Tc. Bridges et al., Relativity of growth in laboratory and farm animals: I. Representation of physiological age and the growth rate time constant, T ASAE, 43(6), 2000, pp. 1803-1810
This article presents a modification of the growth function of Bridges et a
l. (1986) that incorporates a known biological time unit (gestation period)
to represent physiological time for a given animal species. Gestation time
was incorporated into the weight-age equation and modified by the growth r
are rime constant, c, which relates the inflection point of the growth curv
e to a relatively fixed time unit. Relating the inflection point of the gro
wth curve to an animal's gestation period provides a mathematical basis for
changing growth curves to account for the "external" influences of managem
ent, diet, environment and health that may impact an animal's growth in app
roaching mature size. Examples are shown using the developed mathematical e
xpression to predict changes in the growth of two different cattle under th
e effects of early weaning and different nutritional and environmental cond
itions.