Nutritional Factors Affecting Milk Composition

a) Level of feeding
Precalving: Increased feed intake in late pregnancy increases milk yield and the yields of fat and protein. The effects of condition score at calving on fat and protein percentage are small.
Post-calving: The effect of feeding level on fat and protein percentage is variable. This is because the stage of lactation influences the effect of feed intake on milk composition
If feed intake is increased during early lactation, milk yield will increase with consequent increases in fat and protein yields. As intake increases, the percentage of milk fat will decline, but protein percentage will increase slightly.
Protein production in well fed herds is rarely below 3.2 per cent, but in poorly fed herds it can fall to 2.8 per cent.

b) Diet quality
Pasture species influence milk yield and composition. The use of species associated with improved pasture quality results in increased milk, fat and protein yields.

The increase in fat yield is caused by an increase in milk yield only, since the percentage of milk fat actually declines. Increases in both milk yield and percentage protein cause the increase in protein yield.
c) Concentrates
Providing supplementary feed in the form of cereal grain usually results in increased milk, fat and protein yields. An increase in milk yield causes the increase in fat yield, since the percentage of milk fat often declines. Increases in both milk yield and protein percentage cause the increase in protein yield.
Feeding lupins also results in increases in milk fat and protein yields. Unlike the cereal grains, lupins do not reduce the fat percentage when they are fed as a supplement to cattle.
The cow generally uses protein supplements as a source of energy rather than a supply of protein to the udder. Providing there is sufficient protein in the total diet, feeding protein supplements will result in a similar increase in protein percentage as feeding a similar amount of energy from cereal grain.
If the protein content of the total diet is low, feeding protein supplements increases the energy content of the total diet by increasing the digestibility of the total diet. As a result, the protein percentage of the milk is increased.
Milk production and milk protein content will increase when an energy deficiency is corrected.
When concentrates are fed, the degree of processing can affect the fat percentage of the milk. Grains need only be cracked to allow sufficient digestion. Over-processing can reduce the fat percentage of the milk.
d) Fibre
If the milk fat percentage has dropped, but the protein percentage has remained constant, more fibre is needed in the total diet. This is best provided by feeding hay. However, cattle need only small quantities of hay (2 to 3 kg/cow/day) when they are grazing good quality pasture.

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Titany answered the question on April 22, 2022 at 09:06