EARLY NUTRITION AND PHENOTYPIC
DEVELOPMENT: ‘CATCH-UP’ GROWTH LEADS TO
ELEVATED METABOLIC RATE IN ADULTHOOD
François Criscuolo*, Pat Monaghan*, Lubna Nasir† and Neil B. Metcalfe*‡
* Ornithology Group, Division of Environmental and Evolutionary Biology,
Institute of Biomedical and Life Sciences, Graham Kerr Building, University of
Glasgow, Glasgow G12 8QQ, UK; and †Veterinary Pathological Sciences,
University of Glasgow, 464 Bearsden Road, Glasgow G61 1QH, UK
Online supplementary materials
Husbandry conditions
Adult zebra finches from our stock population were paired randomly in breeding
cages (60x45x40 cm) with an external nesting box, in a room maintained at 20-22 ºC
and relative humidity of 45-55% under full spectrum artificial light (16:8, L:D cycle).
Prior to their eggs hatching, parent birds were kept on a diet comprising mixed seeds
(foreign finch mixture, J.E. Haith Ltd, UK) including some soaked overnight seed to
saturation, grit, cuttlefish and water ad libitum. They also received 5g of conditioning
food (13.6% protein) per breeding pair daily (a mixture of conditioning food (J.E.
Haith Ltd, UK)) and fresh spinach, Daily Essentials vitamin supplement (The
Birdcare Company, UK) and Calcivet calcium supplement once a week (Vetafarm,
Australia). Cages were checked daily and records made of dates of egg laying and
hatching. Zebra finch chicks fledge from the nest at around 20 days of age in our
population and self-feeding begins around 30 days.
On hatching of the first egg, broods were allocated to either the high or the
low quality diet. The high quality rearing diet was the same as the pre-hatching parent
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diet plus 5g of homogenized hard-boiled hens’ egg per family daily, whereas the low
quality diet comprised only mixed seeds (including some soaked overnight to
saturation) and water ad libitum, weekly fresh spinach, calcium supplement, and
vitamin supplement in the water once a week.
After the offspring were removed at 30d, the parent birds were separated and
rested for 2 weeks. In order to generate enough offspring, almost all (29 out of 31) of
the pairs were then induced to breed a second time but were allocated to a different
rearing diet treatment.
Juvenile mortality measured at fledging was low (between 10 and 14 %), and
did not differ among treatment groups (F3,168.8 = 0.25, p = 0.86).
Measurement of metabolic rate
Oxygen consumption was measured using Sable Systems International (USA)
apparatus where an external air supply was distributed by a respirometer manifold
MF-8 to five metabolic chambers (1800 cm3), placed in a temperature-controlled
cabinet. The air was dried over drierite before entering the respirometer manifold, and
then again over drierite and ascarite (for CO2 trapping) when leaving the metabolic
chambers. Air flow through the chambers sub-sampled by a TR-RM8 respirometer
multiplexer was regulated by a calibrated mass flow controller and mass flow control
valve (MFC-2, Sable System). This system allowed us to direct air from each
respirometry chamber in turn to an oxygen analyzer (Sable System FC-1B) for
measurement, while simultaneously flushing air through the other chambers. The flow
rate of air entering both measured and unmeasured boxes was set to 490 ml min-1 in
all trials. At the beginning of each trial, the oxygen analyzer was calibrated using dry
outside air (set to 20.95% oxygen). Data were collected and analyzed using Datacan
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acquisition software (Sable System). Rates of oxygen consumption were calculated
using formula 4b of Withers (1977).
The actual mean ages at which respirometry was conducted were 14.15 ± 1.09
d, 30.51 ± 2.22 d, 212.41 ± 32.17 d; there was no differences in age at measurement
with respect to diet treatment (p>0.50). To ensure that the measurement was not
influenced by short term responses to diet, all measurements at 15 d were prior to the
diet switch and at 30 d prior to the transfer of all groups to the common diet. All
measurements were conducted at 35 ºC, which is within the thermoneutral zone of the
zebra finch (Rønning et al. 2005); they correspond to resting metabolic rates, defined
as rates of oxygen consumption measured in quiescent animals in a postabsorptive
state. We chose to measure RMR rather than BMR due to logistical problems in
measuring metabolic rates at night in such a large number of birds (182 individuals
measured on three separate occasions), and to ensure compatibility with previous
studies (Selman et al. 2001; Verhulst et al. 2006). Individual RMR was measured two
(n=13 birds) or three times (n=2) on separate days at the same approximate age to
check for the repeatability of our method of metabolic measurement. Repeatability (r
calculated following Lessells & Boag (1987)) was high at 0.70 (F13, 154.9 = 2.569, p =
0.042).
Growth rates of experimental birds
The skeletal and feather growth response to the dietary treatments was similar as
when measured in terms of body mass. Thus birds from the H diet group had larger
tarsus and wing lengths at day 15 (14.84 ± 0.06 vs. 14.66 ± 0.06 mm, F1,183.8 = 15.00,
p < 0.001; 44.36 ± 0.34 vs. 42.96 ± 0.34 mm, F1,183.9 = 5.38, p = 0.021, respectively).
As with body mass, growth in wing length from day 15-30 differed among the 4 diet
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treatments, the LL group showing the highest, and the HH group the lowest wing
growth (14.98 ± 0.27 (LL), 13.64 ± 0.24 (LH), 13.51 ± 0.26 (HL), 13.16 ± 0.25mm
(HH), F3,168.3 = 9.01, p < 0.001). There was no difference in tarsus growth among diet
treatments at this stage (F3,170.0 = 0.23, p = 0.87), due to birds having almost reached
their adult tarsus length by 15 days.
Reference List
Lessells, C. M. & Boag, P. T. 1987 Unrepeatable repeatabilities: a common mistake.
Auk 104, 116-121.
Rønning, B., Moe, B. & Bech, C. 2005 Long-term repeatability makes basal
metabolic rate a likely heritable trait in the zebra finch Taeniopygia guttata. J.
exp. Biol. 208, 4663-4669.
Selman, C., Lumsden, S., Bunger, L., Hill, W. G. & Speakman, J. R. 2001 Resting
metabolic rate and morphology in mice (Mus musculus) selected for high and
low food intake. J. exp. Biol. 204, 777-784.
Verhulst, S., Holveck, M. J. & Riebel, K. 2006 Long-term effects of manipulated
natal brood size on metabolic rate in zebra finches. Biol. Letts. 2, 478-480.
Withers, P. C. 1977 Measurement of VO2, VCO2 and evaporative water loss with a
flow-through mask. J. Appl. Physiol. 42, 120-123.
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