The clock is ticking for those cows that calve in late March and April and are expected to go back in calf in May or June. What should you do – leave them alone or intervene?

Many farms are three weeks into the breeding season and at this stage 70% to 80% of the herd has been bred once. The 20% to 30% of the herd that has not been bred consists of the problem cows that have had a hard calving, a problem after calving, or those that calved late.

A number of farmers will get this proportion of the herd handled at this stage in the season to determine exactly where this subset of cows is at. If they need a washing out many will complete that. If a more intensive antibiotic- and hormone-based treatment is required, many will prefer to wait and see rather than set a protocol in place that involves numerous injections and drug purchase.

The argument many farmers make for intervening is based on numbers – if they are short on replacements or want to cull cows for other reasons, then they make a case for intervening and trying to get late-calving cows to cycle sooner and hopefully go in-calf. They maintain the €40 to €50 per cow you spend now on getting late calvers in-calf will be returned threefold in more milk earlier next year.

If you are going down this road, then it is better to do it now at this stage in the season rather than waiting for week nine or 10 of breeding when a late calver will remain very much a late calver or may even miss out completely and not go back in-calf.

Those in favour of the wait-and-see approach suggest the success rate on hormone-induced heats is poor and sometimes all you can do is throw the natural cycle of the cow out of tune. They make the case that it can get very complicated quickly and can take a lot of organising and minding at the expense of other more important jobs.

Instead, farmers might be better served accepting these cows are not going to be served to AI for replacements in the first four weeks of the breeding season and breed them to a clean-up beef sire because you don’t want replacements from poor-fertility cows. They also suggest other options like putting this subset of cows on once-a-day milking or just washing out a cow to help induce a heat cycle earlier at much lower cost and complication.

Previous research indicated leaving late calvers alone once they are clean, and in time they will come into heat and you can successfully breed them.

Moorepark has carried out a number of trials with different methods and to varying levels of success. The most recent large-scale research trial involved a timed AI programme for cows, not just late-calving cows. It involved using hormones GNRH, prostaglandin and a progesterone device such as a PRID.

The programme involved the following:

  • Day one: GNRH (1), PRID inserted.
  • Days two to seven: do nothing.
  • Day eight: take out PRID and inject prostaglandin.
  • Day nine: do nothing.
  • Day 10: GNRH.
  • Day 11: timed AI.
  • Other farmers will just give a blanket shot of prostaglandin to the cows not seen bulling after the first three weeks of breeding or heat detection. Depending on where the cows are in their cycle, between one-third and half of the injected cows should come into heat two to five days after the injection. The cows that didn’t come bulling can then be injected again, 10 to 11 days later, and most of these should come into heat after this shot. However, prostaglandin will only work on cows that are cycling, not on cows that are not cycling or cows with cysts.

    Results published in 2013 show that over 1,500 milking cows in eight herds were used to evaluate synchronization treatments. Within each herd, cows were divided into three calving groups based on calving date:

  • 1,250 ‘‘early’’ calvers more than seven weeks calved at mating start date.
  • 180 ‘‘mid’’ calvers which were between three and six weeks calved at mating start date.
  • 115 ‘‘late’’ calvers which were less than three weeks calved at the mating start date.
  • Cows in the early, mid, and late-calving groups were synchronised. Cows in each of the groups were assigned to one of four treatments.

  • Treatment one: eight-day CIDR and GnRH, PGF2 and AI at observed heat.
  • Treatment two: same as treatment one, but GnRH 36 hours after CIDR out and timed AI 18 hours later.
  • Treatment three: no CIDR (ie Ovsynch).
  • Treatment four: untreated.
  • Among other results, the trial showed:

  • Cows calved less than 10 weeks treated with treatments one or two had increased likelihood of conceiving at first service compared with animals treated with Ovsynch (treatment three).
  • There were only minimal differences in actual pregnancy rates between treatments one and two in cows calved less than 10 weeks, both of which were superior to treatment three (Ovsynch).
  • Thin cows in treatment one had an increased likelihood of conceiving at first service compared with thin cows in any other treatment or untreated cows.
  • The advantage of just using prostaglandin is that at around €3.50 to €4/shot, it is a lower-cost option, even if 50% will need a second shot.

    The other saving is that they are not paying someone to scan their cows. But the downside is that by not scanning they are not identifying the cows with cysts or the non-cyclers that need a CIDR or a PRID. Without treatment, these cows will probably drop out of the system. But many farmers will argue that these cows are probably better off out of the system anyway.

    A hormone-free approach that some farmers find effective is to handle the non-cycling cows but don’t use any injections or hormones. Just handle the cow like the AI technician does and have a feel around and massage the cervix and ovaries.

    This approach has been proven in research trials to have a positive effect as a proportion of the cows will come on heat after being handled.

    Of course, only cows calved for more than 30 days are suitable for any hormone treatment. So hormones won’t solve the problem of cows calved in the last month. These cows need time before any intervention, if indeed intervention should be considered at all.

    What to do with these cows is less prescriptive. Some farmers will put them on once-a-day milking to reduce their BCS loss post-calving and reduce their period of negative energy balance, in the hope that they will come into heat quicker.

    Larger herds

    Some farmers with larger herds who can justify a second herd of cows will run these cows alongside any lame or other problem cows and milk them once a day with a bull running with them. They won’t use any AI on these cows as they don’t want to breed from them.

    The fact that they are being milked once a day and running with a bull should help to return the cow to cycling faster.

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