1999 April

Mad Cow Disease

Australia is in the enviable position of having not had Mad Cow Disease (also called Bovine Spongioform Encephalopathy or BSE) diagnosed in its cattle herd. BSE is spread by feeding infected offal or meat based products to cows. This practice has now been banned in Australia.

To maintain a "clear" status Australia's trading partners require us to show that we are regularly monitoring the status of our national herd for freedom from this disease. To do so we need to be testing animals that show any symptoms which may be indicative of the presence of BSE even though it has never been seen here (if you don't look for it, how do you know you don't have it).

The government has asked veterinarians to select animals for this monitoring program, which show one or more signs of diseases affecting the nervous system. This involves collecting blood samples and completing detailed submissions on their history and clinical signs. If these animals do not respond to normal treatment, the government is prepared to pay the farmer $150 to have the brain removed by a veterinarian. This is regardless of the confidence with which the attending veterinarian has diagnosed the clinical condition. Your help would be appreciated in bringing to our attention such animals.

How Long Does A Cow Need For Her Dry Period?

Gone are the days for many farmers where it is possible to dry off the whole herd for 2 months and have a break from milking. The tight financial situation for such farmers means that cows need to be producing as much milk in autumn as possible to help produce any profit for the year.

Apart from that reason, some farmers will choose to milk through because they can make more money during the high paying months of March to June. Building up a feed wedge for winter can still be achieved simply by slowing the rotation if necessary and continuing to feed supplements to the milkers such as silage hay and grain.

A cow still producing 18 litres in April will need about 6-8 kg dry matter more than she would if dry. If this were all as grain, it would cost an additional $1.20 in feed costs per day to keep her milking. At 30c/litre x 18 litres this is $5.40 per day giving a net profit per cow of $4.20.

The milking and shed costs need to be taken into consideration, however, if a relief milker is needed whilst having a well earned rest, it is easy to show a substantial economic benefit from keeping cows milking rather than drying them off.

Cows need an optimum 7 weeks for the udder to be spelled long enough to then be able to commence another lactation unhindered from the previous one. Once the spell is less than 6 weeks, her production in the new lactation will start to be affected. A dry period of longer than 7 weeks may help her to put on condition but will be of no extra benefit to the udder. About 10% of cows will calve up to a week early and a small number will calve more than a week before they are due. In the past farmers have chosen to give cows 8 weeks or more which allows these cows to have at least 7 weeks spell. This practice gives most cows a 9-10 week break because they are usually dried off in batches every 2-3 weeks, the earliest calvers having at least 8 weeks. If cows are dried off once weekly, this will shorten the dry period for many cows in the herd.

Cows that are 49-56 days from their expected calving date will average 52 days and very few will calve more than 10 days early giving them less than 6 weeks. The trend today is to have cows in the condition score required for calving at drying off. It is difficult to put condition score on cows in the dry period unless they have a long spell or seasonal conditions are favourable.

It is only possible to carry out this dry cow program if anticipated calving dates are reasonably accurate. Herds where diligent heat detection has occurred for most of the joining period or where early pregnancy testing (before Christmas) has occurred, the predicted calving dates should be reliable. The later the cows are due, the more likely that heat recording will be inaccurate. Usually heats are missed so cows will calve later than expected. Too diligent heat detection will result in some cows being recorded to false heats who subsequently calve to an earlier service. The whole herd would need to be dried off at least 6 weeks before calving to avoid such an occurrence.

Drying Off

As cows near the end of lactation their milk quality changes. Milk from low-producing cows may cause processing problems for some dairy products. Cows producing less than five litres per day may have an elevated cell count even if uninfected. They may contribute to a higher Bulk Milk Cell Count, even though their milk volume is low. Udder infections during the dry period can be minimised by events at drying-off.

The aim is to shut down milk secretion and seal the teat canal as rapidly as possible - this sealing usually takes about two weeks. Studies in New Zealand have shown that virtually all new infections occur in quarters where the teat canal has not sealed. Intermittent milking provides an on-going stimulus to produce milk and impedes teat sealing. If 'skip-a-day' milking is practised, mastitis risk is greatly increased.

