Improving herd fertility is an ongoing focus at Southern Dairy Hub. A recent reproductive review offers insight into what’s working, where there’s room to grow, and how strategic decisions are shaping outcomes across seasons.
Over the past year, we have conducted a reproductive review of our herd, assessing matings, conception rates, body conditioning scores, and 6-week in-calf rates (6WICR).
In September 2024, the Southern Dairy Hub Future Farm Systems Demonstration trial separated the herd into two:
The Future herd – Higher genetic merit cows (127 BW difference) with a lower stocking rate (2.5), less imported lactation supplement, wintered on baleage.
The Standard herd – average BW Southland herd stocked at 3.2 cows per ha wintered on swedes.
This allowed us to complete the DairyNZ winter 2024 farm systems trial before distributing the cows. It has, however, made interpreting the results a little more challenging as the cows were sitting in different herds through calving.
Mating Performance
The herds averaged a 6WICR of 73% (Future herd: 71%, Standard herd: 75%). These results are slightly lower than last season’s results (74%) but still above the industry average of 69.3%.
Our two-year-old calving pattern among the Standard herd is excellent (97% 6WICR), with both Standard and Future two-year-old herds averaging 95% and 93%.
As expected, the 6WICR across the combined herd steadily declines as the cows age (two-year-olds: 81%, three-year-olds 75%, 4-8-year-olds 71% and 9+ year-olds 69%). Given that our three-year-olds comprise 20% of the herd, these results were significant.
This is reflected in the conception rates, with two-year-olds recording a 67% conception rate in the first three weeks compared to 59% for three-year-olds and an average of 54% for cows aged 4+. Interestingly, the two-year-olds recorded a 0% conception rate after 9+ weeks, which LIC tells us is highly unusual.
The overall conception rate was 52% (MINDA). When we delve into the data at a combined herd level, the conception rates across the board in the first three weeks were poor (average: 46%) compared to the second three weeks (63%), resulting in lost days in milk. This has been traced back to a problem with dry matter intake leading up to mating, particularly in October. The sodden conditions we were farming in last spring certainly had an impact. Very limited pasture availability and high feed wastage negatively impacted dry matter intake and the energy balance of the cows. The damage to paddocks has impacted farm grass growth all season. We have been reminded of the critical importance of cow nutrition to dairy farm productivity, as it underpins cow production and reproductive performance and therefore farm profitability.
Body condition scores
Body condition scores recorded reflect the repro performance among the various age groups. The two-year-olds averaged 4.6BCS going into mating, which likely reflects their excellent 6WICR.
The mixed-aged cows had the lowest performance, and we can see from our BCS data that they were a little heavy at calving (5.5BCS) and then dropped 1.5BCS by mating (higher than the target of less than 1BCS). Mobilising too much body fat and protein has likely had an impact on our early days of mating. It took a good three weeks into mating for us to get them on a rising plane of nutrition.
Interestingly, both the Standard and Future herds gained BCS while still milking – not many cows manage to achieve this, according to LIC’s MINDA data. This bodes well to maximise days in milk in the later part of lactation, provided the cows are not too heaving going into calving.
Standard Herd BCS
Future Herd BCS
What went well?
When we think back on the things that worked well leading into mating one of them was the separation of the two- and three-year-olds into their own mob in early September. This age group has certainly performed a lot better across the board. When cows are moved into different mobs, there is a change to the social hierarchy. We know that young cows are more likely to be bossed around by the older girls, so having the young cows in their own mob likely reduced the level of social stress that they had to contend with as they recovered from calving.
What could we have done differently?
Looking back, we could have better-managed pasture utilisation and balancing nutritional requirements for our mixed-aged cows through the wet period. While our focus at the time was trying to minimise BCS loss the utilisation of feed was a challenge.
We are in the process of developing a plan for the upcoming season including:
Having a full farm team pre-calving and pre-mating session including our rural professional support networks to ensure a thorough and robust plan.
Managing BCS so cows can stay on maintenance diet over winter (or gain just a little) ensuring the mixed-aged cows especially are at target weight at calving (not too over conditioned)
A real focus on the transition to lactation with this plan being in place from 1 June 2025
Consideration of higher use of synchrony to regain some of the lost days in milk
