Table 8.
Age as a predictor of testosterone. Individual, age range of analysis, age variable (age, age category), effect size with standard error (SE), Wald statistic, and p-value from GLMMs; and relative effect of age on mean testosterone concentrations. Degrees of freedom (df) is 1 in all pair-wise comparisons.
| Individual | Age Range of Analysis | Age Variable | Effect Size (SE) | Wald | p | Age Effect |
|---|---|---|---|---|---|---|
| Male1 | ~34–43 | Age (years) | −0.066 (0.021) | 9.681 | 0.002 | Decreasing |
| 31–40 (reference) a | ||||||
| 41–50 | −0.097 (0.125) | 0.606 | 0.436 | - | ||
| Male2 | 32–53 | Age (years) | −0.027 (0.004) | 37.043 | <0.001 | Decreasing |
| 31–40 (reference) a | ||||||
| 41–50 | −0.289 (0.056) | 26.262 | <0.001 | Lower | ||
| 51–60 | −0.432 (0.088) | 23.858 | <0.001 | Lower | ||
| Male3 | ~34–44 | Age (years) | −0.090 (0.015) | 38.079 | <0.001 | Decreasing |
| 31–40 (reference) a | ||||||
| 41–50 | −0.495 (0.082) | 36.783 | <0.001 | Lower | ||
| Male4 b | 15–32 | Age (years) | −0.017 (0.005) | 10.509 | 0.001 | Decreasing |
| 11–20 (reference) a | ||||||
| 21–30 | −0.081 (0.063) | 1.655 | 0.198 | - | ||
| 31–40 | 0.167 (0.128) | 1.697 | 0.193 | - |
a Reference category for GLMMs against which other age categories are compared. b Age analysis includes only mature bulls, which started at age 15 for this individual.