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Strain differences in whole‐body protein turnover in the chicken embryo a

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T. Muramatsu , K. Hiramoto & J. Okumura

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Laboratory of Animal Nutrition, School of Agriculture, Nagoya University, Chikusa‐ku, Nagoya, 464–01, Japan Published online: 08 Nov 2007.

To cite this article: T. Muramatsu , K. Hiramoto & J. Okumura (1990) Strain differences in whole‐body protein turnover in the chicken embryo, British Poultry Science, 31:1, 91-99, DOI: 10.1080/00071669008417234 To link to this article: http://dx.doi.org/10.1080/00071669008417234

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British Poultry Science (1990) 31: 91-99

STRAIN DIFFERENCES IN WHOLE-BODY PROTEIN TURNOVER IN THE CHICKEN EMBRYO T. MURAMATSU, K. HIRAMOTO AND J. OKUMURA

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Laboratory of Animal Nutrition, School of Agriculture, Nagoya University, Chikusa-ku, Nagoya 464-01, Japan Received for publication 28th July 1989

Abstract 1. Whether or not there is a strain difference in embryonic whole-body protein turnover rates was tested using the chicken embryos of Rhode Island Red carrying a sex-linked dwarf gene (dwarf), White Leghorn (layer), and White Cornish x White Plymouth Rock (broiler) strains on day 12 of incubation. 2. Whole-body protein synthesis was estimated by injecting L-[ 1 5 N]phenylalanine either intraperitoneally or intravenously on day 12 of incubation in order to investigate the effect of the route of isotope administration. The results showed that the values for fractional and absolute synthesis rates were approximately 13% higher by intravenous injection than by intraperitoneal injection. 3. Whole-body protein turnover, both in terms of fractional and absolute rates, was significantly faster in dwarf than in broiler embryos, with intermediate values in layer embryos, although no growth differences were observed on day 12. 4. Difference in egg weight, measured before incubation, did not affect protein turnover. 5. It was concluded that the strain difference manifested in wholebody protein turnover of the chicken embryo would probably be a reflection of differences in genetic background.

INTRODUCTION

Al-Murrani (1978) reported that embryonic growth was one of the determinants of post embryonic growth of chickens. This led the present authors to question whether the growth and protein turnover rates of embryos from birds of various strains already differ during incubation. Because the embryonic, as well as post embryonic, growth rate is more or less controlled by genes and their expression, the difference in the growth of various strains of chickens may probably already occur during the incubation period. The fact that the weight of unincubated eggs affected late embryonic 91

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growth and chick growth (Al-Murrani, 1978; Shanawany, 1987) may be in favour of the possible strain differences in embryonic growth. It follows, therefore, that if there were differences in embryonic growth between various strains, either increased protein synthesis or decreased protein degradation, or both, is likely to be responsible because the predominant portion of embryonic growth is accounted for by protein accretion. Marked changes in protein turnover rates in the whole chicken embryo were found during the incubation period when rapid accretion of body protein is taking place (Muramatsu et al., 1987a). The present study was conducted to investigate whether or not there is a strain difference in whole-body protein turnover between chicken embryos. MATERIALS AND METHODS

Experiment 1

Fertilised eggs from Rhode Island Red, having a sex-linked dwarf gene (male dw/dw, female dw/-; Dwarf strain), single comb White Leghorn (layer strain) and broiler (White Cornish X White Plymouth Rock; broiler strain) hens were obtained from Gifu Poultry Experimental Station (Gifu, Japan) and incubated for 14 d at 38°C and about 70% relative humidity. On day 12 of incubation, 12 or 15 eggs were taken and the embryos were injected with L[15N]phenylalanine intraperitoneally. About half the embryos were taken for the measurement of the isotope enrichment at 10 and 60 min. after the injection. The details of the method of measuring whole-body protein synthesis were described previously (Muramatsu et al., 1987a). On day 10 and 14, 3 or 4 embryos were also taken for the measurement of embryo weight and protein content to determine the net protein accretion rate, thereby deriving protein degradation rate from the difference between synthesis and accretion rates. Protein and RNA contents were measured by the methods of Lowry et al. (1951) and of Munro and Fleck (1969), respectively. The enrichment of free and protein-bound [15N]phenylalanine was determined with a selected-ion quadrupole gas-chromatograph mass-spectrometer (QP-1000, Shimadzu Co. Ltd, Kyoto, Japan) after extraction of the amino acid. The calculation for fractional rate of protein synthesis was done as described previously (Muramatsu et al., 1987a). Experiment 2

