Farm Ireland
Independent.ie

Monday 12 November 2018

Dan Ryan: Identify cows that aren't fit to breed - and earmark them for culling

 

Dan Ryan

Dan Ryan

This has been an extremely difficult season to date. Grazing conditions and indeed the opportunity for zero grazing have been challenging.

However, those farmers who have maintained supplemental concentrates to avoid a continuity of negative energy balance and, in turn, maintain optimal body condition scores are reaping the rewards of high submission rates and pregnancy rates of close to 50pc to the first AI.

Our experience from whole herd pre-breed scans, using the smart scan technology, has revealed that first lactation cows are losing too much BCS in the first six weeks post calving. These cows are faced with either an anoestrus or a deep anoestrus state when the breeding season begins.

Basically, these cows are not cycling. The use of synchronisation programmes to induce heats in those cows will meet with very poor success as the cows are not fit to be bred.

There is a lesson to be learned here for the future management of our first lactation cows. These animals need to calve down having achieved an optimal weight at calving. The risks associated with competition for both rest areas and feed space have to be avoided.

Considering the costs of introducing these first lactation animals to the herd, it is unquestionably foolish to cull them after their first lactation because of poor first cow transition management.

Late-calving cows have been neglected on many farms. This has resulted in a high incidence of milk fever, ketosis and displaced stomachs.

Pre-breed scans in these cows have revealed a high incidence of post-calving uterine infections. These are not simply rectified by a uterine wash-out. These late calvers will require immediate veterinary attention to give them an opportunity of showing heat and going in calf.

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Heat detection or submission rates have been poor on many farms. This has been associated with both the previous experience of dry cow/fresh cow transition periods, and poor grazing conditions with wet weather and cold nights.

At this stage of your breeding programme you should have a picture describing those cows not yet detected in heat and having potential reproductive disorders.

These cows need to be presented for scanning with the required veterinary attention to get these animals bred successfully.

Indeed, this sub-group of the herd will contain cows not suitable for breeding. It is important that these cows are identified and earmarked for culling from the herd.

Heat detection in maiden heifers has been difficult this year. Many farmers have used controlled breeding programmes to synchronise heifers for breeding on a given date. This will work successfully if the heifers are fit for breeding.

However, we have encountered where maiden heifers may have achieved target weights for breeding but are in a deep pre-pubertal state and will not be bred successfully this year. This has been associated with confinement stress and overcrowding, with an extended winter period and poor-quality silages.

A major challenge facing many farmers with large dairy herds is the walking distances required to graze grass on remote areas of the grazing platform.

Forcing cows to walk distances of 2km per day or more will result in welfare issues such as lameness and the associated metabolic load will reduce milk production by up to three litres per cow per day.

As grazing conditions improve, farmers will dramatically reduce the supplementation of concentrates in the diet.

This may make economic sense in the short term but caution has to be exercised that reproductive performance will not be impaired because this dictates the future survivability of the herd. Grazed grass is not a balanced diet that meets the cow's requirements to optimise both health and reproductive performance.

With the advent of climate change we will need to have reserves of silage to meet the needs of our cows during either extended winter periods or poor grazing conditions during the summer months.

Dr Dan Ryan is a bovine reproductive physiologist and can be contacted at www.reprodoc.ie


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