Health Management Practices for Dry Dairy Cows

Introduction
Dairy cows require a rest period between lactations. The udder and the digestive tract especially benefit from rest during the dry period. The dry period is actually the beginning of the next lactation. It is the best time to institute management practices to prevent health problems and to ensure good production in the lactation to follow. This Factsheet describes practices which aim to promote good health and performance in early lactation cows.

Drying-Off
Drying-off occurs when milk is left in the udder for 18 hours or more. The resulting pressure causes the milk glands to stop producing droplets of milk. This eventually leads to reduction in the size of the udder.

The standard recommendation has been to withdraw concentrates from the cow's ration for about one week and then abruptly stop milking. Moving late lactation cows to a different stall or loose pen and restricting water intake reduces milk production. Cows which are producing in excess of 25 kg of milk per day are difficult to dry off abruptly and may be more susceptible to new intramammary infection.

Recent research suggests removing the concentrate ration for 7 to 14 days accompanied by once a day milking may be a good way to dry off cows. Cows dried off in this manner developed fewer new mastitis infections than cows which were dried off abruptly without a change of ration.(1)

Cows should have a dry period of about 60 days. During this time they should be separated from lactating cows and grouped according to early dry period and close-up to calving. This grouping is to facilitate nutritional management. Dry cows should be housed in clean, dry, comfortable loose pens or paddocks. Exercise is important to maintain normal body functions and muscle tone.

Early Dry Period
The early dry period comprises the first 4-5 weeks after drying off. During this period attention should be given to mastitis prevention, vitamin supplementation and body condition.

Mastitis Prevention
Dry cow intramammary antibiotic treatment is necessary to prevent new udder infections in the early dry period. It also eliminates sub-clinical infections persisting from the previous lactation. Selection of an infusion product should be based on your veterinarian's advice as well as the antibiotic sensitivity patterns for known mastitis agents in the herd.

Two standard recommendations should be noted. Immediately after the last milking, infuse all 4 quarters of each cow with the appropriate intramammary slow release antibiotic preparation. Before treatment, prepare teat ends aseptically with teat dip and alcohol swabs. This prevents environmental mastitis bacteria from being accidentally introduced into the teat on the infusion cannula.

Vitamin Supplementation
Cows in late pregnancy have a high requirement for vitamins A, D, E and selenium.

Vitamin A is known to prevent premature, weak and stillborn calves and retained placenta. Providing vitamin A orally in a commercial dry cow premix (100,000 IU/day) or by intramuscular injection at drying-off prevents any deficiencies.

Vitamin E and selenium supplementation are necessary to enhance the body defences to protect the cow from challenge by infectious agents. Recommended levels for confined Holstein cows in areas of known selenium deficiency are vitamin E, 1000 IU/day and selenium, 3 mg/day during the dry period.(2) This is best administered by inclusion in the ration.

Dry cow rations should be evaluated and balanced to provide correct amounts of vitamins A,D,E and selenium

Body Condition
Early lactation cows have a high energy requirement for milk production and reproduction. They also have a reduced dry matter intake (DMI) for the first 60 to 70 days in milk. During this period they must utilize stored body fat as a source of reserve energy.

Body condition scores indicate the amount of stored energy available to the cow. In early lactation one kg of body fat provides the energy needed for 7 kg of milk. Lactating cows will utilize about 1 kg of stored fat daily in order to meet their energy requirements. If cows utilize more than 1 kg/day especially in the first 14 days in milk, fatty degeneration of the liver is excessive. As a result ketosis may occur and the interval to conception will be prolonged.

Cows gain condition most efficiently during late lactation. Ideally cows at dry-off time should have a body score of 3.5-4. No weight loss or gain in condition should occur during the dry period unless needed. Dry cow rations should be evaluated and balanced to meet daily protein and Total Digestible Nutrients (TDN) requirements. National Research Council 1989 recommends 1.35 kg crude protein and 6.3 kg TDN daily for a 700 kg dry cow.

Close-up Dry Cows
The close-up dry period comprises the 2 to 3 weeks prior to calving. During this time lead feeding, milk fever prevention and maternity facilities must be emphasized.

Lead Feeding
In late pregnancy the enlarging uterus occupies more of the abdominal cavity. This reduces the rumen's capacity for feed. Late pregnancy cows have a limited DMI of about 2% of body weight (BW) daily. At this time a good roughage base must be established. Preferably this should consist of about 12 kg of corn silage and free choice hay. Lactating cow grain ration can then be gradually increased to 4-5 kg/day by calving day. Lead feeding of grain ration starting 2 weeks prior to calving helps to avoid digestive upsets resulting from abrupt changes from pre- to post-calving rations.

After calving, increase grain gradually (maximum 1 kg/day) as production increases and appetite increases. Increase the protein supplement first to stimulate milk production and the grain ration second. During lactation the concentrate to roughage ratio on a dry matter basis should not exceed 60:40. Feeding programs and total mixed rations (TMR) which exceed this ratio run the risk of predisposing cows to abomasal displacement, laminitis and off-feed problems.

