11 September 2010

9 minute read

Entry and preparation of the cow

Mr Swinkels says that dried off cows should have a body condition score within a range of 2.5-3.

"It is important that there is a focus on nutritional management towards the second half of lactation, so that cows achieve the ideal body condition score for a dry cow."

He warned that there are various body condition scoring systems worldwide, and advises producers to check the most common system per country and verify the norms.

Drying off

The dry cow period starts with an abrupt cessation of milking and the insertion of dry cow treatment. Milk production should be as low as possible.

Low milk production at drying off ensures a minimal build up of milk pressure in the udder and consequently a lower risk of milk leaking, meaning effective closure of the teat canal so reducing the chances of infection.

The risk of mastitis shortly after drying off is relatively high, especially if dry cow treatment is eliminated due to leaking.

Mr Swinkels says that cows to be dried off should be are gathered into a separate group that receive a low-nutrient ration to reduce daily milk production (under 15 kg/35 pounds/).

Once milking is stopped, teats must be cleaned and dry cow treatment applied immediately.

Mr Swinkels says that depriving cows of water and feed at the beginning of the dry cow period is stressful and unnecessary.

Recharging the rumen

The rumen is vital to milk production and cow health. Free fatty acids that are produced and, for the most part absorbed in the rumen can supply up to 80 per cent of the cow’s energy needs.

A substantial proportion of dairy cows experience an incidence of subclinical ruminal acidosis during lactation. Figures in studies vary from 19 to 50 per cent of cows.

For a healthy and productive rumen, it is essential that the rumen pH remains between 6.0 and 6.5. Subclinical ruminal acidosis (SARA) arises when the rumen pH decreases into a zone that is suboptimal for ruminal function (pH 5.2 to 6.0).

Mr Swinkels says that high acidity irritates the rumen and damages the ruminal epithelium, destroying absorptive capacity and immunological barrier function.

To recover and renew it’s epithelium (surface that absorbs minerals etc.), the rumen needs a ration that is high in fibre and low in rapidly degradable carbohydrates, advises Mr Swinkel.

Typically this is a ration that is fed in the dry period, as the energy needs of the cow are relatively low in this period. To ensure that the cows really eat this ration, selective eating should not be possible and the cows should eat relatively small volumes of feed (10 to 14 meals per day, on average) at frequent intervals.

Mr Swinkel recommends that the farm's nutritionist formulates an effective dry cow ration, which is fed once or twice a day.

Recharging udder health

From the standpoint of udder physiology, the dry period can be divided into 3 stages:

Active involution: This is the first two weeks after drying off, milk is absorbed, immunity suppressed and passive immunity installed.

Daily production peaks at day 4. There is a high risk of intramammary infections and mastitis during the involution stage, for several reasons:

1. The innate immune system is poorly established, because of:
   
   
   • the immune function of leukocytes in milk in general is impaired, due to the absence of complement factors, immune factors and glucose. Complement factors and immune factors support killing and phagocytosis of bacteria;
   • there is a low concentration of leukocytes in the milk, and their activity is impaired by phagocytosis of fat, casein and cell debris as part of the process of absorbing the accumulated milk by the udder;
   • high citrate levels block the protective effect of lactoferrin. Lactoferrin binds iron-ions, thus inhibiting the growth of bacteria.
   
   
   
2. The physical barriers for bacteria entering the teat canal are not yet effective. An effective keratin plug is not yet established and there is no flushing out of infections with the milk stream during milking. What’s more, the steady build up of milk pressure contributes to milk leakage.
   
   
3. Depending on the management, the cow can be stressed due to regrouping, changing of daily routines, feed deprivation and a new environment. High cortisone levels as a result of stress impair the immune system.

Steady state: During this state, there is no involution, no milk production and the milk secreting epithelial cells renew.

This is the period with the highest immunity against intramammary infections.

Colostrum formation: This period usually lasts +/- 2 weeks before calving, and is identifiable by the secretion of milk/ colostrum.

Towards the calving date, milk pressure builds up, putting pressure on the keratin plug and causing milk leakage. The cow usually is not milked in this period, so there is no wash out of bacteria in the teat cistern and teat canal.

Immunity starts to decrease around 15 days prior to calving, due to changed udder conditions and systemic effects.

Udder conditions leading to decreased immunity are related with lactoferrin and leukocytes. The activity of lactoferrin is reduced because the concentration goes down due to dilution and because citrate concentration goes up. Also the concentration of leukocytes decreases, together with a reduction in their phagocytic capacity caused by the presence of fat and casein.

Other factors such as changes in steroid hormone status, ketosis, a high BCS, milk fever, acidosis and deficiencies may also decrease immunity.

