Raising Outstanding Dairy Heifers

There is often an air of expectation as we bring a fresh group of dairy heifers into our herd. A lot of time and effort goes into the milk feeding phase of heifer rearing, turning out some outstanding calves at weaning.
Once the heifer calves are weaned and go out to grazing, there is often a sense that the heavy lifting is done. However, to have outstanding dairy heifers entering our herds, we need to ensure that we continually reach target weights and wither height for age and breed at every critical juncture during the first two years of life.

Regular measuring and monitoring

There are multiple calculations that can be used to establish target weights for age and breed. It is important to also establish wither heights for breed, as frame development has strong links with lifetime milk production in dairy heifers. Regularly weigh and measure heifers in order to monitor the progress of your replacements. Remember, you cannot monitor what you have not measured. Replacement heifers should be weighed and measured at a minimum eight-week interval in order to assess the adequacy of their current nutrient intake. Table 1 gives reference target weights and wither height for age, by breed.

Summer pasture challenges

Within grazing systems, one of the most difficult periods to maintain adequate nutrient intake to meet heifer growth objectives is from December through March. Most replacement heifers are grazed on dry land blocks where pasture quality and quantity can become challenged. To realise daily liveweight gains above 0.7kg, summer pasture will need to be supplemented.

As a starting point the ration will need to be balanced for energy, metabolisable protein, calcium and phosphorus. Trace minerals such as copper are essential for bone integrity and should not be overlooked; along with selenium, cobalt and iodine. (Bolus application may be the most applicable method of delivery.)

Table 1: Heifer Growth Chart

Age	Fresian		Jersey		Kiwi X
Months	Weight	Wither height	Weight	Wither height	Weight	Wither height
0 (at birth)	45kg	0.73m	35kg	0.66m	40kg	0.70m
2	85kg	0.84m	65kg	0.76m	76kg	0.81m
4	125kg	0.95m	95kg	0.86m	112kg	0.91m
6	165kg	1.02m	125kg	0.92m	148kg	0.98m
8	205kg	1.08m	155kg	0.98m	184kg	1.04m
10	245kg	1.13m	185kg	1.02m	220kg	1.09m
12	285kg	1.17m	215kg	1.06m	256kg	1.12m
14	325kg	1.20m	245kg	1.09m	292kg	1.16m
16	365kg	1.23m	275kg	1.12m	328kg	1.18m
18	409kg	1.26m	308kg	1.14m	368kg	1.21m
20	452kg	1.28m	340kg	1.16m	406kg	1.23m
22	500kg	1.30m	376kg	1.17m	449kg	1.25m
24	559kg	1.31m	421kg	1.19m	503kg	1.26m
24 (calved)	525kg		395kg		472kg

Following are some examples of how nutrient supply from different rations will influence possible daily gain.

Breed: 6-month old Friesian heifer

Liveweight entering summer: 160kg liveweight (LWT)

Target liveweight: 200kg at 8 months, 500kg post-calving

	Ration 1	Ration 2	Ration 3	Ration 4	Ration 5
Summer pasture	3.7kg/DM	3.0kg/DM	3.0kg/DM	3.0kg/DM	3.0kg/DM
Pasture silage	-	-	-	1.4kg/DM	-
PKM	-	-	1.4kg/DM	-	-
16% Heifer meal	-	-	-	-	-
Total DMI:	3.7kg/DM	3.0kg/DM	4.4kg/DM	4.4kg/DM	4.4kg/DM
ME supplied	37MJ	30MJ	44MJ	44MJ	48MJ
MP supplied	345g	280g	380g	375g	442g
Possible daily gain	0.35kg	0.10kg	0.61kg	0.60kg	0.75kg
Possible LWT @ 8 months	181kg	166kg	196kg	195kg	205kg
Target LWT @ 8 months	205kg	205kg	205kg	205kg	205kg

ME Metabolisable energy MP Metabolisable protein

Observations

Daily grazing intake is calculated at 2.3% of LWT. Total dry
matter intake (DMI) increases to 2.6% of LWT when supplementary feeds are offered (NRC 2001). Low quality summer pasture alone struggles to supply adequate nutrient intake to reach the 8-month 205kg LWT target. It isn’t difficult, however, to provide a supplement that will bridge the gap.
This same principle applies to 18-month old heifers going
into their second summer.

Adjusting for fetal weight

With reference to rising two year olds, our target weights in the final months of gestation must be adjusted to make allowance
for fetal weight; a detail that is often overlooked.

An example

Herd: Friesian

	SCENARIO ONE - no correction for fetal weight	SCENARIO TWO - correction for fetal weight
Mature LWT target	525kg	525kg
Replacement heifer target	475kg 90% mature LWT	577kg 110% mature LWT
Pre-calving weight	475kg	577kg
Post-calving weight	440kg Lost 7% LWT in calving Now only 83% mature LWT target	536kg Lost 7% LWT in calving Safely above mature LWT target

Our example Friesian herd with a target mature LWT of 525kg will want replacement heifers entering the herd at a minimum 475kg (90% of mature LWT). What can be something of a trap is that we weigh our heifers pre-calving and they may meet this target. Yet post-calving we give up around 7% of their LWT, meaning our heifer is now only around 440kg (83% of mature LWT).

For simplicity, it is sound practice to target 110% of mature LWT so that you have already corrected for fetal weight. Alternatively, you may reference a chart (see Table 1) which is corrected for fetal weight. Nutrient intake will clearly need to be increased to allow for growth and pregnancy requirements.

The benefits of well grown heifers

When replacement heifers enter a herd with the same frame development as mature cows, they are capable of producing up to 85% of the mature cow average. This lifts feed conversion efficiency and production across the entire herd. Nutrients ingested are partitioned towards production rather than continued frame growth. These heifers are also under less metabolic stress in their first lactation, positioning them for improved reproductive performance.

Following best practice with your replacement heifers is an investment that has the potential to yield economic benefits
over the lifetime of each animal.

For more information talk to your local Ingham Dairy Nutrition Specialist.