Short dry periods – does the money stack up?

This final supplement dedicated to investigating the effect and impact of short dry periods aims to answer one of the most important questions – what about the money?  Vet Chris Watson of Wood Vet Group in Gloucester takes a look at some of the figures.

Although the UK will probably not adopt the very short dry periods we see in the USA, dry periods of around 35-45 days are becoming increasingly common.  However, should talk from sceptics about reduced yields in subsequent lactations deter people from exploring it as a management tool for their unit?  The answer, according to Mr Watson, is no.

First, we should accept that the adaptation of a 60-day dry period was somewhat arbitrary and seems to be founded on what suited previous systems.  Research shows that it was established, during the war years of the 1940s, that the ‘ideal’ length for the dry period was 60 days.  This produced the best efficiency for milk production, enabled producers to control the calving index and accelerated the prospects of genetic improvement.  This gave rise to the accepted lactation length being defined as 305 days – 60 days off a 365 day calving pattern.

In more recent studies designed to examine different dry periods in cows and assess the subsequent lactation yield, it looks as if there is a consistent picture emerging: -

·         For dry periods down to 30 days there is little or no change in the subsequent milk production.  Studies show between 0% and 3% decrease in yield.

·         For cows that have no dry period there is a subsequent reduction in milk yield of around 18-25%.  This is a consistent and large effect.

Work has also shown that milk composition improves with short dry periods which clearly has an economic benefit.

So what else?

Other benefits to be expected of short dry periods are:

·         Fertility performance

·         Mastitis control

·         Periparturient health

Studies have shown that cows tend to lose less body condition score on a short dry period regime, which has a knock-on effect of reducing the days to first ovulation, and days open (empty).  (see table below).

The table above shows a trial involving 772 cows assigned to 2 dry period lengths   (Grummer)

What is mastitis? The udder is 10 times as likely to become infected with new mastitis-causing organisms during the dry period, as during lactation, so there is the potential for a lot of new infection coming in as well as established infections being cured.  In fact the level of new infection during the dry period is much more likely to determine the overall balance of infection over the dry period than is the cure rate from previous infections in the preceding lactation.  Shortening the dry period, and using an appropriate tube such as Cephaguard® DC should reduce the window for infection and, hence, mastitis cases.  This approach is relatively new in the UK, but farm examples to date are extremely encouraging.

The money part

The table below sets out the cost factors involved for milk production by shortening the dry period. The table assumes: -

·         No change in milk quality (it is however likely to improve with a short dry period)

·         All year round calving

·         Standard 8000 litre cow

·         No seasonal effect milk on production

·         The baseline comparison is against 60 days dry = 0 litres difference

·         Reducing the dry period down to 30 days will cause no loss of milk in the next lactation

·         Yield decline is a standard 2.5% per week after peak yield

·         400 Day calving index

·         Feeding a dry cow costs £1.00 per day

·         Feeding for milk yield is between 0.3 and 0.46 kg concentrates per litre depending on yield

⁽¹⁾ The costs incurred in feeding the cow for extra milk yield less the value of the milk produced = margin over the concentrate feed.

⁽²⁾ Total savings per cow = margin over concentrate feed + dry cow feed savings

@ 40 days dry

·         33% less dry cows

·         4% extra milk

·         £45 per cow extra margin over purchased feed concentrates

·         £65 total saving per cow