To maximise udder health, Mr Swinkel recommends the following:

Dry cow treatment: It is essential to use a dry cow treatment that fits with the length of the planned dry period. The treatment must be active against contagious pathogens and environmental pathogens. Towards the end of the dry period, the risk of infection from environmental pathogens increases.

Clean environment: Keep the environment clean, with special attention to mastitis pathogens. Mr Swinkel say that it is imperative that no cows with mastitis or high cell counts are brought into calving/fresh cow areas.

Use practical procedures for cleaning and disinfecting, such as using high volumes of clean bedding or calving on pasture, instead of washing and disinfecting between calvings, seem to be more effective in preventing mastitis, prolonged calving and scours in new born calves.

Minimise stress for the cow. Low stress and no stress housing systems for dry cows are a part of well-designed buildings.

Ensure there is enough individual space for the cow around calving with space for her to lie down, meaning loose housing with >9 m2/100 sq ft lying space per cow.

Limited access to feed, and fighting for feed can be very stressful for dry cows.

Good ration formulation and nutrition. Provide at least 1x per day the correct, palatable ration and remove refusals beforehand.

Recharging Milk Secretion Capacity

Studies have shown that milk production is highest after a longer dry period (60-days).

Milk is produced by epithelial cells in the alveolar structures in the udder. The number of epithelial cells and their milk secreting capacity seems to be the key to maximal milk production capacity. Like all cells, epithelial cells in the udder continuously die and renew themselves. Milk production capacity seems to be the result of the balance between dying and renewed cells. This balance is probably manipulated by hormones in the cow. After the peak milk production, the number of dying cells is somewhat larger and the number of replicating cells somewhat lower and as a result milk production declines towards the end of lactation. In a 60 day dry period, this process continues in the first 25 days of that dry period. However, in the remaining 35 days of the dry period, in the steady state, the balanced is tipped towards more cell renewal and less dying cells. In other words, especially during the steady state of the dry period, the udder replaces old milk secreting cells by new ones and those new ones are more able to produce milk during the adjacent lactation.

Mr Swinkel it is unknown how long epithelial cells live. However, it seems to be that it takes time for epithelial cells to grow old and to die and only then can they be replaced by new cells. Successful replication of epithelium cells needs time too. Therefore, it is likely that the dry period needs to be long enough to have time to replace old epithelial cells resulting in a high milk production in the next lactation.

Recharging Hoof Health

Hoof horn grows with a speed of 4-5 mm per month. The hoof sole is 7-12 mm thick. After a 60 day, (2 months) dry period the complete hoof sole will be renewed.

Around drying off , hooves should be checked, and trimmed and treated if necessary. Treatment of digital dermatitis often requires a second treatment. Solar ulcers will usually heal during a 60 day dry period.

The following is essential for recuperation of hooves during the dry period:

• adequate resting time: comfortable, dry and soft bedding both in cubicles and loose housing, no heat stress;
• dry and clean hooves: clean dry, walking surfaces, good ventilation;
• low infection pressure: treat infected hooves before or at drying off , no infected hooves within the dry cow group, scrapers should not bring manure from infected lactating cows to the dry cows;
• 2x daily inspection of every cow and immediate appropriate action when indicated.

Giving birth

The calving process itself does not have a direct bearing on udder health. Birth can lead to trauma in the uterus and vagina, which is painful and thus increases the risks of metritis, solar hemorrhages (longer standing time), and it reduces the feed intake (higher risk of ketosis, ruminal dysbacteriosis, displaced abomasum). All these factors can increase the risk for intramammary infections and mastitis.

Cow stress should be minimised as much as possible. Adequate and skilled assistance must be provided.

After calving

The drop in immunity around calving can last up to 3 weeks after parturition. At the same time there is a high risk of metabolic (ketosis) and ruminal problems (acidosis, dysbacteriosis). Secondary problems can further aggravate the situation including endometritis, acute laminitis and abomasal displacement. Cases of mastitis can be more severe and more difficult for the cow to recover from.

During this period, cows are extremely prone to infections, especially mastitis and endometritis. It is therefore important to:

1. minimise the exposure to udder pathogens;
2. limit the drop in immunity as much as possible.

Mr Swinkel recommends milking fresh cows before others, so as to avoid contamination, keep cows in clean and dry environment, use well maintained milking equipment, keep cows with infections seperate to others and apply post-milking teat disinfection.

He also says it is important to minimize stress for the cow, and optimise nutrients, vitamins, minerals and trace elements in ther diet.

Conclusion

A broad spectrum antibiotic dry cow therapy treating and protecting for 60 days should be part of any well-managed dry cow period. Best practices must include special attention to stress reduction, dry cow ration, cow comfort and the control of environmental pathogens.

These practices, along with the appropriate dry cow therapy applied across the herd, will enable cows to attain maximum health resulting in an optimal next lactation.