The experiment was carried out to investigate the effects of the route of isotope administration, i.e. intraperitoneal injection, which was used in experiment 1, or intravenous injection, which was believed to be a better method, if it could be established. Fertilised eggs from single comb White Leghorn hens maintained in the Laboratory of Animal Nutrition, School of Agriculture, Nagoya University, were used and incubated for 12 d at 38°C with relative humidity of approximately 70%. On day 12 of incubation, 48 eggs were distributed into 2 groups,

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to which L-[ N]phenylalanine (31-1 atom% excess) was given either intravenously or intraperitoneally at a dose of 1 -22 mg in 0*1 ml of 0-85% (w/v) sodium chloride solution. The eggs were then returned to the incubator. At 10 or 60 min after the injection, half the eggs from each treatment were taken out, and the embryos were treated as in experiment 1. Intravenous injection was done in a clean room as follows. The eggs were placed on a tray, and a hole approximately 10 mm in diameter was made in the shell around the centre of the broad end near the air space with an electric drill, and the dust was removed with an electric vacuum cleaner. Egg shell membrane was removed carefully so that bleeding from veins running near the membrane did not occur. The largest vein that could be seen was gently pulled up using forceps with flattered tips, and the forceps fixed to a stand. A fine silk string was tied gently round the vein, and a 27 G needle inserted into the vein distal to the site tied with the silk string. After injection of the isotope, the string was tied firmly and the vein returned inside the egg. The hole in the shell was covered with tape, and the egg returned to the incubator until it was taken out again for analyses of the content of protein and nucleic acids, and wholebody protein synthesis. The entire procedure of intravenous injection was completed within several minutes, slightly longer than that for intraperitoneal injection. Experiment 3

Fertilised eggs from single comb White Leghorn hens maintained in our laboratory were incubated for 12 d in the incubator at 38°C and about 70% relative humidity as in experiment 1. Before incubation, the eggs were classified into two groups, viz. 10 eggs of small size (less than 55 g) and 20 eggs of large size (more than 58 g). The mean egg weights were 60-6 ±0-5 g (mean± SEM) for large size and 53*2 ±0-8 g (SEM) for small size, respectively. On day 12 of incubation, L-[15N]phenylalanine was administered and whole-body protein synthesis was determined as in experiment 1 except that the isotope was injected through a vein near the egg shell membrane as in experiment 2. After injection the vein was tied round with fine silk so that any leak of the isotope was prevented. Protein and RNA contents, and the enrichment of free and protein-bound [15N]phenylalanine were determined as in experiments 1 and 2. Statistical analysis

Analyses of variance were performed and the differences between means were assessed by a protected LSD method. RESULTS

Experiment 1

Table 1 shows egg weights and embryo weights after 10 to 14 days of incubation in the dwarf, layer and broiler strains used. The egg weight of the

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dwarf strain tended to be lighter than those of the other two strains, and significant differences were observed on day 12. On day 14 egg weight was significantly lower in dwarf than in layer strains. In contrast, no significant differences were found in embryo weights from the different strains until day 14 of incubation when the broiler embryos were heavier than those of the other two strains. TABLE 1

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Egg weight and embryo weight from dwarf,1 layer2 and broiler3 hens during incubation (experiment 1) Day of incubation Egg weight4 (g) 10 d 12 d 14 d Embryo weight (g) 10 d 12 d 14 d

Dwarf

Strain Layer

Broiler

52-5 (4) 54-4» (12) 52-6a (3)

61-2 (4) 59-4» (15) 64-0b (3)

58-8 (4) 62-0b(15) 57-l» (3)

Pooled SEM 2-5 1-1 1-9

2-17 (4) 5-03 (12) 9-94!'(3)

2-23 (4) 5-05 (15) 9-37* (3)

2-40 (4) 4-97 (15) 12-00b (3)

0-11 0-14 0-54

1 Obtained from Rhode Island Red having a sex-linked dwarf gene (male dw/dw, female dw/—) chickens. 2 Obtained from single comb White Leghorn chickens. 3 Obtained from White Cornish X White Plymouth Rock chickens. 4 Measured before the incubation. Values in parentheses are numbers of embryos used. Means not sharing a common superscript letter are significantly different at P

Strain differences in whole-body protein turnover in the chicken embryo.

1. Whether or not there is a strain difference in embryonic whole-body protein turnover rates was tested using the chicken embryos of Rhode Island Red...
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