Most farmers are settled into seasonal work at this stage with the breeding season well under way. Submission rates this year have been very good.

In truth, submission rates are rarely a problem or cause for herd infertility. The two most common problems are poor heat detection or poor body condition scores.

Most cows presented for scanning that have not been seen bulling have, in fact, have had silent heats.

On a scan, these cows will have a corpus luteum (CL), which is what’s left behind in the ovary after an egg has been released.

Fewer cows will have small inactive ovaries, which in the majority of cases are due to cows being too thin, which can be readily diagnosed.

Conception rates this year have been better than in most recent years. Forage supply, be it grass or silage, has been in good supply for the last 12 months, since the heatwave of June 2013.

The residual effect of this is now being seen in good reproductive performance. Also, since the fodder crisis, more farmers see the benefit of feeding cows beyond the minimum amounts recommended.

This has allowed cows to carry better reserves of body condition throughout the year, which helps carry them through times of stress or variable feed quality.

Despite all this, there have still been problems cropping up from time to time. Cows had very loose dung this May, probably worse than years past.

While this cleared up with diet buffers etc., some of the side effects, i.e. cows repeating, are only now being seen.

I would have seen more cases of grass tetany of magnesium deficiency syndrome this May than for any time in the last 10 years or so.

Every year, one of the greatest challenges cows’ metabolism faces is the variation in dietary intake from mid-March to mid-May.

During this time, they come off an indoor silage-based diet through to a grass diet with high moisture content and then onto grass, which may be getting quite strong by June.

This variation in diet, while difficult to measure, can have variable knock-on effects in some herds in terms of performance, yield and conception rates.

There are three things one can do to help mitigate these undesirable side effects:

Feed magnesium

Magnesium is involved in more than 300 biochemical reactions in the body. It’s just not tetany alone that magnesium supplementation prevents.

Around the world, it’s not uncommon to find dairy cows getting daily magnesium supplementation, even though they are housed all-year long.

Feed maize

Maize can be an excellent buffer that can be a fine complement to the type of grass that cows graze in the second rotation in particular.

Feed meal

While good grass can be the complete food, it is too often variable in content. Meal supplementation in the early breeding season can greatly assist in attaining good reproductive performance.

In all cases, it’s important to talk to your vet for advice on these matters. For most herds, nutrition is probably the most important determinant of reproductive performance.

*Michael Sexton works in Riverview Vet Clinic, a 10-vet practice in Bandon, Co Cork.