Introducing close-up dry cows to a lactating cow TMR is a form of lead feeding. If possible, the dry cows should receive a low calcium TMR formulated for low production cows for no longer than 5 days before calving. A longer introductory period could predispose mature cows to milk fever.

Milk Fever Prevention

Calcium
A dairy cow's requirement for blood calcium increases suddenly with the onset of calving and during early lactation. When calcium levels in blood are too low, cows may develop milk fever at calving time. In addition, their appetite and muscle tone will be poor during the first two weeks of lactation. Good muscle tone improves the function of the digestive tract and also assists the involution of the uterus. Good appetite increases DMI and milk production and helps to prevent ketosis.

A cow in early lactation milking 40 litres/day requires about 56 grams of blood level calcium daily from her diet and bone storage reserves.

A cow's DMI is limited during early lactation. Therefore, it is difficult for the cow to obtain enough calcium from the diet to meet requirements. For optimum health and performance, dairy cows need to draw on reserve calcium which is stored in their bones.

If the cow is stimulated to release reserve calcium from bone, 10-15 grams daily is available (Figure 1). This amounts to 20-25% of the daily requirement for blood level calcium. However, it takes about 14 days to condition a release of stored calcium into the blood from bone. It is essential to start this conditioning at least two weeks before calving by feeding close-up dry cows less than 100 grams of dietary calcium/day (70 grams/day for small breeds). This feeding strategy stimulates the cow to begin mobilizing reserve calcium prior to calving.

Figure 1. Calcium Removal from Bone in Early Lactation. The 10-15 g of reserve calcium available in early lactation is especially important because it is cell level calcium. A fresh cow needs 56 g of cell level calcium per day for 40 kg milk production.

Health Management Practices for Dry Dairy Cows - Image 1

Health Management Practices for Dry Dairy Cows - Image 1

The addition of anionic salts to the close-up dry cow grain ration will also stimulate the release of reserve calcium from bone. Ammonium chloride and magnesium sulphate are examples of anionic salts. Most feed companies have a dry cow supplement containing anionic salts. However, anionic salts are somewhat unpalatable, so they must be thoroughly mixed with grain or a TMR and the dose divided into 2 daily feedings. Anionic salts should not be fed for more than 3 to 4 weeks.

Magnesium
A high incidence of milk fever has been reported in dairy herds with an insufficient supply of magnesium during the dry period.⁽³⁾ Cows deficient in magnesium had low rates of calcium mobilization compared to cows which received sufficient magnesium. Milk fever prevention includes balancing dry cow rations for calcium, phosphorous and magnesium. The following levels are recommended: calcium 0.39%, phosphorous 0.24%, and magnesium 0.23% in the total diet.

Free choice mineral feeding may result in mineral imbalance. As an example, excess phosphorous may interfere with Vitamin D metabolism and cause milk fever. Minerals should be fed in measured amounts daily.

Udder Edema Prevention
Dry cows should be offered cobalt iodized salt at the rate of 30-40 grams/day. Excess sodium which comes from salt can cause udder edema in dry and springing cows.

Maternity Pens
Maternity pens should be clean, comfortable and provide good footing. Third lactation and older cows are most susceptible to milk fever and related post-calving complications such as retained placenta, slow uterine involution, poor appetite, and ketosis. Placing dry cows in a maternity pen or calving paddock for two weeks before calving is a good way to control the diet to prevent metabolic problems. If a cow develops milk fever in a clean comfortable maternity pen, complications such as mastitis and muscle damage are less likely to occur and treatment will be easier.

Calving facilities must be dry and clean to prevent infectious diseases such as mastitis, retained placenta, infection of the uterus and calf scours.

Summary
The dry cow management procedures described in this Factsheet are intended to:

Prevent and eliminate mastitis by proper drying-off procedure, dry cow treatment and clean dry comfortable housing.
Strengthen the cows' immune systems and body defences by ration balancing and supplementation of vitamins A, D, E and selenium.
Ensure sufficient body condition to provide reserve energy to meet requirements for milk production and reproduction in early lactation.
Prevent digestive upsets and displaced abomasums by proper forage feeding and lead feeding grain to the closeup dry cows.
Prevent milk fever by restricting dietary calcium for the last 2 to 3 weeks of the dry period and/or feeding anionic salts to stimulate the release of stored calcium from bone at calving time.
Stimulate and maintain aggressive appetite during the dry period and early lactation to ensure maximum DMI, good rumen-fill, normal utilization of stored fat and high milk production.
Prevent udder edema by proper sodium intake and exercise.
Prevent calving injury, retained placenta, infection of the uterus, mastitis and calf scours by providing a clean dry maternity pen with good footing.

References

1.- Oliver, S.P., et al. Influence of Different Methods of Milk Cessation on Intramammary Infections During the Peripartum Period. Proceedings of International Symposium on Bovine Mastitis, 1990; 92-97.
2.- Smith, L., et al. Vitamin E and Selenium Can Help Lower the Incidence of Mastitis. Large Animal Veterinarian, November/December 1988.
3.- Van Mosel, M., et al. Effects of Deficient Magnesium Supply During the Dry period on Bone Turnover of Dairy Cows at Parturition. The Veterinary Quarterly, Vol. 13, No.4, October 1991; 199-207.

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