Abstract
Ducklings of Spotbill Ducks that this report treated were incubated from eggs collected out of the wild nests, and were being raised with the commercial chick feed for 25 weeks (the experimental raising period) at Akita Prefectural College of Agriculture in 1976. Body weight of them was Weighed at hatch and every week. Using above data, twelve sets of three figures of average body weight are prepared, which arbitrarily selected from the initial, middle and final period of the experimental raising period (as an example, 0 week of age <at hatch> for the initial period : 6 for the middle period : 17 for the final period, etc). The Growth pattern of body weight for spotbill ducks is made clear by applying to the three points method of the Richards' Growth Curve Model. The fitness regarding every equation estimated from previous procedure is determined by the determination coefficient (R^2 value). (1) The growth pattern in spotbill ducks' ducklings shows high and rapid growing during the initial raising period. The age of week at the inflection point is 4.36 for male, and 3.76 for female, respectively, and both figures approximate to ones in ducks ("Peking" breed from Mainland China). (2) The shape parameter m shown the highest determination coefficient R^2 is 1.1 (R^2=99.74) for male at the age combination 1 : 8 : 19 among the twelve sets, and 0.8 (R^2=99.40) for female at 1 : 9 : 20, respectively. Therefore, the growth pattern in spotbill ducks for male approaches to the Gompertz curve, and for female, seems to be a transitional pattern from the Gompertz curve. (3) The relationship between the shape parameter m and the determination coefficient (R^2) shows one specific curve for male and female respectively, as well as ones of ducks and chickens.
