Nantglas Project Update: Are you challenging your six-week in-calf rate?

For every 4% increase in six-week in-calf rate, there is a possibility of reducing the empty rate by 1%. Not only does improving the six-week in-calf rate aid farm profitability, but also improve herd genetics and quality from having more choice of high-quality replacements and cows to keep. At one of Farming Connects dairy demonstration sites in Carmarthenshire, we are concentrating on reducing the calving blocks from 12 weeks to 9 weeks. Originally, the target was 10 weeks – this is now challenged further. Iwan Francis, who farms at Nantglas in Talog, currently runs two calving blocks of 100 cows and doing the AI himself, which amounts to 48 weeks of calving and service through the year. This takes a lot of labour time for Iwan, which takes his time away from other important aspects of the farm. Kate Burnby, the specialist vet from StockPlus+ Positive Farm Advice, recently joined a Farming Connect webinar to discuss some key steps to consider to maximise the six-week in-calf rate.

  1. Putting targets in place:

According to Kate, farmers should aim for a 78% six-week in-calf rate. This is the leading measure of dairy herd’s reproductive performance. The key targets to consider are:

  • Six-week in-calf rate: 78%
  • 21-day submission rates: 90% or above
  • Conception rate: 60% or above
  • 12-week not-in-calf rate: 10% or less

2. Heifer management

Farmers often aim for 20% replacement rate and heifers have a vital role in reaching reproductive targets. Kate advises farmers to analyse their herd age, structure and culling strategy. If you lose a high number of cows before they complete four lactations, you should consider why first, second and third lactation cows are not making it. Because first lactation cows take around 10 days longer to get back in-calf compared to older cows, heifers demand more recovery time. By ensuring heifers are frontend loaded i.e. mate them to calve at the very start of calving block or just before the main herd, it gives the heifers the best possible start and improves their chances of longevity within the herd. 

Iwan aims to have 90% of heifers calved by week 4 of calving. To do this, 15-month-old heifers need to be a minimum of 60% of their mature body weight. A synchronisation programme is used and will start mating the heifers around seven days before the main herd.


3. Body Condition Scoring (BCS)

It has been shown that a cow’s body condition score at calving is strongly connected to body condition score at mating, heavily influencing the number of days until their first cycle. We aim that 90% of cows calve in optimum body condition (2.75-3.25) and lose no more than 0.5 of a score between calving and breeding. Thin cows and cows that have experienced rapid weight loss take longer to start cycling, increasing the number of non-cycling cows in the herd and stretching the calving blocks. Scoring will take place in late lactation and if cows have a low BCS (less than 2.75) we have options e.g. aim to dry-off early and/or feed at higher level to achieve the target BCS. Fat cows are also problematic cows, prone to reproductive failure, so these are managed as well. Aim for less than 10% of cows outside of the BCS targets. If there is a significant range of BCS in the herd, it’s advised to manage the herd in different ways to ensure groups are fed accordingly. 

Graph 1 shows the 2020 spring calving performance. Note the significant proportion of late calving (week 7+) and empty cows were cows that were later calving, had calving issues/disease, or were over/under conditioned i.e. they were identified as being “at risk”.

Graph 1. 2020 spring calving performance


4. Heat detection – drive high submission rates

One of the most important factors in improving the six-week in-calf rate is heat detection, making identifying bullying cows a priority during the mating season. Failure to detect heat and errors in heat detection are the two primary causes of poor reproductive performance, affecting profitability in several ways. This could be from the longer calving intervals, lower lifetime milk production and fewer calves, wasted semen and time and culling of normal cows due to unrecognised oestrus and low conception rates.

For consistency and improvements, Kate suggested that one person is best to be responsible for heat detection, following a specific schedule and effectively communicating with colleagues. As early morning and early evening are known as the best time to observe heat, by making heat detection the first and last task of the day, you’ll take full advantage of the opportunity to observe late evening and early morning heats. For maximum conception rates, cows should be serviced within 24 hours of first observed standing heat.
If you are using heat detection technology, it is also vital that you understand your cows and the heat cycle to ensure accuracy. 


5. Healthy, fertile bulls

If you’re using bulls to cover the cows, its vital that they are in good condition and disease free. For example, if a bull runs a fever it can take two months for the sperm to recover. Along with healthy bulls, it’s also key to ensure that you have enough bulls to cover the whole herd and also reduce the risk of a non-fertile bull. This is known as bull power. The bull power you require depends on the number of open cows and the age of the bulls.

Sweeper bulls are also a key influence on the calving blocks. You may serve all cows that are in-heat promptly for 6 weeks, however, once the bull goes in with the late cyclers, a low-fertile bull will significantly affect the empty rate. At Nantglas, the first two rounds (AI) of mating went very well, achieving a 71% (target 78%) 6-week in-calf rate. However, after the sixth week when the sweeper bull went in, performance dropped, resulting in a 14% 12-week empty rate, which raised questions on the bull’s fertility. Next season this will be addressed.

Kate Burnby, a specialist in dairy fertility, put together a mating plan for Nantglas. The heifer synchrony worked extremely well with all 29 heifers holding and all bar two due to calve in the first four weeks of calving next spring. This means that Iwan is now on track to calve 100 animals in the first 42 days next spring. 


6. AI Technique

DIY AI is often a popular option on dairy farms to reduce cost and dependency on others. With an 18-hour window available to serve cows, it’s essential to ensure correct handling of semen and AI technique. If you carry out the AI yourself and are block calving, you only AI cows during the service period with the rest of year having no practise, this may impact your AI technique. There are numerous factors on how you can maximise conception rates when AI’ing such as cow positioning, thawing the straw, finding the cervix etc. It’s always an idea to complete a refresher course every couple of years to ensure your technique is up to scratch and have the best possible chance of conception. Farming Connect offer funded DIY AI training courses which you are able to apply for. Please visit the Farming Connect website or contact your local development officer for more information. 


7. Recording, analysis and planning

By keeping and analysing some simple records at calving, including body condition and health/medicine records, you can identify risk factors in your herd and put plans in place to reduce the number of infertile and non-cycling cows in the following season. These could be lame cows, cows which had previous calving difficulties, mineral deficiencies, metabolic problems or mastitis. Kate recommends a season review approach – taking time to identify what has gone well and what we can improve after each calving/mating season.

Figure 2. Example of Nantglas Calving Records for spring 2020.