Modeling the growth of laboratory and farm animals: Part 1. Monotocus animals and the relationship of birth weight, gestation time, and mature size

This article presents an analysis comparing the point of birth on the growth curves of three monotocus species (cattle, horses, and sheep). The growth curves of individual animals were normalized using mature size of the animal and gestation length, and a birth ratio was established using the length of gestation divided by the fraction of maturity at birth (F _b). The value of the birth ratio was found to be very similar for all three breeds, indicating that the fraction of maturity at birth is an important factor in determination of the length of gestation. A relationship was developed predicting F _b as a function of gestation time, and a procedure was developed to predict an animal's mature weight using birth weight and gestation time. Examples are shown indicating the efficacy of the predictions compared to the values of mature size found from the growth curve regressions.