A large number of dairy cows leave the herd in early lactation largely due to metabolic health reasons, and the risk of death is highest early in lactation. The most common “reason” for a cow to leave the herd in the US is death, comprising 21 % of the turnover of cows. Involuntary culling of cows early in lactation is expensive, in the order of $500 to $1000 (380 to 760 EURO) per cow (US data). This does not include losses in milk yield due to disease or extra labor and delayed replacement. Efforts to reduce death rates and improve early lactation health are therefore often profitable. Cull risks vary within herds, depending on such things as health, milk production and reproduction. External factors are the availability of replacement heifers, parlor capacity or land availability.
The productive lifetime of the cow
The annual cull rate for cows in the USA in 2013 was around 40 % and it has been fairly constant during the last 20 years with a slow rise. This is equivalent to a productive life time of 2.63 years, or 31.6 months. The average dairy cow longevity is therefore approximately 57.1 months or 4.8 years in the U.S. Productive life time has decreased from 35 months for cows born in 1960, to about 27 months for cows born in 2000. The annual cull rate has increased from 17% to 43% in the same period. This shorter lifespan is primarily the result of the dairy producer’s decision making process. Dairy producers cull cows because they are no longer profitable or they are replaced by more profitable cows. Culling decisions are made based on factors belonging to the cow, such as health, milk production, and reproductive status, but also on external factors such as the availability of replacement heifers, parlor capacity or land availability and prices.
Cost of involuntary culling
Death or culling early in lactation is very costly, estimated to between 500 and 1000 USD/cow, and this does not include the indirect, hidden costs involved, such as reduced milk yield, labor and veterinary costs. A replacement decision model made by de Vries showed that a reduction in involuntary culling rate for the first 3 months only, by 50% and 100% resulted in gains in profit of $37 and $77 per cow per year. These gains likely underestimate the true benefits of reducing fresh cow culling through improved management and cow comfort, because effects on milk production and fertility are not included in these gains.
Cull risks and culling reasons
For a cow the risk of being culled is larger during the first 60 days of lactation, which is a period when cows often have problems. In general, pregnancy, higher milk production, younger age, and the absence of health issues such as metabolic problems, lameness or mastitis reduced the risk of culling.
A study from 2010 on farms in the eastern USA showed that the number one reported reason of cows leaving the herd was death, 21% of all cullings (including cows that could not walk onto the truck and had to be euthanized), followed by reproduction problems 18%, injury or other reason 14% and low production and mastitis, both 12%. Death is a big concern. It is not only an economical issue but a potential consumer issue as well.
Several herd factors are associated with cow longevity: herds that are trying to expand or use cross bred cows had lower cull rates. In a study with larger dairy herds in the eastern U.S., the culling risk increased for cows in herds with shorter days to first insemination and herds that used a synchronized breeding program.
An increase in on-farm mortality (euthanasia and death) in dairy herds has been reported in several countries in the last decade. Death rate in Sweden was 6.6% in 2010. In Swedish dairy herds, higher mortality was associated with larger herd size, longer calving intervals, and herds that had Swedish Holstein as the predominant breed. Lower mortality was observed in herds with a higher herd average milk yield, during the fall and winter, and in organically managed herds. In a review of the literature, these authors reported that in general death risk (mortality rate) increased with an increased proportion of purchased cows, no pasture-grazing, larger herd sizes and lower herd average milk yield.
Keeping the cow in the herd
Cows are culled to make place for the new heifers. But with such a good availability of heifers, like the present situation in the USA, farmers are less likely to see the opportunities that lie in working with management and barn environment to try and keep cows healthy, so that they can be kept in the herd, and the hidden costs behind the culling, the tip of the ice berg of e.g. lameness and mastitis that Rushen mentioned: lower yield, vet costs etc. can be avoided.
- Cow longevity depends on intrinsic and extrinsic factors.
- Survival analysis has shown that a large number of cows leave the herd early in lactation largely due to metabolic health reasons.
- The risk of death is greatest early in lactation.
- Forced culling of cows early in lactation is expensive, in the order of $500 to $1000 per cow.
- Efforts to reduce death rates and improve early lactation health, and therefore intrinsic cow longevity, are to be profitable.
- The average cow longevity is determined by extrinsic economic factors unrelated to an individual cow’s health and performance. To extend the average cow longevity, dairy farmers would need to be motivated to bring fewer heifers into the herd and therefore cull fewer cows.
- This could be accomplished by creating fewer dairy heifer calves, for example through delayed inseminations in heifers and/or cows, or not breeding non-pregnant cows that are late in lactation.
- A portion of the heifers and cows could also be inseminated with beef semen and the crossbred calves could be sold.
- Recent analyses have shown that these are viable options under some constraints and price assumptions but cannot be generally recommended under current market conditions.