A recent report by George Ramsbottom, a dairy specialist with Teagasc based in Oak Park, Co. Carlow, outlined that almost 390,000 dairy cows (more than one-quarter of spring-calving Irish dairy cows) calved later than April 1 in 2019 and 2020.
George started the report by stating that ”what’s worse is that almost as many calved in May and June as in April”.
”It is challenging enough to breed an April-calving in the first three weeks of the breeding season, and impossible if she calves in May or June.”
Does it matter?
”Absolutely, because achieving a high level of reproductive efficiency in the dairy herd underpins profitability of grass-based milk production,” George said.
”Target submission rates of 90% of cows and 100% of maiden heifers bred in the first three weeks of the breeding season are both desirable and realistic.
”However, the national average in 2019 was only 71% of cows and 78% of heifers bred during this period.
The reproductive cycle of the cow requires a period of rest and recovery before she is able to go back in-calf again.
”Estimates vary, but a rest period of around 30 days after calving is considered the absolute minimum before commencing a treatment programme.
”Cows calving within four weeks of the start of the breeding season warrant special attention to help ensure that they go back in-calf. Later-calving cows are typically in better condition at calving, because they generally have an extended dry period.
Late-calving cows are generally older, higher-yielding cows and thus more prone to rapid body condition loss.
”These cows also tend to be in calf to longer-gestation-length beef bulls and consequently are at greater risk of increased calving difficulty.
”This will in turn delay the resumption of the cycle required to allow them to be bred again.”
George stated that there are two strategies which can shorten the interval between calving and breeding in such cows.
OAD milking
The once-a-day (OAD) milking approach is typically used on low somatic cell count (SCC), late-calving or thin (body condition score (BCS) <2.5) cows.
Using the OAD milking approach, cows typically receive artificial insemination (AI) within 50 days of calving.
The loss in milk yield for a cow milked once a day for 40 to 60 days is approximately €55-75.
Hormonal intervention
The advantage of the programme is that it promotes cyclicity in cows that are not yet naturally cyclic (however they should be 30 or more days calved at the start of the synchronisation treatment), and they can be AI’d at a fixed time regardless of the signs of heat.
Using this approach, late-calving cows are typically batched into groups and AI’d at an average of 45 days after calving. The treatment is approximately €40 per cow, excluding AI cost.