On the optimal growth of the alimentary tract in avian postembryonic development

Abstract

It was shown in the mathematical model described elsewhere that when growth rate of the chicks is maximized and not constrained by the food availability, the optimal relationship between body mass and alimentary tract mass should conform to a single straight line, or two‐, or three‐segmented straight lines. Here, we present the data on growth of 11 bird species, and we test the model using the mass of intestines as an indicator of growth of the alimentary tract. The results support the predictions of the model for altricial species and contradict them for precocials. Since precocial species examined here were not food‐limited, we suggest that the lack of optimal growth of their alimentary tract is inherent to their mode of development. This may account for their lower growth rate, as compared to altricials. The existence of the optimal growth of the alimentary tract in altricial nestlings suggests that under natural conditions the food is much more abundant than it is generally assumed.

Seasonal variation in growth of greater snow goose goslings: the role of food supply

“…However, most studies in birds have shown that ospring of birds that breed the earliest grow and survive best (Perrins 1970;Daan et al 1988;Sedinger and Flint 1991;Cooch et al 1991a; but see van Noordwijk et al 1995). A ®rst explanation of this paradox could be that growth in birds is relatively insensitive to natural variation in food supply (Konarzewski et al 1989(Konarzewski et al , 1990. However, there is experimental evidence that protein and energy intakes during the nestling period aect growth rate and ®nal adult size (Johnson 1971;Jùrgensen and Blix 1985;Boag 1987;Lindholm et al 1994).…”

“…Thus, there is controversy about how much variability in growth rate can be explained by variation in food. Some authors have argued that growth rate is largely constrained by physiological factors rather than by food availability (Ricklefs 1983;Konarzewski et al 1989Konarzewski et al , 1990. However, most of these studies were on altricial birds which are fed by their parents with protein-rich food such as insects.…”

Energy assimilation, parental care and the evolution of endothermy

“…An increased growth rate contributes again to decreased mortality of the young. When food available to the young is not a limiting factor, it is optimal to allocate as much energy as possible to the organs related to energy assimilation at the early stage of the growth (Konarzewski et al 1990). Thus, a maximum growth rate is possible when the young minimize investments into locomotor activity.…”

Reproductive maturity of turkey hens: egg composition, embryonic growth and hatchling transition

“…Intestinal development has been the subject of recent reviews (Moran, 1985;Dibner et al, 1996;Sell, 1996;Noy and Sklan, 1997;and Uni, 1999). Functional maturation of the small intestine is both a physical and physiological process and is one of the main constraints to early growth after hatching (Konarzewski et al, 1989(Konarzewski et al, , 1990Ricklefs et al, 1998). Physiological maturation (in terms of digestive and absorptive functionality) of the digestive tract involves the increased production of pancreatic and intestinal enzymes (Nitsan et al, 1991a,b;Sell et al, 1991;Pinchasov and Noy, 1994) and changes in nutrient transporters (Holdsworth and Hastings-Wilson;1967;Shehata et al, 1984;Obst and Diamond, 1992).…”