During the first two weeks after drying-off, it is also important to minimise the number of bacteria that contaminate the teats. Teat dipping after the last milking ensures complete coverage of the teat by disinfectant and reduces the number of cow-associated mastitis bacteria present on the skin. To reduce the number of environmental mastitis bacteria, areas where cows lie should be as clean as possible, with no bare ground or heavy manure soiling. Outbreaks of Pseudomonas mastitis have been recorded in situations where cows lie in wet conditions in the first few days immediately after drying-off. These infections may be very severe (often fatal) and are virtually impossible to treat.

Reducing yields

One week prior to the final milking date:

Stop feeding all concentrates.

Three days prior to the final milking date:

Move to a paddock with very little feed.
Reduce feed intake to maintenance level eg. approx. 7-8 kg hay for a cow weighing 500 kg.
Separate the cows from the main herd if practical.
Change routine for milking if practical eg. bring the cows to the milking area through a different entry.

Note that for higher producing cows, and in some seasons other methods will need to be adopted to reduce the milk production to less than 12 litres per day. Animal welfare codes require that water is available throughout.

How should you dry cows off?

Dry-off cows if their production reaches 5 litres or less per day.
Cows producing 10-12 litres per day can be dried off abruptly.

Take steps for cows producing more than 12 litres/day, to reduce production to 12 litres or less by the drying-off date.
These steps involve reducing food intake and changing routine.

Decide the date of the final milking for target cows.
Start preparation for drying-off at least a week before date of final milking. Ideally cows should be dried off abruptly, do not skip days and preferably do not skip milkings. Once a day milking may be necessary in for cows.
Milk out as usual at each milking until drying-off. Do not deliberately leave some milk in the udder (under milk). It is not necessary to leave milk in the udder at the last milking to improve the action of Dry Cow Treatment.
At the last milking: Milk out as usual.
If Dry Cow Treatment is to be used, administer it as recommended by Countdown Downunder.
Cover whole surface of teat in freshly prepared teat disinfectant (dip is preferable to spray). Don't leave cows in laneways, yards, feed pads or calving pads immediately after drying-off.
Avoid allowing them to lie down on bare ground or areas that are soiled with manure in the two hours immediately after you give Dry Cow Treatment.
Put the cows in a dry, clean paddock (not heavily soiled with manure, no bare ground and no exposure to dairy effluent) for 3-4 days after drying-off.
This paddock should be well away from the milking herd and the milking area, so cows don't have the stimulus to let down milk.
Continue the 'maintenance only' diet for another 3-4 days for cows that were producing 12 or more litres/day in the week before drying-off.
Check the cows daily for a week. Look for swollen udders and sick cows. Treat all cows that develop mastitis.
Avoid transporting cows during this period.

This article has been modified from the Countdown Downunder Farm Guidelines.

Choosing Which Dry Cow Product Should Be Used

There are a number of dry cow antibiotics that are available and the choice of which one should be used can be difficult. The products differ in their active ingredients, the dose of antibiotic, the size of antibiotic particles, duration of action, and price.

So which products should be used?

Mastitis history of the farm
Which bacteria have been causing infections this season and in the past
Amount of clinical mastitis experienced during the calving period
BMCC
The length of dry period given to cows
Price.

While many people select the dry cow products based on price, the price difference between the cheapest and the most expensive products is less significant than the cost of additional mastitis cases, or of having a poorer cure rate.

The following example is for a herd of 200 cows. The estimated cost of a case of clinical mastitis is $150 (range $120-$180). If the difference in price between two products was $4 per cow, and the more expensive product had a better cure rate (10%), provided greater protection to cows from developing mastitis at calving, this product would only have to prevent 6 cases of mastitis for the season to pay for itself.

