Table 3. LMM of the influence of parental age on offspring growth.
| Term | d.f. | Effect | s.e. | Wald stat (χ2) | P value |
|---|---|---|---|---|---|
| Chick mass | 1 | 1.286 | 0.0241 | 2844.66 | <0.001 |
| Day | 1 | −0.7757 | 0.005035 | 352.00 | <0.001 |
| Day2 | 1 | 0.003950 | 0.000036212 | 192.58 | <0.001 |
| Day3 | 1 | −0.000004450 | 0.0000006178 | 51.86 | <0.001 |
| Chick age | 1 | 1060 | 82.3 | — | — |
| Chick age2 | 1 | −699.8 | 50.5 | — | — |
| Chick age3 | 1 | 163.1 | 9.19 | — | — |
| Maternal age | 1 | 110.8 | 10.34 | — | — |
| Maternal age2 | 1 | −7.386 | 0.7003 | — | — |
| Paternal age | 1 | 113.4 | 9.27 | — | — |
| Paternal age2 | 1 | −7.503 | 0.6323 | — | — |
| Maternal age × Chick age | 1 | −122.3 | 17.33 | 49.83 | <0.001 |
| Maternal age2 × Chick age | 1 | −5.332 | 0.7114 | 49.50 | <0.001 |
| Maternal age × Chick age2 | 1 | 78.89 | 10.514 | 56.31 | <0.001 |
| Maternal age2 × Chick age2 | 1 | −5.332 | 0.7114 | 56.18 | <0.001 |
| Maternal age × Chick age3 | 1 | −17.42 | 1.899 | 84.14 | <0.001 |
| Maternal age2 × Chick age3 | 1 | 1.177 | 0.1286 | 83.69 | <0.001 |
| Paternal age × Chick age | 1 | −156.3 | 15.06 | 107.72 | <0.001 |
| Paternal age2 × Chick age | 1 | 10.46 | 1.021 | 104.96 | <0.001 |
| Paternal age × Chick age2 | 1 | 101.9 | 9.38 | 117.89 | <0.001 |
| Paternal age2 × Chick age2 | 1 | −6.807 | 0.6370 | 114.22 | <0.001 |
| Paternal age × Chick age3 | 1 | −22.72 | 1.723 | 173.92 | <0.001 |
| Paternal age2 × Chick age3 | 1 | 1.503 | 0.1170 | 164.99 | <0.001 |
d.f., degree of freedom; LMM, Linear Mixed Model; s.e., standard error.
The aim of the analysis was to examine the potential influence of parental aging on the early growth of their offspring. Repeated measurements of chick growth within the first month were used as the response variable and a LMM was implemented; constant=−813.6. In total, the analysis includes 493,700 measurements of 31,404 chick's masses belonging to 2,330 females and fertilized by a total of 1,074 different males. Note that chick identity was controlled in this model as a random effect, in addition to parental identity and year of breeding, to account for the use of repeated measures of chick mass within the analysis. Parental and chick age were loge transformed to improve model fit.
Numbers in superscript indicate that the terms have been fitted as a second/third order polynomial.