DairyCo

Nutrition & Milk Production

Most of the major constituents of milk - lactose, fat and protein - are synthesised in the mammary gland from precursors selectively absorbed from the blood and transported either from the digestive system or from body reserves. Since the amount of water secreted by the mammary gland is directly related to lactose levels, lactose synthesis is the principal driver of milk volume. The primary building blocks of milk fat are the VFAs, acetate and butyrate, with glucose supplying the glycerol required. Milk protein - primarily casein - is produced from amino acids. 

Influencing Milk Components

The levels and ratios of individual VFAs produced by the digestive system can have a marked influence on milk fat and protein percentages.

There are a number of ways of manipulating milk solids levels through feeding, although the cost-effectiveness of ration adjustments always needs to be assessed against the specific milk contract. 

Milk protein percentages can best be increased by:

• Increasing the energy density of the ration.
• Feeding high ME silages with good intake potential.
• Increasing the protein content of the ration.
• Feeding mixed forages.
• Increasing the degradable starch content of the ration with ingredients like rolled wheat.
• Increasing the by-pass starch content of the ration with ingredients like crimped maize.
• Increasing the by-pass protein of the ration with ingredients like protected soybean meal.
• Using both protected starch and protein.
• Feeding protected methionine.
• Avoiding added fat (even protected fat).
• Calving cows in optimum condition. 

Milk fat percentages can best be increased by:

• Increasing the forage to concentrate ratio.
• Feeding high fibre forages.
• Sufficient long fibre.
• Feeding high digestible fibre concentrates.
• Feeding concentrates little and often to stabilise rumen pH.
• Avoiding high oil by-products like distillers and brewers grains.
• Avoiding whole oil seeds like full fat soya and whole rape seed.
• Avoiding fish oil products and/or Feeding small amounts of a protected fat.

Protected Fats

Fats are protected from rumen degradation either by conversion into a rumen insoluble soap or naturally by virtue of a high melting point which makes them relatively inert in the rumen. The form of protection must, of course, ensure they are available for breakdown and absorption lower down the digestive tract.

The fatty acids making up protected fats can be a relatively pure source of 16 carbon chain molecules - palmitic acid (known as C16s) - or a mixture of C14, C16 and C18 molecules (usually referred to generically as protected fats). C16 fatty acids can be directly converted into milk fat to boost butterfat percentages.