Article Sécurit'Lait Coopagri Bretagne - July 1996
Dry period: a crucial moment to address mastitis issues
The objectives of the dry period
The dry period allows the udder to rest physiologically. The cessation of lactation also means that nutrients can be used exclusively for calf growth and to replenish the cow's reserves.
Intramammary antibiotic treatment at dry-off has a dual objective:
The first is to eliminate udder infections responsible for subclinical mastitis at dry-off. These hidden udder infections result in high cell counts from calving onwards, and are more effective and less costly to cure outside lactation.
The second objective is to prevent new infections from setting in, especially during the first three weeks of drying off.
The essential rules for a good dry-off.
Reduce feed and stop concentrates 8 days before drying off.
Check that there is no clinical mastitis; only dry a healthy udder.
Dry off abruptly in one go (to limit infections).
Treat all cows with an intramammary antibiotic outside lactation (minimum duration of action 3 to 4 weeks).
Observe strict hygiene during treatment.
Isolate the cow from the milking environment.
Ration on the day of drying off.
Check the health of the udder in the days that follow (possibility of acute mastitis on drying off).
Feed during the dry period should :
- provide roughage,
- be balanced (UF, PDI, dry cow minerals),
- prevent the cow from losing weight,
- achieve a fat cover at calving of 3.5-4.
Target dry period: 50 to 70 days.
- Standard average dry period: 60 days,
- 50 days for a 4th lactation with a calving interval
- calving interval greater than 12 months.
- 70 days for a primiparous cow with more than 20 kg of milk less than 100 days before term.
Preparation for lactation
If the cow is isolated during the dry period, reintroduce her to the herd 2 to 3 weeks before calving to adapt to the herd hierarchy and make a dietary transition. For high-producing cows, add 1 to 2 kg of production concentrates 15 days before calving. In the case of milk fever, minerals can be stopped 15 days before calving.
Inhibitors
Intramammary medication at dry-off is the second most common cause of inhibitors, accounting for 31% of antibiotic residues found in milk. To avoid accidental delivery of milk from an animal that has dried off:
- identify dry cows (leg band, etc.) and isolate them,
- warn the replacement,
- avoid double drying off,
- in the event of premature calving, the milk withdrawal period is extended to 14 days (28 milkings),
- Don't use just any drying-off product. Depending on the pathological history of your farm, contact the vet responsible for applying the health programme on your farm.