1. Scrotal Circumference in Bulls: Should We Adjust for Age or Weight?
Janice M. Rumph
Montana State University

2. Scrotal Circumference
Producers often select for increased scrotal circumference
Decreased age at puberty
Increased fertility
Currently adjusted to a yearling basis

3. Justification
Some concern about the correct way to present scrotal circumference
Age adjusted (365-day)
Weight adjusted

4. AICA Data
Bulls had to have yearling weight and scrotal circumference measured on the same day
7,410 bulls
26,117 animals in pedigree

5. Heritabilities & EPD Values
Sire EPD Range
σ2p
Age
0.39 (0.04)
-2.1 to +2.8
6.28cm2
Weight
0.38 (0.04)
-2.0 to +2.4
5.42cm2
Adjustment

6. r = 0.90
Age Endpoint
Weight Endpoint

7. What does this mean?
Adjusting for an age endpoint results in virtually no difference than a weight endpoint
Does that mean age is the most appropriate endpoint?
Not necessarily

8. Scrotal Circumference in Bulls: Should We Adjust for Age or Weight?
Janice M. Rumph
Montana State University