Loss of BCS in early lactation
In early lactation, a cow does not reach peak intake until 10-12 weeks after calving, whereas, peak milk production occurs 6-8 weeks after calving.
To provide the energy necessary for milk production in early lactation a cow mobilises large amounts of body tissue (primarily fat, with small amounts of protein), which is reflected in a loss of body condition.
The greatest loss in body condition occurs in the first ten days after calving where cows can lose up to 0.5 BCS units. They continue to mobilise body reserves for approximately 8-10 weeks after calving, or until the point at which energy intake matches energy output.
Factors that affect BCS loss
Although increasing cow intake or reducing milking frequency post-calving takes several weeks before it has an effect on BCS, these management strategies can alter the point at which BCS loss ceases (nadir), and the rate of BCS gain after this point.
Cow genetics and BCS at calving have a stronger influence on BCS loss post-calving than nutrition or milking frequency during this period. The modern-day dairy cow is genetically predisposed to produce milk at the expense of body reserves during this period. In some cows, this can mean that 2-3 kg per day of body reserves are mobilised post-calving to support milk production.
Ideally, a cow should lose no more than 1 BCS unit from calving through to mating, with the aim to have all cows past the lowest point of energy balance and at a minimum BCS of 4.0 at the planned start of mating. This BCS profile will optimise milk production, while ensuring reproduction and animal health are not compromised.
Energy and nutrient requirements for early lactating cows
- See that latest Facts & Figures (p48-49) for information on how to calculate your herd's requirements.
- Alternatively, automatically calculate your herd's requirements with DairyNZ's FeedChecker.
- Determine Energy Requirements (FeedRight Technote 16)