How to manage turnout of youngstock for optimum intakes

When dairy youngstock are turned out this spring, the transition from winter feed to grass probably represents the most abrupt change in management and diet these animals will have experienced.

This is particularly the case if this is the first time they have seen grass and could lead to a check in growth. But this must be avoided if the target 24-month calving at 85% of mature weight is to be met.

When moving from a diet of relatively high dry matter (DM) haylage or silage to lush, spring, low-DM pasture, a close watch needs to be kept on grass quality and intakes, as well as the animal’s growth.

See also: Calving age and forage quality key to lower dairy emissions

First-year heifers

“This is all the more important in first-year [R1] heifers, whose rumens will not have developed if they are less than five months old,” says Chris Coxon, from the Tiller Farm Consultancy.

“Add to this the fact that the animals are growing and need a slightly higher intake of grass every day of their life, and the challenges mount.”

Nowhere is this challenge greater than in heifers aged less than nine months. They have the highest energy density and protein requirement of all youngstock.

“This is the age group I’m most concerned about,” says Mr Coxon. “Post-weaning 120kg calves need a dry matter intake [DMI] of 3kg. On typical early spring grass of 17% DM, this means consuming 18kg of fresh grass.”

With a feed conversion ratio at this stage of roughly 3:1, this intake results in the required growth rate of about 1kg/day.

“It’s very difficult to achieve this level of DMI from grass in animals aged less than six months, so grazing is a particular challenge in spring-born calves,” he says.

“Most producers feed 1-2kg of concentrates at this time, and I’d suggest considering a high-quality product up to this age.

“This makes the best use of quality feed while the animal has the greatest ability to convert it into growth.

For those keen to graze their spring-born heifer calves early, Mr Coxon says they may as well have the latter period of milk feeding at grass.

“The feed they will turn to eat at weaning is then grass, so this makes the transition to grass more straightforward,” he says.

Monitoring progress

The six-month target is one of the most important to hit. “An easy figure to remember is for roughly 25% of mature weight and 75% of mature height to be reached at this age,” he says.

From six months onwards, costs can be reined back, provided grass quality exceeds a metabolisable energy (ME) of 11MJ/kg DM.

Leader-follower system

Adopting a leader-follower system gives the younger, R1 heifers the pick of the grass. The older, R2s, follow, taking the slightly more stemmy grass.

“The optimum DMI is 2.5% of bodyweight,” says Mr Coxon.

“There’s always a trade-off between maintaining grass quality and animal growth, and this intake has been shown to be optimal.”

Rotationally grazed stock should ideally be moved every day.

This means a paddock would be grazed in two days in a leader-follower system: day one for the R1 “yearling” heifers and day two for the R2 “bulling” heifers. In practice, twice a week is achievable on most farms, suggests Mr Coxon.

Rotational grazing is considered far preferable to set-stocking.

Set-stocking is unlikely to achieve target intakes and growth rates without continued supplementary feeding or an oversupply and wastage of grass.

Where R2 heifers are put on parts of the farm that can’t be reseeded or where the grass is unlikely to hit the required ME of 11MJ/kg DM for much of the season, at least 1kg a head of concentrates may be needed.

However, this can be reduced in quality, to 16% protein in this group.

“The cost of a kilo of cake a day is a lot less than delayed service or calving. Rearing costs can easily hit £50/month when each animal’s feed, labour, bedding and shed space are taken into account,” Mr Coxon says.

He also suggests considering whether heifers could be assigned to higher-quality leys, leaving older or permanent pasture with low MEs for dry cows instead.

Bulling weights

While the pinch point for R1 heifers is achieving growth on grass before the rumen is developed, for the R2 heifers, it is achieving good bulling weights.

This is especially the case for 12-month-old autumn-born calves, as it coincides with a decline in autumn grass quality.

“Feeding concentrates to this group around a month before and after breeding is a good discipline,” he says.

“The energy may be in the grass, but the DM isn’t, and smaller heifers in particular will find it a huge challenge to eat enough.”

Signs to watch

Getting everything right is a huge challenge and requires close and careful monitoring.

By now, heifers should ideally look like “small cows”, particularly in terms of body condition score and rumen fill, says Mr Coxon. There are some warning signs to look out for.

“If they are short, with a big belly, they may not have had enough protein, but if they are tall and skinny, they may have had too much protein, or insufficient energy.”

With a consistently well-balanced diet and a focus on the younger animal while she can convert her feed most efficiently, it is possible to average a growth rate of about 0.75kg/day* between birth and calving.

“This can be achieved from grazing in the growing season, but only with favourable conditions, outstanding grassland management and ideally with a grazing type of animal,” he says.

* The 0.75kg/day growth target from birth to calving is for a heifer that will reach approx 375kg pre-breeding and go on to an adult weight of 685kg. Exact figures will vary with breed and system