ALTHOUGH managing fert-ility of the dairy herd is an all year round job, taking your eye off the ball at this time of year can have a significant knock-on effect.
For example, an 8,000 litre cow that should be calving in February next year must become pregnant in May this year. If this pregnancy is delayed the cow will either be in late lactation or dry next February when she should be on target to reach peak milk production.
Having an extended calving interval like this will not only impact milk yields but also cash flow and additional costs to the dairy farm business.
Research highlights that herd fertility begins in late lactation with the aim of getting cows to a body condition score of 2.75 at drying off and maintaining this throughout the dry period.
Mineral nutrition of the cow is critically important during the dry period. Low calcium and potassium diets can help on some farms to reduce clinical and subclinical milk fever, retained foetal membranes and endometritis leading to poor fertility in the next lactation.
On many farms sire selection will have been completed during autumn with heat detection and service being carried out throughout winter. Pregnancy diagnosis results should be used to inform cull decisions, as cows not in-calf by 85 to 100 days in milk will quickly impact on a herd’s seasonality of production and profit.
The challenge at this time of year is managing fertility at grass and deciding which cows should be let out to graze. Certainly for the highest yielders, consistent energy and protein intakes are essential during the breeding period.
If you have enough high yielders within the herd to justify, these should be batched separately and housed full or part-time to ensure consistency of diet, balanced protein and high energy intakes through the breeding period. Not only will this maintain milk yields but also reduce issues around fertility.
Heat detection in grazing cows:
The key to managing fertility and reducing calving interval is heat detection. Even when cows are turned out to graze, breeding management routines should con-tinue.
Bryan Graham, who farms in Moorfields, Ballymena, installed a ‘cow-manager’ heat detection system four years ago. This ear tag technology, which works off aerials around the cow housing, pro-vides a wide range of information, including fertility, cows on heat, possible infection and
Bryan is able to access this information from the interface, which is very flex-ible for
him. All calvings, fertility and health events are kept up-to-date, meaning that any reports generated provide full and accurate information.
From the information provided, Bryan is made aware of cows that are not yet ready for service, those more than 42 or 60 days calved but not yet served, those potentially on heat
in the next few days based on previous heats and services, and those ready for pregnancy diagnosis.
Research from AFBI Hillsborough shows there is no benefit in delaying first service beyond a 42 day voluntary waiting period as far as conception rates are concerned.
Within the first year of installing the system Bryan was able to reduce his calving interval by 23 days. He puts this down to knowing exactly when cows are coming in heat so they can be AI’d just as they’re going off heat.
Furthermore, of the first 36 cows AI’d after the system was installed, 28 cows held on first service, which was a significant improvement for the farm. Having more detailed information on rumination and infection within the herd has also contributed to improving fertility and as a result been a major financial saving for the herd.
As spring and early summer are a busy time for dairy farmers, the key is to have a system in place which will provide information required to manage fertility and detect cows in heat.
Particularly when cows are at grass and when attention may be focused on other jobs on the farm, a simple heat detection system can prove vital in ensuring that fertility of the dairy herd is not negatively impacted at this time of year. By giving focus to fertility now, the opportunity presents itself to improve cash flow in nine months’ time.