Replacement heifers represent the most valuable resource within any dairy farming business. Invariably, they constitute the most advanced source of genetics within herds and will have the ability to drive the business as a whole forward once they join the milking group.

Throw in the challenge of calving these animals for the first time at 24 months and it becomes obvious that the heifer rearing practises followed on every dairy farm must reflect both the needs of the animals and the drive to improving the efficiency levels within the business as a whole.

With grass growth rates now at peak levels, there is an obvious attraction to get youngstock out to grass. In the past this might have entailed farmers putting heifers on an out farm and essentially forgetting about them until the autumn.

But, according to United Feeds’ nutritionist Bobby Irwin, this is a fundamentally flawed approach particularly where young weanling  heifers are concerned.

“Weanling calves less than five to six months of age should not be put out to grass at all,” he stressed.

“They are neither old enough nor robust enough to cope with the change in moving from a controlled environment to the outdoors and the vagaries of a Northern Irish summer.

“The bottom line in terms of heifer rearing is to ensure that the animals are achieving growth rates of 0.8 kilos of liveweight per kilo per day. This will ensure that they will reach a bulling weight of 390 to 400 kilos at 15 months of age and a calving weight of 600 kilos at 24 months.

“Weaning heifers less than 6 months of age are directing a higher proportion of their feed intakes towards growth, than is the case with older animals. In the event of these young animals going to grass and encountering a bad spell of weather, something that is not unknown to happen in this part of the world, feed intakes will drop off dramatically and the likelihood of them reaching a 24 month calving date could be reduced significantly.”

Bobby Irwin went in to point out that calves old enough to graze should be put out into the most sheltered fields on the farm with grass covers in the region of 2700 kilos of dry matter per hectare.

“They should also be closely monitored in the weeks directly after turnout,” he added.

“Spells of bad weather plus the change from a controlled indoor diet to one with a high content of grazed grass will put calves under a degree of stress, even in cases where the nutritional value of the grazed grass is far superior to that of the forages they were offered indoors. So farmers should be on the lookout for scour problems occurring in the days and weeks post turnout.

“Ensuring that weanlings have adequate access to fresh water is also important. Farmers sometimes make the mistake and assume that weanling calves can access water from the large drinking troughs that are more suited to mature cows,” he explained

“The golden rule is to check that heifers are physically able to drink from the troughs in the fields they are grazing. If this is not the case, then alternative arrangements should be made.

“Key to ensuring the maintenance of the required daily growth rates is the feeding of supplementary concentrates during that first season at grass. Offering 2 to 3 kilos per head per day of heifer rearing  nuts is recommended, according to grass quality and quantity.

“Farmers can discuss specific feeding rates with their United Feeds’ advisor. Offering concentrates in this way will ensure that young heifers will met their required growth rates. Moreover, this approach will also ensure that the young animals are in a state of positive energy balance.

“This, in turn, will allow them cope more effectively with the various parasite and disease pressures which they will encounter over the course of a grazing season.”

The United Feeds’ nutritionist also confirmed that effective grass budgeting is as important with young heifers as is the case with the milking group on a dairy farm.

“Most dairy farmers have no option but to set stock their replacement heifers. However, it is vitally important to ensure that these young animals have sufficient forage in their diets at all times,” he stressed.

So what is the approach to be taken if grass supplies start to run tight?

“In these circumstances, farmers should buffer feed silage or good quality hay. There may also be a requirement to up feeding levels at such times, so as to ensure growth rate targets continue to be achieved,” Bobby continued.

“There is also merit in buffer feeding hay and silage to young calves directly after turnout so as to ensure that digestive upsets are minimised.”

He concluded: “Grass growth rates peaked at between 80 and 90 kilos of dry matter per hectare per day in Northern Ireland this year. These figures can be expected to drop back to between 60 and 65 kilos during the summer months. But the good news is that grass growth rates to date this year have been far superior to those recorded  in 2013.

“It all adds up to a good news story for those farmers wishing to get the best possible growth rates from their weanling heifers this year. Grazed grass is by far the cheapest feed available to farmers, but it is a resource that must be managed effectively.

“Heifers going out for their second season at grass pose less of a management problem for milk producers. They are much hardier and can deal with the vagaries of our climate and the changes in grazing conditions that will confront them.”