Liveweight Targets

Liveweight at first mating and calving will have an impact on the reproductive performance and milk production potential of heifers.

Heifers must be reared to achieve their liveweight targets otherwise their first calving will be delayed, liveweight at calving will be too low and fertility during the next mating period reduced. Well-grown heifers will produce more milk in the first lactation, compete better with mature cows and survive longer in the herd.

Having targets offers a measure of performance and indicates well-grown stock. Targets also establish an agreed position for farmers involved in a contract grazing relationship.

Heifer liveweight targets

30% of mature weight at 6 months of age
60% of mature weight at 15 months (mating)
90% of mature weight at 22 months (pre-calving)

Because body weight is the key driver of puberty it is important that heifers reach key liveweight targets if they are going to reach puberty at 12 months and get in-calf at 15 months.

Achieving the 30-60-90 percentage targets is more important than the pattern of growth.

Heifer development plan

Meeting heifer weight-for-age targets should be the focus rather than a particular pattern of growth. To meet targets, heifers need to grow at appropriate rates over two years; putting a plan in place will help to achieve this.

Use this tool to set a plan for the first two years of a heifer's life. Set expectations for the animals weights, feeding levels and animal health requirements. Use with your grazier to set expectations and check your heifers' progress.

Heifer Development Plan

Estimating mature liveweight

There are three methods to estimate average mature liveweights for a group of heifers: liveweight breeding value, weighing a selection of mature cows (6-8 years of age), and using a breed-based average mature weight.

Liveweight breeding value (Lwt BV)

Obtain a 'breeding value trait report' from your herd recording provider (e.g. CRV, LIC). From this report calculate the average Lwt BV using the following equation:

Mature liveweight = 503kg* ± Lwt BV

If the BV is +20, then the average mature target liveweight for a group of heifers will be 503kg* + 20 = 523kg
If the BV is -15, then the average mature target liveweight for a group of heifers will be 503kg* - 15 = 488kg

* Based on base cow liveweight of 503kg.

Strengths	Weaknesses
Objective measure	An on farm study showed that 30% of animals were not matched to the correct mother
Best prediction based on an animal’s genetics	Genes are randomly inherited
Based on actual data from sire proving herds	Normal variation is -5% to +5% of the prediction
Accounts for current breeding program targets	Liveweight is 35% heritable so management has more influence on the final result
Majority of animals will have a Lwt BV	Currently only available through MINDA software
	Data will not be available for herds with a high proportion of overseas genetics

Mature herd average weight

Average herd liveweight can be determined by weighing a cross section of the mature herd. Weighing guidelines to establish the target are:

20–50 cows (the more you weigh the more accurate)
6-8 years of age
100-200 days in milk
BCS 4.5 (add or subtract weight if above or below)
After the morning milking

This information can be used to validate Lwt BVs and will be most accurate for herds with consistent breeding strategies and limited breed variation within the herd.

Strengths	Weaknesses
Representative of actual herd	Time required
Data will not be available for herds with a high proportion of overseas genetics	Not every animal will represent “average”
Improves information for the herd (e.g. stocking rates, drench rates, mineral dosing)	Does not capture recent changes in breeding policies (e.g. increasing crossbreeding)
Captures management and environmental conditions of the farm system	Will set targets too low if mature stock were poorly grown

Average mature liveweight based on breed

Determine the average mature liveweight of your heifers based on herd composition, using the table below.

Breed	Weight
Jersey	410 kg
Crossbred	482 kg
Friesian	524 kg

Source: New Zealand Dairy Statistics (2022-23)

As these mature weights are the average of the population, groups of heifers of a comparative breed can have targets above the average mature weight. Weight gain records and physical observations should also be used to evaluate the average mature weight when applied to a group of heifers. Based on base cow liveweight of 503kg.

Setting weight-for-age targets

Weight for age targets should be used for mobs. The average weight of a mob should meet each target weight-for-age, this will indicate that they are on track for meeting the 22-month target.

Individual heifer weights will fall on either side of the weight-for-age target. It is natural to have variation in a mob, and studies have shown that some healthy heifers may be 15% lighter than their peers.

Breed average mature liveweights and weight-for-age targets

Weight-for-age targets (highlighted) for animals of different mature liveweights, with guide weights for other ages.

Mature weight	Age	Liveweight (kg)
100%	6 - 8 yrs	420	465	500	550	600
20%	3 months	84	93	100	110	120
30%	6 months	126	140	150	165	180
40%	9 months	168	186	200	220	240
50%	12 months	210	232	250	275	300
60%	15 months	252	279	300	330	360
80%	19 months	336	372	400	440	480
90%	22 months	378	419	450	495	540

Before heifers move properties, the group should meet their target weight-for-age. The number of animals below target and/or the range around the target should be documented, particularly in contract grazing situations.

Monitoring performance

Most dairy farmers and farm advisers can recognise whether heifers are in good or poor condition, but few can judge whether heifers have actually achieved target liveweights for their particular age.

Weighing heifers on a regular basis provides an 'accurate' assessment of how well heifers are growing compared to targets. It also allows for proactive management - if heifers are under target at weighing, remedial action can be taken to get them back on track. Find out more about heifer feeding and nutrition.

There is no strict rule about how often heifers should be weighed (InCalf recommends every 3 months). The more frequently heifers are weighed the more quickly a problem will be detected. Find out more about heifer weights and weighing.

Use in farm management decisions

Establishing heifer liveweight targets, and the growth required to meet them will aid farm management decision-making. The information can be used when answering a range of questions, including:

If a farm grows 10 tonnes DM/ha what is the best stocking rate?
What is the most efficient nitrogen policy?
How much supplement is required, either made or purchased?
What crops would be most suitable when pasture availability is limiting?
What factors could make attaining the required heifer weight gain challenging?

Liveweight targets can give you a better understanding of what the cost of growing heifers is going to be, which can then be used to assess the costs and benefits of using land for heifer grazing, to decide whether to purchase or lease land and to negotiate a fair price. They are a valuable tool to use when reviewing heifer management. Final weights can be compared with targets to identify missed opportunities and review costs. Targets can also be used to set minimum weights, establish rejection criteria, or prompt early culling.