Factors affecting milk composition

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Influences water, fat, protein, lactose and minerals

Diet alone may alter fat up to 3 % and protein 0.6%

• Yield, composition and properties of milk are not constant. A number of factors influence them
• Milk fat% of is the most variable constituent than any others
• Considerable variation occurs in protein% too but less than fat; Range of variation in lactose and ash content of milk is fairly low
• These all variations in milk composition are largely QUANTITATIVE

So,

• Results in variation in food value and economic value of milk

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Factor affecting the milk composition

1. Breed
2. Species
3. Genetic differences
4. Individual variations
5. Pregnancy
6. Age/Parity
7. Milking interval
8. Milking frequency
9. Stage of lactation
10. During Milking
11. Dry period
12. Season
13. Ambient temperature
14. Nutrition
15. Effect of hormone
16. Diseases
17. Feed and water supply

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1. Breed

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Milk composition of 5 breeds of dairy cattle

• Breed affects the size of fat globules
• Jersey produces milk with the largest fat globules while it is the smallest in HF milk

• Jersey milk has more volatile fatty acids than others
• Local, Jersey and Guernsey milk is deep yellow in color but HF milk has very less pigmentation

Highest production record

Breed: Girolando (a cross of HF and Gir)

Location: Sao Paulo, Brazil

Date: August 3, 2019

Milk produced: 123.61 liters

SUPER COW: 1.7 ton/lactation

���������Milk composition in different species

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2. Species

3. Genetic Differences

• It is uncommon to find two cows in same herd producing same yield with same composition
• Generally a cow can secrete milk upto 8% of their body weight
• Heritability is the proportion of variation in a population trait that can be attributed to inherited genetic factors. Heritability estimates range from 0 to 1 and are often expressed as a percentage. A number close to 1 may be indicative of a highly heritable trait within a population
• Heritability of fat, protein, and lactose content 0.58, 0.49, and 0.50, respectively, while that of milk yield average 0.27

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Animal selection matters

4. Individuality

Among Jersey cows …composition vary

• Heredity
• Environmental and physiological factor

Milk yield and composition more or less in different day

5. Pregnancy

• Pregnancy has an inhibitory effect on milk yield
• Reduction in milk yield occurs after 5^th month of pregnancy and by the 8^th month, milk yield declines sharply
• Increase in Estrogen and Progesterone level as pregnancy progresses, inhibits milk secretion
• Progesterone inhibits the activity of prolactin and α-lactalbumin

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During pregnancy, Estrogen and Progesterone inhibit milk secretion by blocking the release of prolactin from the pituitary gland and by making the mammary gland cells unresponsive to this pituitary hormone

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Changes in milk yield and progesterone in pregnant and non- pregnant cows after in semination

6. Age/Parity

• Milk production increases with number of lactation and is maximized in the 5^th or 6^th parity
• Increase body size and udder size
• While milk fat content remains relatively constant, milk protein content gradually decreases with advancing age
• 30% increase in milk production from the 1^st to the 5^th lactation
• After 6^th lactation milk production decline

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Comparative effect of parity on milk yield for Red Dane and Jersey cattle

7.Milking interval

• Normal milking interval is 12 hours
• Morning and evening milking vary milk composition
• Cows milking at unequal intervals produce less milk than those milking at equal intervals
• Incomplete milking for several consecutive days can permanently reduce milk yield for the entire lactation

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7. Milking interval………

• Single milking at 24 hours- loss milk production potential
• Milking time for most cows is 5-7 minutes per cow/role of oxytocin
• Residual milk in udder reduce both milk yield and fat content
• Each hour milking interval exceeds from normal milking hour, fat% reduced 0.1-0.15%
• Each hour milking interval below the normal milking hour fat% increase by 0.2-0.25%

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8. Milking frequency

• Milking twice a day yields at least 40% more milk than once a day
• Increasing milking frequency to 3 × day increases milk yield by up to 20% (range 5-20%)
• Shorter milking interval results in higher fat content, so milking thrice a day for entire lactation than twice a day increase milk fat% 10-20%

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Reasons ?

Milk composition vary due to milking interval and frequency

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Increased milk production

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Effect of milking frequency during the first week of lactation on daily milk production over the first 14 weeks of lactation

Milk production was lower during week 1 and tended to be lower during weeks 2 to 14 in cows milked once daily

■ = cows milked once daily during the first week of lactation and then twice daily for the rest of lactation

□ = cows milked twice daily throughout lactation

9. Stage of Lactation

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Changes in milk composition at successive milking (Colostrums phase)

9. Stage of Lactation ..contd……�Peak milk yield, protein and fat declines and lactose highest

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Changes in the concentrations of fat, protein and lactose over a lactation of a cow

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10. Change in milk composition during milking

• First drawn milk may contain only 1-2% fat
• At the stripping or end of milking, fat % may be 5-10%
• Tendency of the fat globules to cluster and be trapped in the alveoli against gravity

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Why?

