Split block-calving businesses can soon erode the efficiencies gained from calving in both spring and autumn when cows are allowed to slip between the two blocks.
Despite current cull prices and rising replacement costs, carrying cows over – whether in the same herd or to a separate herd – will lose money.
Every time a cow slips, three months are lost before she gets to the next block, says vet Rachel Risdon of Westpoint Vet Group, Cornwall.
“This is more than in a year-round calving herd, where a cow would slip just three weeks (one cycle). In addition, some cows may not milk on for an extra six months, so they may have to be dried off with their original group before transferring blocks. But this produces an extra-long dry period, with cows liable to get fat. Or, you end up in a situation with one or two lonesome dry cows that don’t fit either block.”
Difficult calvings, endometritis and anoestrus make it harder for cows to get pregnant again on time. But late-calving cows and first-lactation heifers often struggle, too. Calving at the tail end of a 12-week block, cows have fewer chances to get back in-calf during the planned mating period. While heifers must cope with the stresses of herd life.
Although late calvers can be induced, there are risks, says Mrs Risdon. Using steroids to calve early can knock the cow’s immune system and lead to health issues such as more mastitis. Instead, she recommends a vet check to make sure all cows are clean and cycling before mating, working back from the planned start of mating.
“Cystic or anoestrus cows can be treated. Another option is the ‘why wait?’ system, where prostaglandin is used to shorten oestrus cycles. It brings cows forward by a week, concentrating three weeks of AI into two weeks.”
Mrs Risdon believes hormone therapy is more cost-effective than allowing cows to slip between groups when done at the right time. “Depending on the number of replacements coming in, it may also be better to sell individuals rather than carry them over,” she adds.
Where a cow is carried over to the next block, Mrs Risdon suggests fitting her with a sheep ear-tag. This acts as a visible and permanent reminder that this cow has had her chance – and next time needs appropriate action. She also reminds producers that it is always better to improve fertility by managing cows to ensure they calve down in the correct body condition.
“Fertility is related to condition score at calving: The right score leads to fewer non-cycling, or dirty cows. Plan ahead and manage condition score two months before drying off. After calving, record all heats and identify at-risk cows that might have trouble getting back in calf on time.”
TONY RENWICK, EAST SUSSEX
Herd manager Tony Renwick is synchronising heifers and cows to front-end load an autumn block calving. This ensures that 86% of Lord Newton’s 230-cow herd calves within the first six weeks.
Having first converted the herd at Arches Farm, East Sussex, from year-round calving and high yields, Mr Renwick’s goal is now to have all cows calved in six weeks. “We want to fill the bulk tank as quickly as we can,” he says.
Autumn block calving means cows are dry when grass growth stops in summer and supply winter milk, worth up to 6p/litre in seasonality payments. But a tight calving pattern is also important for what is basically a one-man system plus it creates a neater block of heifers to rear and calve together, he adds.
Last year, Mr Renwick tried inducing some late-calving cows to give them longer to get pregnant again. “They all held their cleansing, even though we prepared them with selenium and vitamin E jabs. We had to wash them all out and each was served two or three times,” he says.
Instead, working with his vet Steve Blowey of Howe, Starnes, Gatwood, Blowey and Wood, he uses prostaglandin so that cows and heifers are bulling and ready to be inseminated on days one and two of the mating period. “Calving early in the block, this gives a heifer 12 weeks in which to become settled into the herd and milking routine, and get cleaned up ready for serving.”
Tony says the cost of synchronising (including vet time) works out at £5.10 a cow and £14.50 a heifer. The herd now has a 21-day submission rate of 95% and a 12-week empty rate of 7%.
Slipping cows between block calving
- Lose three months
- Long dry periods
- Front-end load the block