Abstract
The main purpose of this experiment was to assess species-specific growth patterns of spotbill ducks, Anas poecilorhyncha zonorhyncha Swinhoe, kept in captivity for breeding source.
Ninety-six eggs in 10 nests of the wild ducks were collected at Research Farm of Akita Prefectural College of Agriculture located Hachirogata reclaimed land, Akita, Japan, during laying and nesting season in 1976. Ducklings hatched from these eggs in incubators at the laboratory were weighed at hatch and weekly under conventional feeding and management in chicks and domestic ducks. The growth data from 15 male and 9 female youngs which survived to 20 weeks of age were fitted for each of Gompertz and Logistic curves.
Following equations were induced on the means of Gompertz and Logistic, respectively.
Gompertz, male: y=966.86×0.01490.6920t
female: y=837.07×0.02190.7081t
Logistic, male: y=954.53/(1+56.89e-0.5996t)
female: y=824.62/(1+49.90e-0.5729t)
where, y is body weight in grams and t is age in weeks.
The same results were obtained from the male and female ducks and summarized as follows.
1. In Gompertz the inflexion point tI corresponded with observed maximum growth period while in Logistic the case was not so.
2. The estimated weights from Gompertz equation approximated more closely to the observed ones during the first half growth period.
3. Coefficient of determination R2 was higher in Gompertz than Logistic.
From the above results, it would be concluded that Gompertz curves explained better than Logistic ones, about the growth patterns of the spotbill ducks for both male and female.
