Farm Ireland

Wednesday 21 March 2018

Keep track of target weight for in-calf heifers

John Donworth

With all the talk about trying to keep grass ahead of cows, or even trying to keep cows at grass, one group of animals has slipped way down the pecking order. These are the one- to two-year-olds, or the breeding heifers that are all in calf at this stage. This group of valuable stock has really been pushed into the background as attention has been totally focused on trying to keep the cows' performance from collapsing.

On a large number of dairy farms, one- to two-year-old stock were rehoused at some point in the months of June and July. Indeed, dealing with this issue with some discussion groups, between half to three-quarters of group members had one to two-year-olds housed.

If the heifers were on the milking block, the decision to house them became an easy one.

What is the knock-on effect of housing in-calf heifers? Well, the major one is weight gain. Will these animals continue to hit their target weights? Remember, heifers that are under weight at calving, remain light as cows.

They milk less (approximately 31kg MS) in subsequent lactations. Calving date also dis-improves, which means some of them don't go in-calf to the first straw.

So, what is to be done? Like a number of things in farming, if you can measure it, then you can do something about it. But first, what are the benchmark weights which you can measure your animals against (see table below).

This table clearly spells out the target weights for the various months of the animal's life. Holstein Friesian in-calf heifers should weigh 450kg at 19 months of age, on September 1. New Zealand/British Friesian in-calf heifers should weigh 425kg, while the Jersey Friesian in-calf heifers should weigh 390kg.

In-calf heifers at grass gain approximately 0.7kg per day throughout the mid-season months. This is the minimum required and with excellent grass, the weight gain will be higher. But grass quality in June and July has been anything but excellent and the weight gain mentioned above might have been difficult to achieve.

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But, on a number of farms, in-calf heifers were housed. Weight gain on silage only is, at best, 0.5kg per day.

So, housed in-calf heifers need concentrates, probably about 1.5kg/day to ensure half-decent weight gain.

The table is telling us that Holstein Freisian in-calf heifers should be 450kg on Spetember 1. Working back, with growth rates on grass of 0.7kg/day, she should be about 430kg on August 1.

If she is well back from that figure, then something will have to be done. She will need 1.5kg of concentrates to ensure lost ground is made up.

Grass quality will also play a big role here and only excellent quality will do.

If in-calf heifers have lost ground in June and July, then the earlier you take corrective action the better.

In 2009 Emer Kennedy in Moorepark introduced 1.5 kg of concentrates to weanlings from August 21 to November 3. These weanlings achieved a growth rate of 0.88kg per day. Similar stock that received no concentrates achieved a growth rate of 0.68kg per day.

The difference in daily liveweight gains resulted in an additional 15kg over the period.

I have said nothing about calves in this piece, but they are equally important. Their target weights are included in the table.

John Donworth is a Teagasc dairy specialist based in Co Limerick

Indo Farming

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