Three sigmoidal growth equations were tested for their usefulness in fitting mammalian growth curves. The von Bertalanffy, Gompertz, and logistic equations were fitted to growth data by nonlinear regression techniques. The residual sum of squares and deviations of predicted neonate, weaning, and adult masses from observed values were used as criteria to choose among the models. The von Bertalanffy equation provided the smallest residual sum of squares, while the Gompertz equation fitted equally well by this criterion. The logistic equation overestimated neonate mass and underestimated adult mass, the Gompertz overestimated neonate mass, and the von Bertalanffy overestimated weaning mass. The Gompertz model was chosen to fit a sample of 331 species; growth rate constants, K , for these species are presented. The relationship of K to adult mass was calculated and was found to have a slope similar to that of altricial birds. K -values were found to be comparable to those reported by Case (1978) and consistently higher than those of Millar (1977). Species having differing rates from those reported by Case or Millar were also identified; ground squirrels had faster growth rates and seals had slower growth rates when rate of growth was estimated by the Gompertz equation.

Fitting Sigmoidal Equations to Mammalian Growth Curves

High-fat feeding during pregnancy and lactation affects offspring metabolism in rats

An animal's nutritional status depends on (1) nutrient accessibility, (2) nutrient demand, and (3) physiological, metabolic, morphological, and behavioral compensations that avert or minimize discrepancies, if any, between the first two. The main thesis of this essay is that the diversity and potency of such compensatory mechanisms have often been underrated, and hence the frequency and intensity of nutritional stress in free-living animals have often been exaggerated. This theme is explored in conjunction with an inventory of the modes of compensation for actual or potential dietary deficiencies.

Periods of Nutritional Stress in the Annual Cycles of Endotherms: Fact or Fiction?

Most of the residents of Heliconia, Colombia, live in a continual state of malnutrition characterized by a lack of protein and an excess of carbohydrate in the diet. Kwashiorkor and Marasmus are frequently observed when such dietary imbalances occur. These conditions are seen in Heliconia, but even when the recognized symptoms of clinical malnutrition are absent, there are long-term morphological changes associated with protein deficiency.



In the present study, interest is centered on the relative effects of protein deficiency on the skeletal maturation of apparently healthy boys and girls. Incidental comparisons of clinically-diagnosed Kwashiorkor and Marasmus patients with each other and with non-affected controls are also made. It is seen that skeletal maturation in early life is delayed in almost all Heliconia children when compared to U.S. standards. Female controls appear to experience a form of catch-up growth beginning in the preadolescent period, while male controls appear more severely retarded throughout adolescence. The result is a reduction in stature most pronounced in boys and a concomitant reduction in sexual dimorphism for overall body size. The Kwashiorkor- and Marasmus-affected children show a more severe retardation of skeletal growth with no significant sex difference in their response.

Nutritional stress and growth: sex difference in adaptive response.

Heat production of fasting white-tailed deer (Odocoilus virginianus) was measured over all months of the year. The deer were maintained in outdoor enclosures, they voluntarily restricted their feed intake and activity in winter, and experienced weight changes typical of wild deer. FMR followed a cyclic pattern. Average FMR of adults in summer coat from May through August (52.2 kcal/kg/24 hrs) was 1.5 times as high as that of deer in winter coat from September through April (33.8 kcal/kg/ 24 hrs). Results confirm the previously reported finding of lower metabolism in winter, and are in gen- eral conformance with reported changes in weight of thyroid glands, and certain activities of deer in an area of similar latitude in New York State. Date of measurement apparently had a stronger influence on FMR than either body size or sex. Values obtained were variable, and high compared to the accepted interspecies mean of 70 kcal/kg W?'7/24 hrs. Cyclic changes in metabolism in deer subject to normal weather conditions may represent a response to season and/or weather, and, in combination with other physiological and behavioral changes, form part of a complex adaptation for survival of deer living near the northern extremity of their range. Additional studies for determining total energy requirements are suggested. Abstract: Heat production of fasting white-tailed deer (Odocoilus virginianus) was measured over all months of the year. The deer were maintained in outdoor enclosures, they voluntarily restricted their feed intake and activity in winter, and experienced weight changes typical of wild deer. FMR followed a cyclic pattern. Average FMR of adults in summer coat from May through August (52.2 kcal/kg/24 hrs) was 1.5 times as high as that of deer in winter coat from September through April (33.8 kcal/kg/ 24 hrs). Results confirm the previously reported finding of lower metabolism in winter, and are in gen- eral conformance with reported changes in weight of thyroid glands, and certain activities of deer in an area of similar latitude in New York State. Date of measurement apparently had a stronger influence on FMR than either body size or sex. Values obtained were variable, and high compared to the accepted interspecies mean of 70 kcal/kg W?'7/24 hrs. Cyclic changes in metabolism in deer subject to normal weather conditions may represent a response to season and/or weather, and, in combination with other physiological and behavioral changes, form part of a complex adaptation for survival of deer living near the northern extremity of their range. Additional studies for determining total energy requirements are suggested.

C. E. French

Papers

Nutrient requirements for growth and antler development in the white-tailed deer'

Appraisal of nutrition in Haiti.

Responses of White-Tailed Bucks to Added Artificial Light

The influence of dietary fat and carbohydrate on growth and longevity in rats.

The Effect of High Versus Low Protein Equicaloric Diets on the Heat Production of Human Subjects