Free availability of high-energy foods led to energy over-ingestion and protein under-ingestion in choice-fed broilers

The objective of this study was to compare energy and protein content of the diet selected by choice-fed broilers with thatof broilers fed a balanced diet. One hundred and eighty 1-day-old male broilers were randomly assigned in groups of 10to one of three experimental treatments (n = 6). Control broilers were fed a standard balanced diet, whereas choice-fedbroilers were fed three foods which were more concentrated (Choice C+ treatment) or less concentrated (Choice C?treatment) in protein, carbohydrate or fat. We evaluated food intake behavior, nutrient intake, and performance param-eters of broilers from 2 to 7 weeks of age. Choice C+ broilers showed enhanced preference for the high-fat food, whichled to higher energy intake and lower protein intake than those of control broilers at 2 to 4 weeks of age. Body weight,weight gain and feed conversion efficiency were negatively affected by diet selection of Choice C+ broilers. Choice C?broilers selected a balanced diet, and showed performance parameters similar to those of control broilers. Our results supported the hypothesis that free availability of high-energy foods bias ingestive behavior of choice-fed broilers toward selecting a diet with higher energy and lower protein than needed for normal growth.Fil: Catanese, Francisco Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Rodríguez Ganduglia, Héctor. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Villalba, Juan Jose. State University Of Utah; Estados UnidosFil: Distel, Roberto Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina. Universidad Nacional del Sur. Departamento de Agronomía; Argentin

The expression of dietary conservatism in solitary and shoaling 3-spined sticklebacks Gasterosteus aculeatus

Dietary conservatism (DC) is a long-term, active avoidance of novel food by foragers, present in some (but not all) members of each forager population. Conservative prey choice by predators may exert strong selection pressure on prey populations because individuals with a novel appearance may be protected from predation by their novelty. Recent work has provided the first evidence of DC in a fish species, where novel-colored morphs of prey (Daphnia) were under predation by individual 3-spined sticklebacks Gasterosteus aculeatus. However, in this earlier study, sticklebacks were housed individually, whereas in the wild, they are a strongly shoaling species. Little is known about whether the social context may influence the expression of DC, but even if it does not, shoals are very likely to contain at least one nonconservative individual. Thus, most foraging shoals are expected to exert stronger selection against novel prey than are individual foragers. We found that DC, strong enough to drive a novel prey morph from initial rarity to fixation in a prey population, was evident among both single sticklebacks and shoals, but surprisingly, we found no evidence that isolated fish and shoals differed in the frequency with which they caused this to happen