Thursday, April 25, 2024

Monitoring reproductive performance: breeding off a baseline

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It is so hugely linked to the profitability of your farming operation that simply looking at a value like empty rate does not scratch the surface.
Before setting out to optimise reproductive performance, you need to know how your herd is performing now.
Reading Time: 5 minutes

By Rory Dean

This article first appeared in our sister publication, Dairy Farmer.

Like many aspects of farming, in order to improve you must first ensure you understand how you are currently performing. This is increasingly important as costs rise for farming operations throughout New Zealand. 

Many of the key factors of reproductive performance are included in the Fertility Focus Report. Standing out at the top of the FFR is the six-week in-calf rate (6WICR), the number of cows that have conceived in the first six weeks of breeding. A higher 6WICR suggests better reproductive management, and is directly related to increased profitability on NZ farms. 

A higher 6WICR is valuable to farmers for several reasons. These include: cows spend more time “in milk” and so have more productive lactations, faster genetic gain due to more AB replacements, increased opportunities to cull late-calving cows or culling cows on type, and a tighter calving pattern. 

While the industry target of 78% can seem unrealistic to many farmers (the NZ average is about 66%), trying to improve performance will pay. 

“Gap” calculators are available on both the DairyNZ and LIC website to allow you to gauge the increase in operating profit you could derive from improving 6WICR and not-in-calf rate.

Benchmarking data for 6WICR, Kaipara district, Northland, shows a difficult year for many farmers due, in part, to reduced feed quality in spring. It is only through measuring one can understand how their performance compares.

Not-in-calf rate is a measure of the number of cows that have a negative pregnancy diagnosis, and cows that calved this season but don’t have a pregnancy diagnosis or are still recorded doubtful, over the total group of cows. It is subtly different to empty rate, as empty rate is the number of empty cows divided by the total herd on the day of pregnancy testing. If cows have left the herd since calving and do not receive a pregnancy diagnosis, they are included in the not-in-calf rate calculation but are not involved in the empty rate calculation.

One of the main questions I receive from farmers is “What are empty rates like this year?” There are two issues with this seemingly simple question. One is that empty rates are a (typically) poor measure of reproductive performance in a dairy herd. The reason behind this is simple – one is not comparing apples with apples. 

As we can see in Fig 1.2, actual benchmarking data from the Mid-North region shows a huge variety of mating lengths on dairy farms. Obviously the very short breeding periods are representative of split calving herds but it is not uncommon for mating lengths to vary from nine to 16 weeks. We know, through DairyNZ studies, as well as a basic knowledge of cattle, that the longer we mate cattle for, the more of them will become pregnant.

Mating length benchmarking data for farms in the Kaipara region, Northland. Below nine-week breeding periods are associated with split calving herds.

We must be very careful interpreting reproductive performance because there are many factors that may affect it, and it is only through careful, deliberate discussion with your local vet or farm consultant that you can truly give it justice. It is so hugely linked to the profitability of your farming operation that simply looking at a value like empty rate does not scratch the surface.

Submission rate and conception rate are the main drivers of 6WICR. A submission rate of over 90% and a conception rate of over 60% is required to achieve the target 6WICR of 78%. In brief, eight factors are largely responsible for reproductive performance in our herds. These are: 

• Calving pattern – have late-calving cows contributed to an issue? 

• Heifer management – well-grown, early-calving heifers perform better when they enter the herd.

• Nutrition and body condition – aim to calve cows down at BCS 5 (R2s/R3s 5.5) and minimise BCS loss in early lactation.

• Heat detection – missed heats are very costly and a missed opportunity. Paddock checks can help hugely.

• Non-cycler issues – non-cycler cows need to be identified and intervened with early to achieve a good return, regardless of strategy.

• Service bulls – roughly one bull to 30 non-pregnant cows is sufficient. Bull health is often overlooked and can lead to high not-in-calf rates.

• AB and genetics – trained, experienced AI technicians get better results than DIY AI technicians.

• Cow health – a high prevalence of mastitis, lameness, or endometritis (dirty cows) can lead to poor performance. Trace element deficiency can play a role.

This is an oversimplified look at some of the issues affecting how well mating is going on farms, and a true reproduction review is required to tailor an individual plan for your business going forward. 

There are numerous strategies to achieve improved performance in your herd. Preventing non-cycling cows is the key.

Two key factors I have noticed are: 

• Flexible milking/OAD milking – I’ve been really impressed with the improved condition of cows going into mating, seeing cows and heifers transition far better into lactation. This, alongside the obvious savings and improvement in farmer wellbeing, has not been matched with a huge decline in production, as is often the concern. Listening to local farmers, the best way to consider a move to OAD milking is to talk to farmers around you or attend a local discussion group. 

• Collar technology – Cow collars are revolutionising the NZ dairy industry. Rumination data can help us improve the transition and health of cows to minimise non-cycling cows, and heat data allows for breeding timeliness to be optimised, even in those cows that have short, quiet heats. We are all on a learning journey with what this great technology can offer the NZ dairy industry, but I have not heard one of our farmers complain about collars once they have decided to go down this route. There are considerable differences in pricing and functionality of different collars available – do your research. 

In summary, if you are motivated to optimise reproductive performance on your farming operation, you first need to know how your herd is currently performing. Consider involving your trusted farm adviser to conduct a comprehensive herd reproduction review with you, tailored to your business and goals. Use benchmarking data if available – but remember, empty rates have their limitations; focusing on 6WICR allows more accurate comparison. 

If you are considering changing your business model to allow for OAD milking or utilising collar technology, get involved with your local discussion group, and take notes.

Who am I? Rory Dean is a farm animal veterinarian practising in the Kaipara District of Northland

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