Transition disease affects nearly half of dairy cows and its effects can linger long after clinical recovery. Yet when conversations turn to cow longevity, the focus often shifts to how long cows remain in the herd rather than why they leave.
According to Dr. Stephen LeBlanc, veterinarian and professor in the Department of Population Medicine at the University of Guelph, that’s the wrong way to think about productive lifespan. LeBlanc recently spoke during a Dairy Cattle Reproduction Council webinar. Rather than maximizing longevity, we should optimize each cow’s productive lifespan by preventing the diseases and reproductive setbacks that force cows to leave the herd before they reach their potential.
“We want to optimize how long they stay in the herd. Optimize, not maximize. That’s a cow-by-cow decision. Some should leave sooner, some should be around for a very long time because they have earned that and they keep earning it,” LeBlanc says.
Longevity Isn’t the Goal
Longevity has become intertwined with conversations around sustainability, profitability and animal welfare. The logic seems straightforward: healthier cows stay productive longer, require fewer replacement heifers and reduce the environmental cost of raising replacements.
LeBlanc argues the relationship is far more complicated.
While healthier cows often do remain in the herd longer, longevity itself is influenced by genetics, replacement availability, market conditions and management decisions. As a result, average herd age alone offers little insight into whether a herd is healthier or managed more effectively.
Every cow will eventually leave the herd. The real question is whether she reached the point where replacement made biological and economic sense.
“Culling fundamentally is an economic decision. The right time to sell a cow is when her future expected profitability is less than an available replacement,” LeBlanc says.
The goal isn’t to eliminate culling. Instead, it’s to prevent involuntary culling caused by disease, poor fertility or other health challenges that remove cows before they reach their economically optimal productive lifespan.
The Greatest Opportunity Comes During Transition
Although culling decisions occur at the end of a cow’s productive life, many of the events that determine whether she reaches that point begin during the transition period.
Only 56% of cows make it through the transition period without at least one health disorder. Metritis, mastitis, ketosis, lameness and other common transition diseases continue to affect a substantial proportion of cows, even in well-managed herds. Healthy cows, meanwhile, achieve pregnancy rates exceeding 50% at first insemination.
“Not getting pregnant is still fatal. Not making enough milk is career ending. Mastitis and lameness ... move from being a cow issue to being a herd issue,” LeBlanc says.
Those diseases don’t simply reduce milk production during early lactation. LeBlanc notes that pregnancy at first insemination was often reduced by 10% to 15% in cows experiencing common transition diseases such as metritis, mastitis, ketosis, milk fever, displaced abomasum or lameness, even after they recovered clinically and remained in the herd long enough to be bred. The biological effects of transition disease can therefore persist for months, reducing reproductive efficiency long after visible signs of illness have resolved.
The Britt hypothesis, which proposes that follicles destined to ovulate after calving begin developing months earlier during the period of greatest negative energy balance, may also come into play. LeBlanc suggests excessive inflammation should be considered alongside energy balance, pointing to evidence that inflammation around calving can impair both oocyte quality and the uterine environment for at least three months after calving. The implication is clear: protecting cows through the transition period supports not only immediate recovery, but also fertility months later.
Older Herds Don’t Always Tell the Full Story
LeBlanc also challenges another common assumption: that increasing herd age automatically reflects improvements in herd health.
Instead, today’s older dairy herds may be the product of changing market conditions rather than healthier cows.
High beef-on-dairy calf values have encouraged many producers to breed more cows to beef sires, reducing the supply of dairy replacement heifers. With fewer replacements available, producers have retained older cows longer than they otherwise would have.
“People are retaining milking cows longer. Not because their welfare has gotten better, but because there are fewer replacement animals available,” LeBlanc says.
When evaluating herd performance, average cow age should therefore be interpreted cautiously. An older herd may reflect excellent transition management and fertility, limited replacement availability or a combination of both.
Optimizing Productive Lifespan
LeBlanc emphasizes that optimizing longevity does not mean every cow should remain in the herd as long as possible.
“Some animals should have a short productive life in the herd if they are really just not making it in terms of their performance,” he says.
The objective is to help healthy, productive cows remain in the herd until replacement is economically justified, while avoiding premature losses driven by disease.
That philosophy also extends to reproductive management. Economic models continue to support calving intervals of roughly 12 to 13 months, with cows ideally becoming pregnant by around 120 days in milk. Beyond that point, delayed conception can represent an opportunity cost of approximately $1 to $5 per cow per day, depending on herd conditions, through lost future milk production and calf revenue.
The message is less about extending longevity than influencing the biological drivers that determine it. By reducing transition disease, improving fertility and preventing involuntary culling, each cow’s productive lifespan can be optimized rather than simply keeping cows in the herd longer.
