Factsheet: Transition Slide Advisory

The transition slide is a tool to help monitor the metabolism of energy, protein, and minerals during the transition period. Key focus areas include preventing (subclinical) ketosis and hypocalcemia. The animals to be monitored are "close-up cows" (20 to 2 days before calving, ideally 5–10 days before) and fresh cows (1 to 10 days after calving, ideally 3–4 days after).

The transition phase can be divided into three periods, each requiring separate assessment (although each is influenced by the previous one):

1. Close-up group
2. Calving pen
3. Fresh lactation group 

A key factor during the transition period is total dry matter intake (DMI). Aim to maximize DMI (visible from rumen fill) without supplying excessive energy, protein, or minerals. Always first evaluate general management before changing the ration.

Factors influencing DMI:

1. Feed – Always ensure feed availability and palatability.
2. Drinking water – Ample, clean, easily accessible, multiple points, long troughs preferred.
3. Stocking density – All cows should be able to eat and lie down at the same time.
4. Lying beds – Spacious, clean, and soft.
5. Space to move – much space, no dead-end alleys, preferably with an outdoor space.
6. Climate – Ensure adequate ventilation to prevent heat stress.
7. Low stress – Minimize group changes and avoid isolating cows in the calving pen.

Only once these management factors are optimized, is it useful to focus on ration adjustments.

Start by evaluating NEFA levels before calving (reference: 0.1–0.4 mmol/L; target: 0.1 mmol/L). Elevated NEFA levels (problematic if multiple cows are between 0.25–0.4 mmol/L) warrant checking:

1. Body condition of close-up cows (scores ≥ 3.5 reduce DMI earlier and more before calving).
2. Feed availability (is there always feed in the trough? overcrowding?).
3. Ration composition (low in energy/protein can impair rumen function).

If NEFAs are elevated after calving but not before, assess calving management:

• Is enough feed and water always available?
• is stress minimized (e.g., through isolation from the herd)?

After calving, some fat breakdown is normal. NEFA reference: <0.6 mmol/L; target: <0.4 mmol/L. If fat breakdown is excessive, recheck the earlier periods.

BHB (used only post-calving) indicates actual ketosis. If BHB >1.2 mmol/L and the cow is producing less milk or shows other signs (less rumination, reduced intake), treat with an energy source like propylene glycol.

Prepartum BHB is only relevant for butyrate formation in the rumen, which is not clinically significant.

BUN (blood urea nitrogen) measures circulating urea, a waste product from protein breakdown in the rumen when there's excess protein relative to energy.

• Pre-calving reference: 3.3–6.6 mmol/L. Adequate protein supports good colostrum, rumen activity, and udder development. Excess is inefficient and possibly harmful.
• Post-calving: BUN levels correspond to milk urea (3.3 mmol/L BUN ≈ 20 mg/L milk urea). Ideal post-calving BUN is 3.0–3.3 mmol/L in the Netherlands.

Note: BUN only reflects rumen degradable protein. To assess total protein intake, also measure Albumin and Total Protein (via the Nutri Balance slide).

These minerals are essential to prevent hypocalcemia (subclinical milk fever), which occurs if calcium drops below 2.15 mmol/L after calving.
Measure calcium on day 3 or 4 post-calving, unless clinical signs appear earlier.

If hypocalcemia is found in fresh cows, take the following steps:

1. Check DMI (see above). Fluctuating magnesium levels in close-up cows suggest inconsistent DMI. Ideally, Mg variation between cows should be <0.2.
2. Check Mg levels in close-up cows – should be ≥1.0 mmol/L. Can be corrected immediately via the ration.
3. Check P levels – ideal is ~1.5 mmol/L. If average exceeds 2.0 mmol/L, reduce by switching to low-phosphorus feeds (e.g., corn silage instead of grass silage, soybean meal instead of rapeseed).
4. Evaluate bone mobilization before calving. Ca levels around 2.4 mmol/L in close-up cows indicate adequate activation. Lower values may require dietary adjustments, such as reducing DCAD (dietary cation-anion difference) or using phosphorus binders. Ensure sufficient vitamin D in the ration as well.