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Mating Weights

Best Practice


What is a Critical Mating Weight?

Critical Mating Weight (CMW) is defined as:

  • the weight at the start of the joining period at which 85% or more heifers will fall pregnant in a 42-day joining period1.

Don't confuse CMW with average weight at puberty and average group weight at mating, both of which are much higher.

CMW should be determined for each herd

Why is it important?

Weight is one of the most significant factors affecting the time at which heifers reach puberty and begin to cycle2,3.
Having some idea of CMW well in advance helps you manage nutrition and growth to achieve high pregnancy rates2,3.

How to determine the best time for joining

Heifers can occasionally join as young as 5 months of age, resulting in a calf at foot when the heifer is 15 months old.
This is undesirable and can especially lead to complications with calving.
The most important factor is not the age of the heifer, but the weight at joining4.


Heifers usually begin cycling at around 52% of mature body weight. Join them at approximately 66% of their mature body weight3.

MLA Recommendations for Heifers Reaching CMW5

Guide to minimum weights (kg) of weaner heifers at puberty6.

Frame score Weight at puberty Mating weight at 15 months Weight at 0-3 months pregnancy Weight at 4-6 months pregnancy Calving weight at 24 months Mature weight
1 240 260 296 319 333 400
2 270 300 342 369 387 470
3 290 330 377 409 430 530
4 310 365 419 454 487 600
5 340 400 459 499 525 670


Weigh heifers every 6 weeks after weaning to achieve growth targets for joining.

Action Points: MLA Recommendations for Heifers reaching CMW5

Manage parasites and diseases

Reproductive diseases and/or any other health issues that slow weight gain or cause weight loss will result in lower reproductive rates and significant economic loss7.
Poor worm control can reduce cattle growth rates by at least 20%8.

Practice good parasite management at weaning:
  • use a treatment that will be effective against the worm species in your area
  • drench again 3–4 weeks prior to joining (depending on seasonal conditions, locality and production system)
Manage external livestock introductions to minimise the risk of disease7.

Critical Mating Weights


Vaccinate breeding herds against infectious reproductive diseases, such as Pestivirus, Vibriosis and Leptospirosis8.

Utilize genetic tools and EBV’s*

When selecting bulls for your herd, select bulls with EBV’s associated with reproductive performance - Days-to-Calving, Scrotal size and Calving ease of daughters.
Extremes of rib fat resulting in very lean carcasses may also be associated with low reproductive performance in some instances.
Use selection indexes to balance selection for reproductive traits with selection for growth and performance.


Consider EBVs for reproductive traits as well as growth and performance when selecting bulls for your herd 

*EBV – Estimated breeding value – an estimate of an animal’s value as a parent for a particular production trait such as growth rate.

Achieve CMW to ensure Optimal Condition Scores at Joining

Heifers that have met CMW should achieve 85% pregnancy rates with a 6-week joining period.
Failure to achieve CMW may result in >15% empty females and difficulty achieving critical condition scores3,5.
Too low (<2.0) or too high (5.0) a condition score may result in calving problems10.

Minimum Condition Scores at Joining11*

Spring calvers Autumn calvers
Heifer: 3.0 (60-65% mature weight) Heifer: 3.0-3.5 (60% mature weight)
Cow: 3.0 Cow: 3.0
Bull: 3.5 Bull: 3.5
*Expect an average condition score to be at least 0.5 higher

Key Points to Achieve Critical Mating Weight

  • CMW: the weight at the start of the joining period at which 85% or more heifers will fall pregnant in a 42-day joining period3.   


Achieving CMW can increase herd profitability, productivity and longevity1–3.

CMW – What are the Recommendations


Key Products: Dectomax®

Delivers persistent activity to protect cattle against the most prevalent worm types
Has the most uniform days of persistent activity across worm types
Also controls key external parasites

Thank you

Zoetis Australia would like to thank and acknowledge the contribution and review of content provided by the ReptoActive Steering committee.

Dr John Wedd Ware

Senior Consultant, Mackinnon Project, Faculity of Veterinary Science, University of Melbourne, VIC

Dr Rod Manning

Davilak Pastoral Co, cattle consultant for M.S & A, Mansfield, VIC

Mr Mark Lucas

Consulting Agronomist, Rural Business Consultant, Pasture Agronomy Service, Tumut, NSW

Dr Bill Graham BVSc.

Beef Cattle Consultant, Coolac Veterinary Services Coolac, NSW

Mr Bill Hoffman

Managing Director, Hoffman Beef Consulting Pty Ltd, Tregeagle, NSW

Dr David Frith BVSc. MVSt.

Director of Quirindl Veterinary Group, Quirindl, NSW


For further information please refer to the following Tech Note:


Tech Note

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1. Schatz T. Heifer management in northern beef herds. 2nd Edition 2012. Meat and Livestock Australia.

2. Hamlyn-Hill F & Fordyce G. Heifer Management. Future Beef, 2012. Available from Accessed October 2013.

3. McConochie J. Selecting and managing beef heifers. New South Wales, Department of Primary Industries, 2007. Primefact #626.

4. Barber S. Successfully joining cattle. Published in Weekly Times 2011. Available from Accessed October 2013.

5. More Beef from Pastures. Procedure 1: Maximise the number of live calves per female. 2013. Meat and Livestock Australia.

6. More Beef from Pastures. Minimum liveweights of weaner heifers. 2013. Meat and Livestock Australia.

7. Reproductive diseases. 2012. Meat and Livestock Australia.

8. More Beef from Pastures. Choose the appropriate management practice, corrective treatment or a combination to prevent common diseases or disorders. 2013. Meat and Livestock Australia

EBV – Estimated breeding value – an estimate of an animal’s value as a parent for a particular production trait such as growth rate.

9.  Pitchford W. Selection and Management of the Maiden Heifer. 2012. Cooperative Research Council for Beef Genetic Technologies.

10. Shaw S-E. Heifer days a hit. 2009. Department of Agriculture and Food. 

11. More Beef from Pastures. Module 6: Weaner throughput. 2013. Meat and Livestock Australia.

Further Reading

A Better Way To Buy