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| Independent variable | Coefficient | Significance level |
| Birth year | 3.9 | P <.00001 |
| Cycle year | –8.9 | P <.00001 |
| Married (or not) | –41.9 | P <.00001 |
| Body weight (kg.) | –5.6 | P <.00001 |
| Ranch Hand (vs. Control) | 4.2 | P = 0.620 |
