How do you measure fertility in beef herds?
Breeder performance is a key profit driver in beef businesses. To improve performance, we must measure it so we can assess and monitor it on an ongoing basis. Fertility calculations are completed by the 12 to 18-month period from joining to branding and weaning. It is the 2022-2023 joining that produces the calves you brand in 2024. So, what should be recorded to measure fertility?
Pregnancy rate
The first fertility assessment to undertake is pregnancy rate.
If 505 cows are joined in the 2022-23 mating (Table 1) and 435 were pregnant at the June 2023 pregnancy test, the pregnancy percentage calculation is:
Pregnancy % = (435/505) x 100 = 86.1%
If maiden heifers and first-calf cows are run together or with older cows, it is important to record their pregnancy test data separately. These animals are the most likely to have conception problems and having data on them enables identification of problems.
Branding and weaning rates
Branding and weaning rates should be calculated off total cows joined, less any pregnant cows sold before calving. For 2024-branded calves, the branding and weaning rates are calculated using the cows joined in the 2022-23 joining.
505 cows joined in 2022-23
435 cows pregnant in June 2023
402 calves branded January 2024
394 calves weaned June 2024
Branding and weaning percentage calculations are:
Branding % = (402/505) x 100 = 79.6%
Weaning % = (394/505) x 100 = 78.0%
Foetal and calf losses
Foetal and calf losses are calculated using the number of pregnant cows retained at the previous year’s pregnancy test. Pregnant cows that are sold before calving are not included in the calculations as they did not have the opportunity to produce a calf.
Following the 2022-23 joining of 505 cows, 435 were pregnant at the June 2023 pregnancy test. If these were all retained to calve the foetal and calf loss calculations are:
Foetal and calf loss: pregnancy test to branding = 435 – 402 = 33
Foetal and calf loss: pregnancy test to branding % = 33/435 x 100 = 7.6%
Calf loss: branding to weaning = 402 – 394 = 8
Calf loss: branding to weaning % = 8/402 x 100 = 2.0%
Foetal and calf loss: pregnancy test to weaning = 435 – 394 = 41
Foetal and calf loss: pregnancy test to weaning % = 41/435 x 100 = 9.4%
| Mating | 2021 - 2022 | 2022-2023 | 2023 - 2024 | |
|---|---|---|---|---|
| Calf year | 2022 | 2023 | 2024 | |
| Mating Period | 15/12/21 - 31/12/22 | 15/12/22 - 31/12/23 | 15/12/23 - 31/12/24 | |
| Calendar year | 2022 | 2023 | 2024 | |
| A | Cows joined | 500 | 505 | 505 |
| Pregnancy test | June 2021 | June 2022 | June 2023 | |
| B | PTIC cows | 430 | 435 | 435 |
| C | Pregnancy % = B/A x 100 | 86.0 | 86.1 | 86.1 |
| D | Pregnancy cows retained | 430 | 435 | 435 |
| Branding | ||||
| E | Calves branded | 400 | 402 | 402 |
| F | Branding % = E/Year before A x 100 | 80.8 | 80.4 | 79.6 |
| G | Foetal & calf loss - Pregnancy test to Branding = Year before D - E | 25 | 28 | 33 |
| H | Foetal & calf loss - Pregnancy test to Branding % = G/Year before D x 100 | 5.9 | 6.5 | 7.6 |
| Weaning | ||||
| I | Calves weaned | 394 | 394 | 394 |
| J | Weaning % = I/Year before A x 100 | 79.6 | 78.8 | 78.0 |
| K | Calf loss - Branding to Weaning = E - I | 6 | 8 | 8 |
| L | Calf loss - Branding to Weaning % = K/E x 100 | 1.5 | 2.0 | 2.0 |
| M | Foetal & calf loss - Pregnancy test to Weaning = Year before D - I | 31 | 36 | 41 |
| N | Foetal & calf loss - Pregnancy test to Weaning % = M/Year before D x 100 | 7 | 8.4 | 9.4 |
Year-round mated herds
Assessing fertility in year-round mated herds is more difficult. It is usually impossible to calculate branding or weaning percentages based on cows mated because with calves being branded and weaned and cows culled at each muster, it is difficult to identify the number of cows mated to produce the calves. One of the many advantages of controlled mating is it enables better assessment of herd performance.
Many producers with year-round mated herds calculate branding and weaning percentages based on the cows present at the second round in the previous year. This approach provides consistency but will not provide true branding and weaning percentages as cows will have been sold. In year-round mated herds where pregnancy testing is undertaken and the number of retained pregnant cows is known, foetal and calf loss from pregnancy testing to branding and or weaning can be determined.
Conception patterns
It is important to record foetal age and body condition scores when pregnancy testing. The conception pattern and body condition score data can help identify if fertility diseases or poor body condition may have affected the conception rate. Both vibriosis and trichomoniasis can cause embryonic failure and early abortions and are a common cause of low conception rates and delayed conceptions.
Foetal ageing provides the opportunity to identify superior cows who conceive early in the joining, and cull less fertile cows that are slow to conceive.