Skip to main content
ARS Home » Research » Publications at this Location » Publication #73366
Title: MODELING TURKEY GROWTH WITH THE RELATIVE GROWTH RATE.

Author
item Maruyama, Kimiaki - Kim
item POTTS, WILLIAM - UNIVERSITY OF MARYLAND
item BACON, W - OHIO STATE UNIVERSITY
item NESTOR, K - OHIO STATE UNIVERSITY

Submitted to: Growth Development and Aging
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Whether we are selecting birds for breeding or feeding them for marketing, it is an advantage to be able to predict body weight at a given age and also to be able to estimate the genetic potential and physiological characteristics of growth with a minimum number of days. Six conventional sigmoidal growth curves were fitted to body-weight data to distinguish growth patterns of fast growing and control lines of turkeys. The sigmoidal functions produced acceptable growth curves with some reasonable degrees of goodness of fit to the body-weight data. However, when growth curves were derived from the relative growth rate in two discrete growth phases, considerably better goodness of fit was obtained. With new growth curves, it was possible to distinguish the growth characteristics of two lines of turkeys as early as 60 days, instead of 100 days, when a conventional selection took place.

Technical Abstract: Sigmoidal growth curves were fitted to body-weights of male and female turkeys from two genetic lines; a fast-growing (F) line and a randombred control (RBC) line from which the F line was developed. The logistic, Gompertz, von Bertalanffy, Richards, Weibull, and Morgan-Mercer-Flodin curves all demonstrated systematic lack of fit. The primary source of the lack of fit was identified with nonparametric estimates of the relative growth rate (the growth rate as a fraction of the body weight). The above sigmoidal curves could not accommodate features of the estimated relative growth rate. Based on the feature of the relative growth rate, two new growth curves were derived from a segmented two-phase model. decreases in two linear phases with slopes of B1 and B2 joined together at time=K, gave growth curves that fit the experimental data acceptably. The linear-linear model with the smooth transition rendered better fit over the model with the abrupt transition. When the growth curves of male and female turkeys were compared, B1, B2, and K were smaller in males. When the F line was compared to the RBC line, B1 and K were smaller and B2 was closer to zero, indicating that the relative growth rate declined rapidly until about 61 days of age in the F line, while it declined less rapidly until about 71 days of age in the RBC line.