Why weigh calves?
Weighing suckler calves at weaning can help analyse how the cows have performed during lactation, and perhaps inform culling decisions.
Weighing suckler calves post weaning, and at regular intervals during the growing period, can be used to identify where weaning or management (feeding, ration formulation etc.) over winter has had an impact on growth rates – be that positive or negative. Changes can then be made to reverse any downward trends or to target practices that have led to improved growth, resulting in improved herd performance.
Fundamentally, it is not possible to identify even significant dips in growth rates by eye – in order to monitor and to make changes we must first measure – get weighing!!
How often should I weigh and how many?
Gold standard would be to weigh every animal monthly post weaning. As a minimum, I would recommend weighing all suckler calves at weaning and then aim to weigh at least a proportion, several times between weaning and turnout. If weighing only a proportion of the group, be sure to select a representative sample.
What data do you want?
Essential information: –
- Calf ID
- Calf sex and breed
- Calf birth date
- Weaning date
- Weight, and date weighed
“Nice to have” extra data :-
- Calf birth weight (don’t worry if you don’t have this – it can be estimated)
- Dam ID (this allows us to analyse dam lactation performance)
How do I record weight data?
Some clients can use their management software to input calf weight data – this can then be forwarded to your vet as an Excel spreadsheet by Whatsapp or email. I have helped others who have paper records to get basic information onto a simple spreadsheet. This can be used in future for inputting weight data.
What do I calculate?
*If birthweight is unknown, you can use an average of 40kg; however, breeds vary so try and use an estimate adjusted for your herd.
Identifying initial trends:
Calf ID numbers increase across the bottom (i.e. animals to the right are younger). This data reveals post-weaning growth rates of earlier calves outperforming those of later-born calves in 2021.
The herd compacted the calving period to minimise age spread at weaning and cut the number of late born calves. Additional advice has been given to improve management of any later born calves post-weaning. The 2022 graph demonstrates the improvements.
Counting the cost:-
Early- and late-born calves achieved similar growth rates pre-weaning (the blue trend line is flat). It was post-weaning where the impact of being born later became apparent.
|Commercial herd||Early born calves||Later born calves|
|Average 200 day weight (weaning)||216Kg||216Kg|
|Average DLWG birth-200d||1Kg/day||1Kg/day|
|Kg to gain over growing period||300Kg||300Kg|
|Av. DLWG post-weaning growing period||0.95Kg/day||0.7Kg/day|
|Time taken to reach target weight to move to finishing group (516Kg) from weaning||315 days||428 days|
|Age to start finishing||515 days (17 months)||628 days (21 months)|
|Estimated finishing DLWG (assume similar difference in DLWG continues but rates up on finishing ration)||1.2Kg/day||0.9Kg/day|
|Weight gain required during finishing||110Kg||110 Kg|
|Time taken to achieve finishing weight (target 626Kg)||92 days (3 months)||122 days (4.1 months)|
|Age at slaughter||607 days (20.2 months)||750 days (25 months)|
|Approximate feed conversion efficiency (Kg DM / Kg LW)||12||16|
Approximate feed conversion efficiency in Table 1 shows that it takes 4 Kg DM (dry matter) more feed to add 1 Kg of LW (live weight) to the later born calf at finishing.
- Lower feed conversion efficiency means higher lifetime feed costs
- And you have to keep them for 5 months longer to achieve the same finishing weight: longer on farm means higher bedding, feed and labour costs, increased risk of death or disease and increased vet costs!
The faster animals grow, the more profitable they are, whether you are selling weaned calves or stores or finishing your own youngstock.
The key factors for maximising growth in this herd were:-
- Small age range in the calves through good cow fertility and tight calving pattern.
- Careful management of later born animals.
A final thought:-
Knowledge is power! If you know where growth is suboptimal, you can start to work out why and make improvements, thus maximising your herd productivity an
Written By Louise Silk