Livestock Event 2014: How to reduce your calving interval

It is possible to tighten calving intervals in beef and dairy herds by up to four weeks a cow a year through strategic management and monitoring.

“If you are not in a position to cull really hard and you don’t have a lot of replacements, you can gradually move the calving block back,” vet Helen Rogers from Friars Moor practice, Dorset, told farmers at the Livestock Event.

“It is achievable for a June-calving herd to become a May- or April-calving herd,” she added.

But don’t expect miracles, it’s a slow process, warned Mrs Rogers.

She said a “typical second-calver scenario” was a cow whose calving interval had lapsed to 500 days. These, she said, were the cows that cost farmers both time and money.

Breeding programmes

She said breeding programmes could play a key role in helping to reduce calving intervals within herds. But she said farmers needed to use the most appropriate protocol for their cows.

Ovsynch programmes are not suitable for heifers or beef cows.

“The protocol has to match the length of time the follicle is there to become big enough to respond to the hormone.

“Dairy heifers and beef cows have three follicles developing every 21 days and it is the third that ovulates.

“Cows have two follicles developing and it is the second egg that ovulates,” she explained.

Because the eggs are smaller in beef cows and dairy heifers they are less responsive to gonadotrpin-releasing hormone, so are better suited to progesterone-releasing intravaginal device programmes.

She said if farmers did decide to use a breeding programme it is essential to keep to the recommended timings when administering hormones.

“If you forget to give an injection it is probably best to abandon the whole thing and start again.”

Body condition scoring (BCS)

Poor body condition is a precursor for poor fertility, she warned.

A good BCS beef cow will ovulate the dominant follicle after 20-30 days, but a poor BCS beef cow may not ovulate the dominant follicle until 70 days, she explained.

Therefore, she suggested all herds should run a separate dry-cow group so body condition can be maintained at the correct score in the run-up to calving.

Synchronise heifers

Meanwhile, she advised farmers wishing to tighten their calving interval to calve heifers at the start of the block.

“Synchronise heifers to calve at least two weeks early, because they have the highest genetic potential within the herd.

“Heifers have a lot more to deal with [compared to cows]. They need to join a different social group, grow and carry on rearing their calf, so they need an extra two weeks to recover and for their ovaries to start cycling again.”

She also advised pregnancy diagnosing cattle as early as possible to ensure breeding protocols have worked and prevent extended days open.

“This will allow you to get rid of the cows that you don’t want to carry through the rest of the year.”

Fertility aims

• Beef herds – 65% of your cows should calve in the first three weeks and another 25% in the next three weeks.
• Dairy herds – Pregnancy rates should be 35-40%-plus