As we head into the latter half of the year, New Zealand dairy farmers are already setting their sights on mating season. It is no secret that cows in peak physiological condition achieve the highest in-calf rates, but navigating the nutritional demands of early lactation to get them there can be challenging.
Often, the primary hurdle is ensuring that cows receive the precise mix of trace minerals, energy and protein required to balance their pasture-based diet. Suboptimal nutrition does not just affect milk yield; it also directly influences reproductive success.
The health and efficiency of the rumen influence how well a cow performs during the metabolic stress associated with mating and reproduction. A cow with suboptimal rumen function remains in a state of negative energy balance (NEB) for longer, placing her at a much higher risk of ending the season empty.
Successful herd reproduction relies heavily on a thriving rumen microbiome. Along with nutrients absorbed directly across the rumen wall, the large population of microbes produced through rumen fermentation provides a major source of nutrients. As these microbes pass through the gastrointestinal tract, they are digested and supply the cow with high-quality microbial protein. This is an essential component in repairing the reproductive tract after calving and supporting ovulation.
Alongside balanced nutrition, maintaining a stable rumen pH throughout lactation is vital. In the lead-up to mating, lush, leafy spring pastures in New Zealand are often low in effective fibre and high in soluble sugars, which can trigger subacute ruminal acidosis (SARA).
To support strong submission and conception rates, diets should be formulated to buffer and stabilise rumen pH. This may require incorporating higher levels of quality supplementary fibre, targeted rumen buffers or a combination of both.
Regularly checking your herd’s body condition score (BCS) helps ensure that cows have the energy reserves required to cycle naturally. According to industry research by DairyNZ, a cow should not lose more than 1.0 BCS between calving and mating. Excessive condition loss during this period can substantially reduce the likelihood of successful conception.
If your herd is losing condition too rapidly, you must intervene quickly. You can:
The mating period is not just about getting cows in calf; it encompasses the crucial months leading up to submission and the entirety of the first trimester. Any sudden decline in nutrition, trace-element deficiency or imbalance in rumen pH during early gestation can compromise the embryo and contribute to early embryonic loss.
Improving the reproductive performance of your cows can make a significant difference to your farm’s profitability. Although every farm is different and exact mineral requirements vary by region, the fundamental rule remains the same: precise nutrition is non-negotiable.
If you want to take the guesswork out of your herd’s mating nutrition, our team can help formulate a customised mineral blend specific to your soil and pasture profile. Getting this right is one of the most logical and effective ways to support reproductive success this season.
For optimal reproductive performance, mixed-age cows should have a BCS of 4.0 or higher at mating, while first- and second-calving cows should have a BCS of 4.5. Crucially, cows should not lose more than 1.0 BCS between calving and mating.
A low or unstable rumen pH, often caused by lush spring pasture, reduces feed-digestion efficiency and can push the cow into a more severe negative energy balance. This energy deficit can delay the return of regular oestrous cycles and substantially reduce conception rates.
To minimise condition loss, ensure that cows have adequate dry matter intake. Supplement with high-energy feeds if pasture availability is limited, use rumen buffers to support digestion, and consider placing lighter cows on OAD milking to reduce their energy output.
