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 |
536kg |
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.