Improving Dairy Herd Reproductive Performance in Canterbury 

Reproductive performance is the engine of a profitable dairy farm. Every cow that fails to get in calf on time represents lost production, added costs, and a harder end-of-season cull decision. And yet, in many Canterbury herds, there is significant room to improve – not through expensive interventions, but through a systematic, planned approach. 

At Aorangi Vets, reproductive services are one of the most valuable things we offer dairy clients. This guide covers the key drivers of herd fertility, what the numbers mean, and how we can work with you to lift performance. 

Why Reproductive Performance Matters 

The economics are straightforward. A cow that conceives in the first three weeks of mating produces more milk over her lifetime, is more profitable, and fits neatly into a seasonal system. A cow that conceives late – or not at all – costs money every day she stays in the herd beyond her productive contribution. 

Key financial impacts of poor reproductive performance include: 

• Reduced 6-week in-calf rate, leading to more late-calving cows the following season 
• Higher empty rates and increased cull cow costs 
• Lower peak milk production from late-calving cows 
• Increased feed and management costs for not-in-calf animals 
• Reduced genetic gain from lower numbers of replacement heifers 

Key Reproductive Performance Benchmarks 

Understanding where your herd sits against industry benchmarks is the starting point for any improvement programme. The key metrics to track are: 

• 6-week in-calf rate: The percentage of cows pregnant within six weeks of the planned start of mating (PSM). Target: 78% or above. 
• Not-in-calf (empty) rate: The percentage of cows that are not pregnant at the end of the mating period. Target: below 10%. 
• 3-week submission rate: The percentage of cows submitted for insemination or natural mating in the first three weeks. Target: 90% or above. 
• 3-week conception rate: The percentage of mated cows that become successfully pregnant in the first 3 weeks of mating. Target: 55–60% or above. 

If your herd is falling short of these benchmarks, it is worth understanding whether the issue lies with submission rate (are cows cycling and is your heat detection working?), conception rate (are they getting in calf when mated?), or both. The causes – and therefore the solutions – are different. 

What Drives Poor Submission Rate? 

A low submission rate in the first three weeks of mating typically means cows are not cycling, or that heat detection is missing them. Common causes include: 

Anoestrus – cows not cycling 

Post-calving anoestrus is the most common reason for poor submission rates in New Zealand dairy herds. Cows that are in negative energy balance, have low body condition at calving, or have had a difficult calving are slower to resume cycling after calving. 

The target is for cows to have resumed cycling by three to four weeks before the planned start of mating. Cows that have not cycled by the time mating starts will not be submitted in the first three weeks – directly reducing your 6-week in-calf rate. 

Management levers that improve anoestrus rates include: 

• Proper transition management (from 3 weeks before to 3 weeks after calving) is one of the most effective strategies to reduce anoestrus cow rates. 
• Meeting body condition targets at calving (BCS 5.5 for first and second calvers, 5.0 for mixed age cows). Cows will have enough reserves to offset condition loss in early lactation leading into mating. 
• High-quality nutrition in early lactation to prevent a negative energy balance. Negative energy balance occurs when a cow’s energy intake does not meet the massive demands of milk production in early lactation. 
• Prompt treatment of health issues post-calving – metritis, mastitis, and lameness all delay return to cycling 
• Considering early interventions for non-cycling cows, for example intrauterine progesterone devices (CIDR) 

Heat detection 

Even in herds where cows are cycling well, poor heat detection means missed matings and lower first-cycle submission rates. InCalf research indicates heat detection errors are limiting reproductive performance in around a quarter of seasonal-calving herds – and around 70–80% of cows won’t show a visible heat at their first ovulation after calving, so relying on visual observation alone means genuine heats can easily be missed. 

Options to improve heat detection include: 

• Tail paint or mount detectors – a simple, low-cost tool that, when applied correctly and checked consistently, remains highly effective 
• Electronic heat detection aids – collars, ear tags, and cameras – can be highly accurate and are useful in larger herds or where labour is constrained 
• Pre-synchronisation programmes – using hormones to synchronise a cohort of cows before mating begins 

What Drives Poor Conception Rate? 

If submission rate is good but conception rate is low, the issue lies with the ability to establish and maintain pregnancy. The main causes are: 

Nutrition and energy balance 

Cows in severe negative energy balance at mating have reduced conception rates. The uterine environment, oocyte quality, and embryo survival are all impaired when energy status is poor. Ensuring cows have access to high-quality pasture and supplements through transition and in the weeks leading up to and during mating is a key lever. 

Uterine health 

Endometritis is the infection of the lining of the uterus after calving. Most herds in NZ have around 10–25% affected. On average, cows with endometritis get in calf about two weeks later and are more likely to end up empty. Metrichecking and treating dirty cows between 10 and 21 days post-calving provides the best return on investment and increase in reproductive performance. 

Cows that have had retained placentas, metritis, difficult calvings, and low BCS are at highest risk and should be flagged for reproductive examination before mating. 

Trace element deficiencies 

Selenium, copper, and iodine deficiencies all impact fertility. In Canterbury and South Canterbury, selenium and copper deficiencies are particularly common and can affect conception rate, early embryo survival, and overall reproductive efficiency. Pre-mating trace element testing is a worthwhile investment. 

Multimin injection is widely used in Canterbury dairy herds as a pre-mating trace element supplement, with good evidence for improving conception rates in deficient cows. 

BVD (Bovine Viral Diarrhoea) 

BVD is an important cause of early embryonic death and reproductive failure in cattle. Herds with undetected Persistently Infected (PI) animals circulating BVD virus will have reduced conception rates, increased early returns to service, and unexplained reproductive failure. BVD management is covered in more detail in our BVD guide – see the internal link below. 

Pre-Mating Planning with Aorangi Vets 

The best reproductive outcomes come from planning that starts well before mating – not from reacting to poor results at scanning. At Aorangi Vets, we work with dairy clients through a pre-mating programme that typically includes: 

• Reproductive examination of problem cows and non-cyclers in the weeks before mating 
• Assessment of body condition and nutrition planning 
• Trace element testing and supplementation planning 
• Review of BVD status and vaccination programme 
• Tail paint application and heat detection planning 
• Pre-synchronisation or OvSynch programmes where appropriate
• Discussion of artificial insemination (AI) programme planning and bull management 

If you want to set up a pre-mating visit for your herd this season, get in touch with your nearest Aorangi Vets clinic – the earlier we plan, the more options we have. 

Reading Your Scanning Results 

Scanning is the moment of truth. When you get your results back, the data tells a story – and it’s worth reading carefully: 

• A low 6-week in-calf rate with a good submission rate points to a conception rate problem – look at nutrition, uterine health, and trace elements 
• A low submission rate with a reasonable conception rate points to anoestrus or heat detection – look at body condition, post-calving health, and detection methods 
• A high early embryo loss rate (cows that conceived but lost the pregnancy) can indicate BVD, nutrition issues, or heat stress 
• A tail of late-calving cows that repeats each season suggests a systemic issue worth investigating with your vet 

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