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Evolution of milk fat content during milking in dairy cows 

11. Dry period

• Dairy cows are usually dried-off for two months prior to the next calving
• Milk yield is usually reduced when the dry period is less than 40-60 days (25-40% less milk)
• Dry period longer than 60 days in length does not result in a significant increase in milk production
• Long dry periods decrease the average annual production………….
• For good physical and physiological condition or repair of wear and tears

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��������������11. Seasonal Variations

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Fat yield

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0.2-0.4%

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Effect of season on fat % in cow milk

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Aug- Feb

Why fat% is lower during Aug- Feb in cows?

• Milk production in Nepal peaks during August–February and significantly drops during March–July
• Primarily due to the availability of green fodder, which is abundant during the monsoon and spring but scarce in the dry, late summer and winter months
• The ratio of lean to flush season milk production is roughly 40:60 for cows and 35:65 for buffaloes.

12. Seasonal Variations

• Total milk yield increase 10-20% in winter
• Milk fat and protein percentages are higher by 0.2-0.4% in summer than winter
• Linked with available pasture quality and total volume of milk produced
• Cows calving in the fall or winter produce more fat and solid-not-fat than cows calving in the spring and summer, why????
• Because, microbial digestion is low in summer calvers due to low coarse pasture during peak production leading to lower milk fat

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13. Ambient temperature

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• Breed specific effect
• Holstein tolerates low temperature and local/Small breed tolerates higher temperature
• Milk fat and SNF increase with decreased temperature
• Holstein ..optimum temp 10^°C and above 27 ^°C production and milk quality hampers
• High temperature ---- drop in feed intake, more water intake, increase respiration rate, decrease milk yield and quality

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High stress

14. Effects of nutrition on milk composition

• Milk fat is the most influenced constituent by dietary manipulations
• Plane of nutrition
• Forage concentrate ratio
• Forage particle size (forage processing)
• Ruminal acetate propionate ratio

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Maximizing rumen function can increase milk components

14.1 Plane of nutrition

• Underfeeding dairy cows reduces lactose % and increases fat %
• Feeding imbalance rations (e.g. low energy: protein ratio) may reduce milk fat and protein percentages
• High producing cows should eat 3.5 - 4.0 % DM of their body weight daily

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NEB in high yielders

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Quick facts

• The transition period is 60 days before calving and 30 days after calving
• NEB occurs after calving when a cow is using more calories than she is eating
• Reducing the time spent in a NEB by encouraging feed intake is the most important goal of transitional cow management

14.2 Forage: Concentrate ratio

• To maintain normal milk fat%, forage concentrate ratio should be approximately 60 to 40
• Acetate:Propionate:Butyrate= 60:20:20

* Acetic acid dominates (60%), lipogenic VFA so yields higher milk fat

• If changes in ration, results in decreased rumen pH, increased propionic acid production and poor fiber digestion

* Increase concentrate in the ration leads to decline in fat %, due to alteration in acetate: propionate: butyrate

• If the concentrates are fed separately from the forage, fat % decline (Reduced ruminal acetate: propionate ratio)

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14.3 Forage particle size (forage processing)

• Feeding finely chopped forages has a negative effect on milk fat %
• Finely chopped forages spend less time chewing and therefore will produce less saliva
• Ruminal pH will drop as there is less saliva
• As the ruminal pH drops below 6, cellulolytic bacteria is reduced, then less production of acetic and butyric acids
• Ideal particle size depends on the forage, but as a general rule, BMR corn silage should be chopped at ⅜- to ¾-inch

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So what is the correct forage particle size? There is no one answer that fits all dairy operations. The bottom line is to find what works on ones farm to optimize rumen health and milk output

117- 183 L/d

15. Diseases

• Infection of the udder (mastitis) greatly influences milk composition
• Concentrations of fat, SNF, lactose, casein, b-lactogolbulin and a-lactalbumin are lowered while concentrations of blood serum albumin, immunoglobulins, sodium and chloride ions are increased
• Casein content may be below the normal limit of 78% and chloride ion increase to 0.12%
• Electrical conductivity of normal milk range from 4.6 to 5.8 mS/cm; and somatic cell count (SCC) must not exceed 250, 000/ml milk
• Increased in EC and SCC of milk can be used as the proxy indicator of mastitis

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16. Effect of Hormone

Growth hormones (BST)

• Positive correlation with milk production of cows
• Growth hormone causes redistribution of nutrient within the cow’s body and favor nutrient utilization for milk production

Prolactin: Maintenance of lactation

Thyroxin: Iodine containing hormone, increase milk fat, TS and Milk yield

Oxytocin: milk letdown and increase milk yield

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17. Feed and water supply

• Any restriction in feed or water supply will result in a drop in milk production
• Insufficient supply of water for few hours will result in a rapid drop in milk yield
• As the level of starch in ration increases, the level of propionate produced in rumen is increased while that of acetate is decreased and this causes a reduction in fat %
• Incorporation of fat or oil in dairy cow ration can substantially alter profile of milk fatty acids

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Feeding management practices and their potential impact on milk fat and protein concentration

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Summary �

• Many factors can influence milk composition
• Certainly, genetics plays an important role, but changes here are slow
• Keep disease to a minimum and adjust their management program as the seasons permits
• Best play- Take advantage of nutrition OPTIMIZATION that maximize rumen function

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