Fertility Traits: Why Recording Days to Calving and Scrotal Size Matters

Reproductive performance is the most important driver of profitability in a beef enterprise. While growth, carcase merit and market premiums all contribute to returns, none can compensate for poor fertility. A cow that misses a calf in a 12-month cycle reduces herd productivity, and a bull that sires’ daughters with poor reproductive performance slows generational progress. This is why accurate recording of fertility traits, particularly Days to Calving (DTC) and Scrotal Size (SS) is essential. Even in herds that already have good reproductive performance, it is important to monitor genetic trends for these traits.  

Why Days to Calving (DTC) Matters 

DTC EBVs estimate genetic differences in the interval from the start of joining to subsequent calving. Lower (more negative) values are favourable, indicating females more likely to: 

• Conceive earlier in the joining period 

• Re-calve sooner after calving 

• Maintain tighter calving patterns across their lifetime 

This trait captures the genetic component of female fertility, directly rewarding early calving females and penalising those that fail to calve. Because fertility is influenced by both genetics and management, DTC EBVs help separate the genetic signal from management noise. 

What Needs to Be Recorded 

Accurate EBVs depend on complete, consistent records. BREEDPLAN requires: 

• Joining details – all joining events for each female across the breeding season must be recorded. This includes every bull joined, with start and end dates, and any multiple sire joining. 

• Disposal information – dates and reasons for females removed between joining and calving.  It is important to note that BREEDPLAN uses specific DTC disposal codes to separate fertility culls from other reasons.   

• Calf details – every calf born, alive or dead, to avoid penalising females incorrectly. 

Heifer records are particularly important. Information on females that fail to calve is as valuable as those that succeed, as it reveals the true fertility distribution in a herd. Pregnancy test results are not yet utilised but can be submitted and are likely to have a greater role in future evaluations. 

A new fertility module is being developed, this will include the ability to utilise both AI records and natural matings. AGBU have been working to incorporate AI records into the analysis of female fertility, and we strongly encourage Hereford breeders to submit AI mating records as well as natural joining records, because this data is required to complete the development work. 

Why Scrotal Size Matters 

On the bull side, Scrotal Size EBVs are an indirect but powerful fertility measure. These EBVs are calculated from scrotal circumference measurements taken at around 400 days of age. Larger scrotal circumference is consistently associated with: 

• Earlier puberty in bulls 

• Higher semen production and improved semen quality 

• Earlier cycling and puberty in daughters 

For example, a bull with a Scrotal Size EBV of +4 cm would be expected to sire sons with larger testes and daughters that reach puberty earlier, compared with progeny from a bull with a -1 cm EBV. This demonstrates that scrotal circumference measurement is not only a descriptor of male reproductive development but also a practical genetic indicator of female fertility. 

How to Record Scrotal Circumference 

Scrotal circumference measurement is straightforward but must be consistent: 

• Pull testes to the bottom of the scrotum 

• Measure at the widest point with a tape 

• Apply light tension to leave a slight skin indentation 

• Record in cm to one decimal place 

• Bulls can be measured between 300–700 days of age.  Ideally measurements should be taken as the mob is going through puberty, often around 400 days. 

Only the first measurement per bull is analysed. Using self-tensioning devices such as Reliabull tapes reduces operator variation. 

The Commercial Value 

For commercial producers, fertility EBVs are not just stud-level measures. Bulls with favourable DTC and Scrotal Size EBVs: 

• Produce daughters more likely to join successfully as yearlings 

• Deliver earlier conceptions and shorter calving intervals 

• Lift weaning percentages and kilograms of beef per hectare 

This creates more reliable breeding herds and stronger financial performance. Importantly, EBVs complement, not replace, management. Nutrition, animal health and joining strategies remain essential, but without genetic progress, producers are limited by inherent fertility constraints. 

Take-Home Message 

Among the many EBVs available, fertility traits are sometimes undervalued because their impact is less immediately visible than growth or carcase traits. Yet fertility underpins all other production. Without a calf, no other trait adds value.  Recording DTC and Scrotal Size is straightforward, but the impact is far-reaching. These heritable traits allow breeders to make faster, more reliable gains in reproductive performance. For Hereford breeders, prioritising DTC and Scrotal Size EBVs strengthens maternal reputation and ensures clients receive cattle that conceive earlier, calve regularly and maintain productivity year after year.