A variable growth rate modification of von Bertalanffy's equation for aquaculture

In aquaculture experiments of only a few months'duration, fish can approach their asymptotic size and growth rates may change greatly. One objective of aquaculture is to obtain a maximum economic return, and a growth model is needed to relate rate of growth to food consumption and other costs to find the optimum duration of growth cycles. Von Bertalanffy's equation is an asymptotic growth model which can be used for this purpose. A variable growth rate model was developed to describe fish growth oscillations observed in aquaculture experiments. This growth model provides improved estimates of von Bertalanffy's equation in aquaculture and can be used for an efficient evaluation of fish production during production cycles.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73180/1/j.1365-2109.1994.tb00689.x.pd

Typology of rainfall fields to improve rainfall estimation in the Sahel by the area threshold method

The stratification of rainfall fields to improve specific rainfall models is a subject that has received relatively little attention in the literature. It is shown here that objective classification techniques, based on the intensities and spatial distribution of the rainfall fields, can produce meaningful results in terms of the area threshold method (ATM) model and climatology. Four approaches for rainfall classification, using rain gauge data, are proposed in order to improve the average areal rainfall estimation in the Sahel by the ATM model. Two of them are based on the structural behavior of the rainy area (area where it rains above a given threshold) function against a threshold. Based on this function, a new parameter, called the under profile area (UPA), has been proposed for the classification of rainfall fields. The groups obtained from the method based on this parameter are characterized by different average spatial structures. A significant improvement on the ATM model is observed by considering classification based on the UPA parameter. An average reduction of 34 % of the root-mean-square error is observed in a validation term. This improvement is a direct consequence of the fact that the optimal thresholds are different from one group to another, which is an important point when considering the impact of classification on the ATM model. (Résumé d'auteur

Chemical composition, palatability and physical characteristics of venison from farmed deer

The quality of venison from farmed deer were evaluated based on chemical composition, palatability scores, W-B shear force, ultimate pH, and color. The samples of venison were derived from javan rusa (Cervus timorensis russa), moluccan rusa (Cervus timorensis moluccensis), sambar (Cervus unicolor brookei), fallow (Dama dama) and imported red deer (Cervus elaphus). Moluccan rusa and red deer were fed grass. Javan rusa, sambar and fallow deer were fed concentrate. The venison obtained from grazing deer (grass-fed) gave higher moisture content (75.3%) than concentrate-fed or confinement-raised deer (74.4%) and imported venison (70.62%). Fat content in venison shows some differences between muscles and species. The concentrate-fed animals had a higher (P 0.05) palatability scores than grass-fed venison. Feeding regimens (grass-fed vs. concentrate-fed) significantly (P < 0.05) influenced fat composition in the venison of farmed deer in this study