The quantity-quality trade-off: differential effects of daily food times on reproductive performance and offspring quality in diurnal zebra finches

Abstract

An abundant food supply is crucial to reproductive performance, as shown by restricted food availability experiments, in small-sized vertebrates including birds. However, whether daily feeding times affect reproduction is largely unknown. The present study investigated the effects of daily food availability times on reproductive performance and quality of eggs and offspring survivors in zebra finches (Taeniopygia guttata). In randomly paired birds kept under a 12 h:12 h light:dark cycle for about 52 weeks, food availability period was restricted to 4 h in the morning [morning food availability (FA) group] or evening (evening FA group), with controls provided with food ad libitum; thus, the daily food deprivation period began after 4 h of food availability in the morning food access group and was continuous with night-time starvation in the evening food access group. Both food restrictions adversely affected reproductive health, as shown by reduced sex steroid and mesotocin levels, but not general metabolism, as indicated by the absence of a difference in thyroxin and triiodothyronine levels. Restricting food access to a 4 h period negatively affected reproductive performance, although there were differences between pairs in the morning and evening FA groups. In particular, there was delayed onset of reproduction and compromised reproductive success in evening FA but not in morning FA pairs; conversely, offspring health was severely compromised in morning FA but not in evening FA group pairs. Furthermore, morning FA group females were in better health, implying a sex bias in parental food provisioning. Overall, we demonstrate trade-off of 'quantity' (number of offspring produced and/or survived) for 'quality' (how healthy offspring were) in response to daily food availability times in zebra finches, which, much like humans, are diurnal and retain the ability to reproduce throughout the year.

Changes in brain peptides associated with reproduction and energy homeostasis: Putative roles of gonadotrophin‐releasing hormone‐II and tyrosine hydroxylase in determining reproductive performance in response to daily food availability times in diurnal zebra finches

“…This is consistent with evidence indicating that food deprivation increased hypothalamic deiodinases in the arcuate nucleus, and leptin administration reversed this effect in mice . Nevertheless, imposed feeding regimes in the present study led to significant differences in the reproductive performance of zebra finches despite the fact that (i) ad lib. and evening‐only groups experienced a similar 12‐hour ‘no‐feeding’ period (ad lib.…”

“…Birds were housed in light‐tight boxes (size: 42 × 30 × 54 cm) lit by compact florescent lamps (5 W, 220‐240 V; CFL lamps; Philips, Eindhoven, The Netherlands) and providing a 12L:12D (L = ~200 lux, D = 0 lux) light regime. The experimental protocol has been described in detail previously . Briefly, birds were acclimated to cage conditions and kept in same‐sex groups (n = 4 per cage) with food available ad lib.…”

“…After 1 week of reduced food availability period in the same‐sex cage, males and females from identical food conditions were taken out and paired; thus, we formed 12 pairs (one pair per cage) in each feeding regime: ad lib., morning‐only and evening‐only. Pairs were allowed to live with the same partner for approximately 12 months to determine food‐time‐induced effects on reproductive health and reproductive fecundity . Thereafter, breeding pairs were separated, re‐housed in same‐sex groups and maintained on lighting and feeding regimes, as before, for the next 8 weeks to minimise the influence of co‐habitation on food‐induced effects on neuroendocrine pathways.…”

“…In the face of the reported absence of seasonal or food‐induced differences in GnRH‐I and GnIH expression in previous zebra finch studies, we predicted that, as related to effects on reproductive output, feeding conditions would affect the GnRH‐II and TH expression because they play roles in the transduction of social cues and sexual behaviour . We also anticipated sex differences in the expression pattern of candidate molecules because the neuroendocrine response and reproductive strategies could differ between male and female birds …”

“…To a diurnal species that forages for most, if not all, of the day, food availability for a short period could affect reproductive performance, and the effect could vary depending on whether the food deprivation period was before or after the food availability period during the day. Indeed, a recent study demonstrated that, compared with food available ad lib., zebra finch pairs having access to food for 4 hours in the morning maintained reproductive fecundity but produced poor quality offspring (as indicated by body mass and skeletal growth), whereas those having access to food for 4 hours in the evening produced fewer but better quality offspring over a study period of about 12 months . However, it is not known whether the long‐term daily nutrition deficit affected the hypothalamic peptide and enzymatic regulatory pathways involved in reproductive regulation.…”