.05/kg. As a contrast, every decrease of milk fat or protein will result in the decrease of unit price or even rejection.

In summer, decrease of milk quality is a common problem. When environment temperature and humidity index (THI) exceed 68, dairy cows will be in a state of heat stress, during which feed intake will decrease, digestion and metabolism will be disordered, and milk quality, including milk fat and milk protein rate, decrease.

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The negative balance of energy caused by heat stress is the main reason for the decrease of milk quality

• Under heat stress, dry matter intake (DMI) of dairy cow will decrease 2-14 kg

Under heat stress, lactating cows usually first choose to reduce DMI to reduce their own body heat production (Baumgard and Rhoads, 2013).

Mechanism: under heat stress, the peripheral blood flow increases, which increase the heat dissipation and lead to the slow down of rumen peristalsis, chyme emptying speed and inhibit the feed intake.

• Heat stress increases nutrients needs by 7% - 25%

Cows under heat stress will stand more to dissipate heat, resulting a reduction of lying time by 30% (Allen, 2015; Polsky, 2017). Prolonged standing time increases energy expenditure (West, 2003), and reduces breast blood flow and nutrient supply (Rulquin, 1992; Delamaire, 2006). The amount of amino acids involved in the synthesis of glucose by gluconeogenesis in the blood will increase (Wheelock, 2010), resulting a further decrease in the total amount of amino acids entering the mammary gland and an increase in milk urea nitrogen (Cowley, 2015).

Note: DMI decreases under heat stress while nutrient requirements increase leads to negative energy balance of dairy cows and lower the milk quality!

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Conventional measures to relieve heat stress in dairy cows have limited effect

• Measures 1. Improve environment

When environment temperature, 5-20 ℃ is the best, and humidity index (THI) exceeds 68, dairy cows are in heat stress state. In summer, through physical cooling, temperature and humidity of the ranch barn still exceed 68. High yielding cows are more sensitive to the environment. When milk production increases from 35 to 45 kg per day, the temperature threshold for heat stress in dairy cow should be 5 ℃ lower (Berman, 2005).

(spray cool water + fan, cows still pant)

• Measure 2. Adjust diet

In summer, it is a common measure to increase the nutrient concentration by the ratio of concentrate feed to forages of the diet to compensate for the insufficient nutrient intake caused by the reduced feed intake. However, there're unavoidable risks at the same time:

Acidosis. Hight ratio of concentrate feed will lead to a rapid decrease in rumen pH. Low coarse materials will lead to a decrease in ruminating time and saliva secretion, which is more prone to acidosis.

More decrease of feed intake. Low rumen pH will lead to a decrease in dietary fiber digestibility, a slower rumen empty rate, and a continuous filling state in the rumen, which inhibits feed intake.

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Traditional methods have limited alleviation of heat stress. Is there an other coup?

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Enhancing the rumen fermentation of dairy cow is an effective measure to solve the decline in milk quality of dairy cows in summer!

Benefit 1. Increase feed intake

The digestion of roughage completely dependent on the function of rumen fermentation. For every 1% increase in the roughage NDF digestibility, the DMI of dairy cows will increase by 0.16 kg per day (Akbar, 2014).

Benefit 2. Increase MCP, VFA production to supply more raw materials for synthesis of milk protein and milk fat

When rumen MCP production increase 20%, milk protein will increase 0.2% (Zhao Meng, 2015)

When rumen VFA production increase 20%, milk fat will increase 0.4% (U Dandan, 2016)

Peptides works!

• Peptides enhance proliferation of rumen microbes

As the first nitrogen source for rumen microbes, peptides can shorten the cell division cycle of rumen microbes and increase the efficiency of microbial proliferation (Hoover, 1991; Griwold, 1996; Fu, 2001).

Jiangxi Agricutural University & Modern faming Co. & Mytech Co.

Sichuan Agricutural University & Newhope Dairy Co. & Mytech Co.

• Peptides enhance rumen digestion

• Peptides increases production of MCP, VFA

Adding a certain amount of peptides to the rumen fluid can promote synthesize of MCP of about 15% through increasing use of ammonia nitrogen by rumen microbes (result of research project in Mytech).

Adding a certain amount of small peptides to the rumen fluid can promote rumen microbial degradation of diets and increase VFA production by about 15% (result of research project in Mytech).

• Peptides improve milk quality, increase milk yield