Table 2.

Estimates of variance components, heritability, and the genetic coefficient of variation on the standard deviation level (${\text{GCV}}_{\text{SDe}}$)

Estimate	TNB	LnVarTNB	varTNB
Permanent sow variance	0.86 (0.01)	–	0.15 (0.003)
Additive genetic variance	1.33 (0.2)	0.033 (0.001)	0.037 (0.002)
Residual variance	7.67 (0.8)	1.33 (0.4)	0.84
Heritability	0.135 (0.02)	0.024 (0.002)a	0.036a
${\mathrm{GCV}}_{\mathrm{SDe}}$b	–	0.091	0.096

TNB: litter size as total number born

LnVarTNB: phenotypic variability of litter size estimated by the log-transformed variance of residuals

varTNB: phenotypic variability estimated with double hierarchical generalized linear model measured in 121,088 sows from the Large White pig population

^aHeritability is a measure of the reliability of EBV for LnVarTNB and varTNB; it does not reflect the magnitude of the genetic variance in varTNB

^bMeasure of the genetic variation in residual variance ${\mathrm{GCV}}_{\mathrm{SDe}}=\frac{{\mathrm{\sigma }}_{\mathrm{a}ddv}\left({\mathrm{\sigma }}_{\mathrm{e}}\right)}{\overline{{\mathrm{\sigma }}_{\mathrm{e}}}}\approx \frac{1}{2}{\mathrm{\sigma }}_{\mathrm{avar}}\text{or}\approx \frac{1}{2}{\mathrm{\sigma }}_{\mathrm{av}}$