Scanning always reveals some surprises
Published 12/08/2015 | 02:30
With quotas no longer a limiting factor, many farmers are considering milking cows into December or indeed throughout the winter months. But it will be milk price that will determine the economics of milking this winter.
Breeding programmes for spring calvers should now be at an end. However, stock bulls are still running with most dairy herds that I visit, and the cows being bred now will calve in mid-May.
The reason for this is that many farmers will not accept culling young cows in first, second or third lactations simply because they are not in-calf by July.
Therefore we will continue to have May and June calves on many grass-based milk production systems.
The first three weeks of August is a 'wait and see' period in the breeding programme. Farmers like to wait for four weeks after the bull has been removed to scan the entire herd for pregnancy status.
But remember that the accuracy of foetal gender determination and identification of cows carrying twins decreases as cows extend beyond three and a half months of pregnancy.
The information harvested from this scan forms the basis of your business for 2016.
Scanning your dairy herd will present many surprises to farmers.
Cows presumed empty on the basis of heat activity will be identified as pregnant.
Conversely, up to 10pc of pregnant cows will show signs of heat - unfortunately many of these cows needlessly end up in the abattoir.
Some of the empty cows that were presumed pregnant cannot present signs of heat because of either a hormonal dysfunction or an embryonic foetal death that leaves the cow in a 'pregnant' state.
The primary occurrence of embryonic foetal death in scans at this time of year is associated with cows carrying twins.
A cow's reproductive tract consists of two uterine horns.
The presence of twins in one uterine horn results in a minimum of a five-fold increase in the risk of foetal death.
These cows will not return to normal heat cycles for up to three months after embryo death.
Having identified empty cows, farmers need to make decisions on the future of these cows.
In strict grass-based systems, these cows should be culled at the end of the grazing season.
Housing capacity maybe at a premium, or it may be considered uneconomic to fatten these cows prior to culling.
Alternatively, farmers will use the scan to identify 'fit' empty cows for recycling into an autumn calving programme or introduction into the 2016 spring breeding programme.
They will need to be free of reproductive abnormalities, high cell counts, bad feet or legs, and have had less than five calves.
Stock bulls are used on the majority of dairy farms after an initial four to seven week AI breeding programme. In our experience, less than 10pc of services associated with pregnancy from a stock bull are recorded.
Dry cow management accounts for approximately 80pc of herd health and reproductive outcomes in the dairy herd.
It is therefore imperative that we have accurate calving dates to ensure that cows experience an optimal nutritional regime for the six-week period pre-calving and two week post-calving period.
Scanning inside the first three and a half months of pregnancy will provide you with this essential information.
Farmers lament when a cow is identified carrying twins. The complications associated with management of these cows are immense.
The increased risk of metabolic diseases, retained afterbirth, poor reproductive survival post calving, and poor survival rates among calves born are all well-known.
The incidence of twins born ranges between 2pc and 10pc on farms. The incidence increases with the age of the cow and the genetic potential for milk production.
The reported incidence is lower than that experienced because farmers do not wish to have inspections from the Department of Agriculture over the incidence of twin births.
This latter problem could be rectified if scan data could be used as supporting evidence to the Department.
Finally, there is a need for preventative health management at this time of year.
Farm visits reveal that body condition scores (BCS) are below target for many cows. This is a worry, given that this is a period when cows should be increasing BCS.
This status is primarily associated with IBR, lungworm, stomach fluke or liver fluke infections. It is essential that you establish your current status using a combination of blood, milk or dung samples.
This is very cost effective in planning for the future dry-cow period.
Dr Dan Ryan is a bovine reproductive physiologist and can be contacted at www.cowsdna.com