Table 1.
Summary of the experimental manipulations for constraint‐MA (A) and cost‐MA (B). Note that some studies provided data for more than one experimental manipulation
| Experimental manipulation | Details | Sample size: studies (effect sizes) |
|---|---|---|
| (A) | ||
| Supplementation with antioxidants | For example, carotenoids, vitamins, synthetic compounds that led to a reduction in OS (i.e., decreased damage and/or greater antioxidant levels), compared with the unsupplemented group | 24 (63) |
| Supplementation with natural compounds | Compounds with potential antioxidant properties (e.g., prebiotics, probiotics, herbs, plant extracts) that led to a reduction in OS (i.e., decreased damage and/or greater antioxidant levels), compared with the unsupplemented group | 23 (63) |
| Exposure to stressors | Environmental stressors that induced OS (i.e., increased damage and/or reduced antioxidants), for example, inclusion of oxidized lipids in the diet, exposure to hypoxia, high stocking density, heat stress, toxins | 21 (58) |
| (B) | ||
| Nonea | Correlational studies in which the growth difference between groups was natural and statistically significant | 4 (18) |
| Compensatory growth | Food restriction followed by a period of ad libitum food, leading to compensatory growth in the experimental group | 7 (34) |
| Brood manipulation | Altering the number of chicks or hatching synchrony within a brood in avian studies. This led to increased growth in reduced broods compared with controls. Enlarged broods had decreased growth rates compared with controls, as did chicks that hatched asynchronously compared with synchronously. For one study, compensatory growth occurred later in life after an initial growth decrease of enlarged broods | 4 (8) |
| Dietary changes | Changes to protein and lipid composition of the diet. This included diets of differing quality with greater growth rates in high‐quality diet groups, as well as comparisons of different types of dietary proteins (e.g., fish meal, maggot meal, or soybean meal) and lipids (e.g., cod liver oil or vegetable oil) that had different effects on growth | 13 (60) |
a
None included comparisons between younger and older individuals with different growth rates, initially small late‐hatched and larger early‐hatched individuals and between individuals living at different elevations.