Probiotics help calf rearing systems
Success in calf rearing is often measured by minimising health issues and achieving target weaning weights.
But reproductive performance starts long before the AB technician shows up or the bull goes out. One of the most overlooked drivers of poor in-calf rates is what happens during the transition period (the three weeks before and after calving).
Transition Stress
We always look at the transition period as one of the most metabolically stressful stages of a cow’s lactation. At calving, her demand for calcium spikes, her dry matter intake lags behind her energy requirements, and her immune system is under pressure. Most farmers are familiar with the risks of milk fever and ketosis, but even when cows don’t show obvious signs of trouble, subclinical issues often take a toll on reproductive systems.
A cow dealing with negative energy balance in early lactation will start mobilising fat reserves. This releases non-esterified fatty acids (NEFAs) into the bloodstream, which puts pressure on the liver. High NEFA levels are associated with fatty liver and impaired liver function, and that matters because the liver plays a vital role in hormone metabolism and immune function.
A compromised liver delays uterine recovery and ovulation, as well as affecting milk production. That’s why cows that have a rough transition, even if they don’t show signs of metabolic disease, will often cycle late and have a lower chance of holding to first service.
Mineral status matters more than you think
Trace minerals are another piece of the puzzle. Low selenium and zinc levels impact immune function and uterine repair. Copper is essential for hormone production. If cows calve down with borderline or deficient levels, their ability to clean out, fight infection, and return to cycling is compromised, often without any clear outward signs.
In a seasonal calving system like New Zealand’s, timing is everything. Cows that don’t cycle within the first 30 to 40 days post-calving are unlikely to conceive early. That means fewer first or second-round pregnancies, making for more late-calving cows next season. These issues can just keep flowing on unless drastic measures are undertaken to tighten the calving spread.
It's not just the sick cows
One of the most frustrating things for farmers is when healthy-looking cows fail to get in-calf. No lameness, no milk fever, no mastitis, but they don’t cycle in time, or they keep coming back empty.
The issue is often subclinical. These cows might be running on marginal mineral levels. They may have struggled with mild ketosis or liver stress that didn’t show clinically. If we could look under the bonnet, we would see that their systems aren’t quite firing, and by the time it comes to mating, the window to fix the problem has passed. That’s why a proactive approach to transition is important. It’s not about putting out fires after calving. It’s about setting up every cow, especially those in their first and second lactation, to glide through early lactation without compromising fertility.
Supporting cows with the right mineral plan
A successful transition programme starts with the right pre-calving minerals. A negative DCAD supplement helps cows mobilise calcium efficiently at calving, reducing the risk of subclinical milk fever and supporting metabolic balance. That sets the foundation for good intake and energy status post-calving.
After calving, cows need a mineral blend that supports liver function, maintains trace mineral balance, and aids immune recovery. This helps cows get back on track quickly, reducing the risk of delayed heats and silent ovulation.
It’s also important to keep the programme going for an adequate amount of time. Transition minerals should be in place for at least 21 days pre-calving and continued post-calving through the early stages of lactation. This supports mineral availability during the peak stress window and helps the liver recover from the load of fat mobilisation and hormone cycling.
Reproductive gains start earlier than you think
When transition is done well, cows bounce back faster, cycle sooner, and hold better to first service.
Good reproductive performance is always a result of multiple factors, but transition is one of the few that you can lock in ahead of time. You don’t need to wait for problems to show up. With the right nutrition plan and the right minerals, you can improve your odds before the season even starts.
Chris Balemi is Agvance Nutrition founder and managing director.