Products:

Cepravin Dry Cow:

cepravin is best used if the bacteria Streptococcus uberis is responsible for a majority of clinical cases or if you get a lot of mastitis at calving (greater than 3 cases per 50 cows calved). Cows treated with Cepravin DC must have a dry period of 8 weeks or greater.

Orbenin Enduro / Elaclox Extra:

600 mg Cloxacillin products with small antibiotic particle size have the highest reported cure rates for Staphylococcus aureus.

Orbenin Enduro is best used where there are numerous cows with chronic Staph infections, where the BMCC is frequently greater than 250000 or there are a large number of cows with high cell counts.

Cows treated with Enduro or Elaclox Extra must have a minimum dry period of 35 days.

Orbenin / Elaclox / Noroclox:

contain a lower dose of cloxacillin than Enduro or Elaclox Extra (500mg versus 600mg) and bacteriological cure rates have been reported to be lower than Orbenin Enduro. Cows Treated with the 500mg cloxacillin products require a minimum dry period of 30 days.

Administering Dry Cow Treatments

Administration of Dry Cow Treatment has some hazards for cows and operators. It is critical that it is carried out properly.
It is easy to introduce bacteria into the teat if the teat end is not disinfected properly, or it is contaminated before it has sealed. Infection with environmental bacteria can cause severe mastitis.
Operators can be injured by cows during administration of Dry Cow Treatment; it is important to take time and have help.
Antibiotic residues in milk and meat (including calves) must be avoided by observing the minimum dry periods and withholding periods after calving which are specified for each product. This is particularly important where cows are culled during the dry period, or calve earlier than expected.

Plan for the time and effort that treating cows with Dry Cow Treatment takes.

Administration of Dry Cow Treatment is a critical and difficult job.
Ensure that responsible operators are trained adequately in the procedure and supervised well.

To do a good job with Dry Cow Treatment, one person can only handle about 20 cows per hour.
More than one person is often needed to do the job well and reduce the hazards associated with the procedure, especially if cows are not used to having their teats handled.
Select reasonable sized groups of cows to be treated after any one milking.
If practicable, at the previous milking, draft out the next batch of cows to be treated.
Administer the treatments as recommended ensuring the teat ends are sanitised properly.
- Teat wipes are no longer provided when dry cow therapy products are purchased.
- Teat ends should be disinfected with paper towel or cotton wool soaked in 70% methylated spirits. (To make 7 parts of methylated spirits with 3 parts cool boiled water). Disinfect by vigorously rubbing the teat end for a minimum of 10 seconds. Check the colour of the paper towel, if it is dirty, repeat the scrubbing using a new piece of paper towel.
Treat all quarters of cows to receive Dry Cow Treatment (except quarters that have been dried off for some time in cows milked as 'three teaters').
If a quarter is dry, absorption of the Dry Cow Treatment in the quarter will be changed.
Dip teats with freshly made up teat disinfectant after treatment.
Even if you usually spray, dipping is preferable after Dry Cow Treatment to ensure complete coverage of the teat.
Mark the udder (e.g. with a spray paint) so that cows that have received Dry Cow Treatment can be easily recognised.
This allows easy recognition if cows rejoin the herd in error.
Record cow ID, date and product details of all Dry Cow Treatments.
If cows calve early, or a decision to cull them during the dry period is made, the date of treatment and the withholding period of the particular product must be known.
For each batch of cows treated, mark the earliest calving date allowable for the meat withholding period and minimum dry period to pass. Calves born before this date may contain antibiotics, whether they have sucked or not. They should not be sold for slaughter until the meat withholding period for that product has elapsed. Check the label.
To minimise milk and antibiotic leakage, do not walk cows long distances for 3-4 days after Dry Cow Treatment is administered.

Mastitis after cows have been dried off.

Cows are susceptible to new infections particularly in the first week of the dry period before their teats have sealed. These infections must be identified and treated so that they do not persist and create problems after calving. Remember, however, the objective is to achieve teat plug formation quickly.

