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The effect of sex on the pattern of fat deposition in mice selected for body conformation: agonistic selection
Ricardo J. Di Masso; Patricia S. Silva; Maria Teresa Font
Departamento de Ciencias Fisiológicas, Facultad de Ciencias Médicas, Universidad Nacional de Rosario, 2000 Rosario, República Argentina
ABSTRACT
Patterns of fat deposition were investigated in male and female mice divergently selected for body conformation. Selection was carried out with an agonistic criterion between body weight and tail length, in contrast to antagonistic selection previously performed. Within-sex patterns of fat deposition were compared between lines with the logarithmic form of the allometric equation.
Although selected lines were significantly different in body weight, no difference in adult fat content was found between them. Females of both selected lines showed a non-weight-dependent pattern of fat deposition, as found with antagonistic selection, while males showed a weight dependent pattern for both selection procedures.
Selected females did not differ in mature body fat content whether they were selected for high or low body weight, though in both cases they were fatter than unselected controls. These results are explained in terms of adaptive behaviour related to fitness. A critical degree of fatness would be necessary in females to allow the start of the reproductive cycle.
In contrast, no such response was evident in selected males. They did not differ from controls in adult fat percentage. When selection for body size was performed following the natural correlation between body weight and tail length, selected individuals would be heavier because of being bigger and not fatter. This would permit more effective exploitation of the source of genetic variance for body weight associated with appetite, avoiding that associated with energy partitioning.
Body conformation, as herein described, could be an important trait in selection programs directed to obtain lean animals in livestock production, particularly in pigs.
Keywords: Sex; Fat deposition; Mice; Agonistic selection.
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