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Modellierung des Ernährungsstatus bei der präasymptotischen und relativen Wachstumsrate in einer heterogenen Hühnerpopulation
Author(s) -
Aggrey Samuel E.
Publication year - 2004
Publication title -
journal of animal breeding and genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.689
H-Index - 51
eISSN - 1439-0388
pISSN - 0931-2668
DOI - 10.1111/j.1439-0388.2004.00462.x
Subject(s) - gompertz function , biology , linear growth , population , growth rate , body weight , zoology , linear regression , endocrinology , mathematics , demography , statistics , geometry , sociology
Summary This study was undertaken to use the spline linear regression to model pre‐asymptotic body weight measurements from an unselected random‐bred chicken population fed two different protein diets. The spline linear regression model is a compound function comprising of series of linear models. It was used to compartmentalize growth into segments. The birds raised under the low‐protein diet had four compartments, whereas those raised under the high‐protein diet had three compartments. Whereas the protein level defined the number of splines or compartments, the growth potential demonstrated by the sexes were different. The males under low‐protein diet grew faster than the females under high‐protein diet. Even though both sexes responded to high‐protein diet, a high‐protein diet in females was not enough to raise their growth potential to that of males under low protein levels. The efficiency of growth under the two protein levels were assessed with relative growth. Relative growth rate is the increase in body weight per unit of body weight per unit of time, and it represents the efficiency of an animal as a producer of new body mass material. The maximum relative growth modeled by the Gompertz function for both sexes under the two protein levels were observed at day 6 and hereafter, declined proportionally to a proponent of the amount of growth remaining. Despite the high absolute growth of the birds fed a high‐protein diet compared with their counterparts fed a low‐protein diet, the relative growth rates of the two groups were comparable. Modelling both absolute and relative growth show that the maximum absolute and relative growth rates occur within different time frame, as a result, selecting on absolute growth rate for improved relative growth within the same time frame or vice versa may not achieve the desired selection goal. The use of the spline regression and relative growth models would have practical application for commercial broilers and broiler breeders where growth is either truncated before the asymptote or controlled by dietary and other environmental factors to prevent excessive obesity.