Avoid bringing cows near the dairy area (or they may start running milk).
Observe every day for a week.
Do not handle - just look.
If a quarter is swollen, bring the suspect cow into the dairy area and check the udder manually.

Check for heat and pain - compare between all quarters.
Strip secretion from suspect quarter and check. It may be different from milk prior to drying off (e.g. thicker and more 'stringy') and therefore difficult to assess.
If suspicious, treat as a clinical case.
Do not remove milk or secretion from adjacent normal quarters. Treat clinical quarters by stripping out completely and using a full course of lactation antibiotic.
Veterinary advice is recommended.
Use Lactating Cow intramammary antibiotic (even if Dry Cow Treatment was previously used in the quarter).
Use the full course of the antibiotic (as recommended on the label).
Strip out completely and continue to strip out at least twice every day during the course of the treatment.
Injectable antibiotic may be appropriate.
Record clinical details.
Treat again with Dry Cow Treatment and amend record of date for Minimum Dry Period when the case is resolved.
For clinical cases that occur in the first week after drying off, re-treatment with Dry Cow Treatment is advised.

This article has been modified from the Countdown Downunder Farm Guidelines.

Nitrogen As A "Good Value" Feed Source In Autumn

Much work has been done in Western Victoria on responses to nitrogen over recent years. These responses will vary according to pasture composition, soil fertility and seasonal conditions, however it is possible to estimate within reason, the likely result of an application using the information available.

Is Extra Feed Needed?

This is the first question which needs to be answered.

What is the estimated feed requirement over the next 3 months and can nitrogen boosted pasture be included? Some herds will milk through autumn whereas the majority in the district are dry for most of April and May. Feed options for dry cows are:

Non nitrogen boosted pasture at home
Outpaddock pasture
Agistment
Hay or silage

Many farmers will plan to have a combination of most of these. If there is a shortfall, then nitrogen applied now may produce the best quality feed at the cheapest cost.

Example:

A typical well maintained pasture on reasonably fertile soils will have at least a 10:1 response to nitrogen.

Application Rate:: 40kg N/hectare
(85kg per hectare Urea or 2/3 bag per acre of urea)

A 10:1 response will grow 40 x 10 = 400kg pasture at 10kg/hectare/day over 40 days

Estimated daily growth rate

Without nitrogen 20kg/day
With nitrogen 30kg/day

To build up a feed wedge of 600kg per hectare over the 40 days from 1400kg up to 2,000kg per hectare, some of the daily growth needs to be set aside.

Growth for Pasture Wedge:: 15kg per hectare per day.
Growth left for consumption:: 15kg/hec/day with nitrogen; 5kg/hec/day without nitrogen

For farmers wishing to feed some green grass to dry cows, or milkers and build up a feed wedge, a typical autumn growth rate of 20kg/hec would hardly suffice.

A farm stocked at 2 cows per hectare would only have 5kg per hectare or 2.5kg per cow. If nitrogen is used this jumps up to 15kg per hectare or 7.5kg cow.

This is well over half of their daily requirements as dry cows.

What is the cost of Nitrogen Boosted Pasture?

At a 10:1 response, for each tonne of nitrogen applied, 10 tonnes of feed are grown.

1 tonne of nitrogen = 2.2 tonnes Urea.
2.2 tonnes of urea spread= 2.2 x $350= $770
1 tonne of feed = $77 (.64 c/MJ)

What are the advantages of Nitrogen Boosted Pasture?

It allows the farmer to more easily build up a feed wedge approaching winter
It provides the cheapest source of purchased feeds if seasonal conditions are adequate
It is a high energy and protein feed
There is no work involved to feed it out
The benefits of good seasonal conditions and a favourable response to N will be reflected in increased body weight in dry cows and more milk in early calvers and a reduced cost per tonne of feed.
It can potentially have minimal wastage when grazed compared with losses incurred feeding hay.

Following reasonable rains and an early start to autumn growth this year, pastures are already in a responsive state for nitrogen. An application of 40kg of N/hectare (85kg urea) in damp conditions is recommended.