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Vet's View: What are factors that are driving herd fertility up?

Analysis of the records from clients’ herds indicates that there may be growing signs of an improvement in herd fertility, as vet Chris Watson explains.

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The graph shows all the herds ranked in order of their reproductive ‘effort’ or efficiency based on the percentage of cows they get pregnant by 100 days postcalving.

 

The trend over the last three years has been that the efficiency has improved – 5% more cows are pregnant at 100 days than before. Nine herds are now at or past the key 40% threshold compared to five herds three years ago.

 

It may well be that the change in fertility profile is due to the more committed herds being left in the industry along with the bigger herds making more investment in herd management but there could also be other issues.

 

If we look at the averages across all herds we see first service interval is unchanged at 76 days and heat detection rates are unchanged and are 40-50% depending on how you measure them. Analysis shows conception rates have increased by 6% – from 30 to 36%.

 

These averages hide a lot of variation but it looks at first glance as if the conception rate is driving the improvement and although 6% does not sound a lot, it is a huge change and worth spending some time looking at what could be happening.

Sire selection

Could selection of sires with a significant fertility element be starting to show some effect? We know from work in Ireland that when fertility performance was included in bull selection the effects with improved fertility conception rates start to be seen.

 

Or is it that more herds have gone back to a technician AI service as part of an overall fertility management package? We know professional insemination techniques can produce better results.

 

Or could it be more investment in staff education and training has improved the DIY AI technique and, although heat detection rates overall have not changed, the accuracy of heat detection has improved – we are serving more cows that are truly in heat and at the right time.

 

Or maybe it is because there may be more use of simple controlled breeding systems to allow fixed time insemination or at least better targeted serving.

Conception rate by itself does not necessarily deliver pregnancies. Efficiency in fertility is getting cows pregnant in sufficient numbers in a set period of time – usually the best measure of this is the percentage pregnant by 100 days post-calving. So conception rate alone is only part of the issue and heat detection is the other key part of the equation.

 

If we look at the heat detection for first service – first service submission rate – it is measured by setting a start of breeding date, or more usually days after calving, and then by allowing cows a maximum cycle length of 24 days. The number served is expressed as a percentage of the total number of cows in this time frame. What percentage of cows got a first service during the window of 24 days after the start of breeding? The number pregnant is then the combination of this with conception rate – you spot the cow bulling and the conception rate (AI) produces pregnancies.

 

If we look at fertility performance, and check the conception rate alone against overall herd fertility ranking, there is very poor correlation. The herds with better fertility do tend to have higher conception rates but not always. The fertility improvement is not driven by conception rate alone and we have to take into account heat detection – especially heat detection for first service.

 

If we measure the efficiency of getting cows pregnant based on first service heat detection there is a definite trend agreeing with overall herd rank.

 

The herds which are better at serving cows early (on time) are the ones getting more cows pregnant on time regardless of the better conception rates, though better conception does help.

Repeats

Looking at heat detection of returns does not show the same link. Efficiency of heat detection for repeat services is not as closely related to better herd fertility.

 

The importance of efficiently serving the cow for the first time is much more important at driving herd performance than detecting returns or conception rate. This may be true now with better conception rates being seen. First attempt is becoming more important than ‘lots of attempts’.

 

The message is to keep your eye on the KPIs that make the difference and those you can manage more easily – serve cows on time. This may be only one veterinary practice’s findings for its own herds, but as at our KPI meeting there is a lot to talk about and possibly be optimistic for the future.

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