The percentage of your herd that gets in-calf during the first six weeks of mating is your 6-week in-calf rate (often referred to as 6WICR), a key driver of farm profitability.
Every 1% improvement in your 6-week in-calf rate results in an increase in operating profit of at least a $4/cow, based on the DairyNZ Gap Calculator1. Your 6-week in-calf rate influences your not-in-calf rate. The more cows in-calf early, the fewer cows will be empty at the end of mating. Every 1% decrease in empty rate means an additional profit of at least $10/cow.
In 2023-24 across the industry, we saw the average 6-week in-calf rate increase by 2.7% and the not-in-calf rate reduce to 15%. This was worth $130.7 million in extra milk revenue to New Zealand farmers.
How does a better 6WICR increase farm profit? With more cows in-calf earlier, you get:
1. More days in milk
2. More milk in the vat early in the season (matching quality pasture to demand)
3. High breeding worth, early replacements
4. Increased ability to cull cows for non-repro reasons.
Waikato farmers target the premating period
Simone and Dale Brown are calving 310 cows in Otorohanga and focus on premating to improve their 6-week in-calf rate.
“Pre-mating is where it’s at. When you are winning at pre-mate, you have options. You know exactly where you stand 10 days out (from mating), and then you can make decisions about what to do next, like using CIDRs,” says Simone.
If more than 75% of the herd are cycling 12 days before the planned start of mating, a 6-week in-calf rate of >78% should be achieved. If less than 75% are cycling, be proactive and make a plan with your vet to manage your non-cyclers. Simone also stressed the importance of ensuring cows transitioned well, only moving them to twice-a-day milking once the cows are looking well.
With minimal use of CIDRs (young, early calvers only) and heat detection done using tail paint, the couple achieved a 6-week in-calf rate of 80% last season. They focus on metrichecking any early calvers with retained membranes.
Simone and Dale are proud of having no empties in their second calvers for the last two seasons. “It’s really important to keep those young girls in the herd,” she says, which is reinforced with a focus on growing the heifers well and keeping them fully fed.