What targets must be met in order to secure reproductive success for a block-calving dairy system?
The aim of block calving dairy herds, particularly spring-calving herds, is to maximise margin from a low input, low output system. Vet Dave Gilbert, of Dairy Insight, says one of the key focuses is always forage utilisation; matching the demand for feed to the grazed grass growth curve, making sure the system is running as efficiently as possible.
He says: “Grass growth and fertility are the key engines which drive your business, grow the grass and get the cows in-calf to convert the grass into a saleable product.
“Making sure tasks such as calving and service are tightly concertinaed together is really important to maximise results.”
He says this year’s fertility has huge implications on next year’s fertility and future performance throughout lactation. And adds there are huge gains to be made by taking steps to maximise fertility.
“Cows which calve earlier in the block have more time to recover before the planned start of mating which is better for their subsequent reproductive performance.”
Unlike all-year-round calving herds, block calving herds are not working to an individual voluntary waiting period before mating, instead the planned start of mating is the same for all the cows in the herd, irrespective of the date they calved in the block. This means the earlier the cow calves the longer it has to recover.
For every day later a cow calves in the block, it is 0.5 per cent less likely to be back in-calf by six weeks into the next mating period.
One important metric used to gauge performance in block calving herds is the six-week in-calf rate, this is the percentage of cows which are in-calf by the six-week mark of the service period.
Mr Gilbert explains that for every 1 per cent improvement in in-calf rate, there is a £5-£6 return per cow in your herd. So for a 300-cow herd and a 1 per cent improvement in six-week in-calf rate there is the potential of a £1,500 return.
The target submission rate for a block calving herd should be 90 per cent, says Mr Gilbert, which is higher than in an all-year-round calving herd, and a target conception rate of 60 per cent should be put in place.
Mr Gilbert says: “Calving pattern is the number one driver of this year’s fertility performance, there is nothing you can do about it; it is retrospective. So we need to think about that and focus on other areas to drive performance into the following year.
Mr Gilbert sets out his five non-negotiables to meet the key performance indicators which should be targeted by block calving herds.
Mr Gilbert says the best way to manage early lactation body condition, if you are working towards a tight calving block, is to have the cows in the right BCS at calving.
He says: “To do this you need them in the right BCS at drying off, if they are to be in the right BCS at drying off you need to start working on BCS at about 200 days in-milk.
“Once you have pregnancy diagnosed the cows, look at the status of your herd and work towards your target for dry off.
“This is a critical step to manage the energy status of the cows in early lactation and ensure they are fit and able to hit both those challenging 90 per cent submission rate targets and also the challenging 60 per cent conception rate targets. If we have thin cows we will struggle to deliver those.”
“It should not come as a surprise to anyone that healthy cows get back in-calf. Ensure vaccination protocols are in place to minimise the risk of infectious disease and be sure to carry out post-calving checks.
Mr Gilbert says much the same as in an all-year-round calving herd, cows need to be healthy and ready to go on day one of the service period.
He says: “Do not assume your cows are clean, uterine infections are common. In the herds I deal with, even though we work hard to ensure cows are in good condition at calving to minimise milk fever we still expect to see up to one-in-five cows dirty post-calving. Those infections can halve your subsequent six-week in-calf rate if you do not do anything about them.”
Mr Gilbert advises putting a plan in place and work with your vet to routinely find cows with endometritis and treat them.
Mr Gilbert says: “Everyone has a plan, but in any given year depending on how thin the cows are, how difficult winter was or what the prevailing environmental conditions are like you might find heat detection is easier or more difficult. Really it is a question of tailoring the amount of effort we go to, to find bulling cows to achieve our targets.”
In order to reach the 90 per cent 21-day submission rate, on the basis some cows will have an inter-oestrus interval longer than 21 days and will naturally not come bulling within that 21-day period, Mr Gilbert says it is important all the cows are cycling. And every cow in heat during that 21-day period needs to be served to achieve the target.
Mr Gilbert says: “Certainly in the block calving herds I deal with, everyone understands the importance of heat detection and finding all the cows bulling, but the area we are struggling with is usually conception rate.”
He says a lot of people are starting to scrutinise the handling of semen and, in particular, sexed semen.
“We really need to look after that sexed semen to get the best results we can out of it. Poor handling of semen has a knock-on effect on conception rates and you do not have the room for that if you are going to run a tight efficient system.”
Mr Gilbert says if you are going to manage an aspect of your business you must measure it. He says this is more critical in a block calving system than any other.
He says: “We know what our KPIs are. We need to break them down into daily targets. For example, a daily service target, constantly review the numbers, adjust and react to what is in front of us.
“In a block calving system by the time six weeks of the service period have passed and cows have been scanned and you have found they are not in-calf it is too late. The block is almost over. You need to have the lead indicators in place and react to what is going on.”