Food restriction delays breeding and affects insulin‐like growth factor‐1, oxidative damage and haematocrit value before egg‐laying in female canaries

Abstract

Environmental challenges, such as fluctuations in food availability, could influence reproductive investment. If resource availability is poor, individuals need to decide in which life‐history process they invest more energy and vital compounds, which determine the cost of reproduction. In resource allocation, the physiological pathways have important roles. The aim of our study was to examine whether food availability influenced physiological traits (insulin‐like growth factor‐1 (IGF‐1) concentration, antioxidant capacity (OXY), level of oxidative damage (ROM) and haematocrit value) prior to egg‐laying in female canaries Serinus canaria. We also tested whether these physiological traits were associated with traits reflecting the reproductive investment in egg macro‐ (egg mass and yolk mass) and micronutrient content (eggshell biliverdin‐ and protoporphyrin‐based colouration). To test these questions we conducted a food restriction experiment with control and food‐restricted (72% of control food) groups. Our study showed that food‐restricted canary females delayed egg‐laying and the physiological traits differed between the groups. At the pre‐laying period, after 9–11 days of treatment, a reduction in plasma IGF‐1 concentration, ROM level and haematocrit value was detected in the control group, whereas in the food‐restricted group plasma IGF‐1 concentration increased, while ROM level and haematocrit value did not change. Plasma level of OXY was not influenced by treatment or breeding period. Plasma concentration of IGF‐1, haematocrit value and oxidative status before egg laying did not affect the egg characteristics. Our study highlights the importance of breeding stage when studying and interpreting the effects of food restriction on physiological traits of breeding birds. Moreover, our data suggest that nutritional limitation had an effect on the timing of egg‐laying that could be mediated by changes in physiological variables.

Food Restriction Reveals Individual Differences in Insulin-Like Growth Factor-1 Reaction Norms

“…However, another study on broiler chicken found that food restriction resulted in higher IGF-1 levels than controls throughout the study (from 15 to 28 weeks of age) (Hocking et al, 2007). We also found that female canaries responded to food restriction by increasing IGF-1 levels during breeding (Hargitai et al, 2022). These studies only analyzed the overall response to food-restriction, but here we show that within a single population, individuals may differ markedly in their physiological response to changes in nutritional conditions.…”

Sex‐specific effects of dietary restriction on physiological variables in Japanese quails

“…It has been also reported that IGF1 increases the expression of genes involved in steroidogenesis in avian preovulatory follicles, which improves egg production (Francoeur et al., 2023). Contrarily, DR during the pre‐laying period increased circulating IGF‐1 levels in domesticated canaries, but did not have a significant effect on egg quality traits (Hargitai et al., 2022).…”

“…Additionally, the physiological response to dietary restriction may vary among avian species. For instance, we previously found that DR decreased liver IGF1 gene expression in male and female Japanese quails ( Coturnix japonica ) (Reda, Ndunguru, Csernus, Knop, Lugata, et al., 2024), whereas other studies have reported that DR increased plasma IGF‐1 in female canaries ( Serinus canaria ) (Hargitai et al., 2022), broiler chicken hens (Hocking et al., 1994) and male and female bearded reedlings ( Panurus biarmicus ) (Tóth et al., 2022). These mixed results indicate that, based on the existing evidence, it is difficult to draw a general conclusion about how changes in food availability affect the IGF‐1 system.…”