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British Poultry Science Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/cbps20
Further investigations on protein requirement of genetically lean and fat chickens a
B. Leclercq & G. Guy
a
a
Station de Recherches Avicoles , I.N.R.A. , Nouzilly, 37380, France Published online: 08 Nov 2007.
To cite this article: B. Leclercq & G. Guy (1991) Further investigations on protein requirement of genetically lean and fat chickens, British Poultry Science, 32:4, 789-798, DOI: 10.1080/00071669108417404 To link to this article: http://dx.doi.org/10.1080/00071669108417404
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/ page/terms-and-conditions
British Poultry Science (1991) 32: 789-798
FURTHER INVESTIGATIONS ON PROTEIN REQUIREMENT OF GENETICALLY LEAN AND FAT CHICKENS B. LECLERCQ AND G. GUY Downloaded by [University of Illinois at Urbana-Champaign] at 21:08 15 March 2015
Station de Recherches Avicoles, I.N.R.A., 37380 Nouzilly, France Received for publication 17th November 1990
Abstract 1. Genetically lean (LL) or fat (FL) chickens were fed from 28 to 42 d of age on one of 6 diets with different protein contents (from 73 to 208 g/kg). In order to keep a constant amino acid balance the experimental diets were made by diluting a well-balanced proteinrich diet with a protein-free diet. 2. Dietary protein influenced the growth rate of both genotypes similarly. However, maximum weight gain was reached in LL at a lower protein intake than in FL. 3. Regression between total protein gain (body protein + feather protein) or body protein gain and protein intake exhibited significantly different slopes, that of LL being superior to that of FL. 4. At a given protein intake, feather protein gain was also superior in LL to FL. Moreover feather protein, as a percentage of total protein gain, was superior in LL to FL. When the dietary protein fell below 126 g/kg, feather protein represented a higher proportion of total protein gain. 5. Multiple linear regressions of protein intake (as the dependent variable), and body weight and protein gain or weight gain (as the independent variables) suggest that the maintenance requirement for protein is similar in both lines but that the protein efficiency for growth is significantly superior in LL. 6. In a second experiment both genotypes were offered either a single high protein diet (232 g/kg) or a single medium protein diet (186 g/kg) or had free-choice between a high (269 g/kg) and a low protein (145 g/kg) diet. In free-choice feeding, FL chickens selected an overall dietary protein content which was significantly lower (179 v. 200 g/kg) to that of LL. In both genotypes, free-choice feeding led to fatter and less efficient chickens than predicted by the linear regression between adiposity or food conversion and protein content. INTRODUCTION
Genetically lean and fat chickens from several experimental lines have been found to exhibit different protein gain to protein intake ratios, the lean 789
Downloaded by [University of Illinois at Urbana-Champaign] at 21:08 15 March 2015
790
B. LECLERCQAND G. GUY
genotype always having the better efficiency (Pym and Farrell, 1977; Leclercq, 1983; Whitehead and Griffin, 1984; Sorensen et al, 1983; Geraert et al, 1990). This was shown using frequently only one diet (Pym and Farrell, 1977; MacLeod et al, 1988; Sorensen et al, 1983; Whitehead and Griffin, 1984) and sometimes using several diets with different protein contents (Leclercq, 1983; Whitehead and Parks, 1988; Geraert et al, 1990). However, in this last situation, the protein content was modified by varying the respective proportions of cereal, soyabean meal and fat, so that amino acid profiles varied simultaneously. The present experiments were undertaken: (1) to compare diets with different protein contents but with similar amino acid profiles in order to be able to distinguish the difference in protein requirement for either maintenance or protein deposition; (2) to look for the ability of the fat and lean genotypes to adjust their protein consumption when they are offered two diets with different protein contents. MATERIALS
Birds came from fat and lean lines selected in our laboratory since 1976 (Leclercq, 1988); they belonged to the 10th generation. Only males were used in both experiments. Chicks all exhibited fast feathering. Experiment 1: Chickens were fed on a common starter diet from hatching to 28 d of age when the experimental period started. Birds (10 to 12 per treatment) were placed in individual cages in a temperature-controlled room (22°C constant). They were offered one of the 6 experimental diets made by mixing differing proportions of 2 basal diets, a protein-rich diet and a proteinfree diet, whose compositions are presented in Table 1. The 6 mixtures were calculated to contain 6 different crude protein concentrations, varying from 70 to 200 g/kg. The protein-rich diet contained some synthetic amino acids so that it had the 'ideal' profile according to the requirements suggested by Boorman and Burgess (1985). Diets were given ad libitum as pellets (2-5 mm diameter). At the beginning of the experimental period (28 d of age) 10 birds per genotype were killed to determine their body composition. The experimental period lasted 14 d (28 to 42 d of age). At the end of this period all chickens were killed by pentothal injection. All birds were plucked just after death. Feather weight was determined by weighing birds before and after plucking. Moreover, feather samples were kept to determine their dry matter and their protein contents. Plucked chickens were frozen until analysis. Body composition was determined after grinding each bird twice. Samples of ground material were freeze-dried. Lipid content was measured by ether extraction. Protein content was measured as nitrogen by a Kjeldahl procedure. Experiment 2: Chickens were given the same starter diet as in experiment 1 until 14 d of age. They were then placed in individual cages in a temperaturecontrolled room (22°C). Three treatments were compared from 14 to 49 d of age: a single high protein diet (232 g/kg), a single medium protein diet (186 g/kg), a free-choice between two diets differing in their protein contents (145
791
PROTEIN REQUIREMENT OF LEAN AND FAT CHICKENS TABLE 1 Composition of basal diets (g/kg)
Experiment 1
Downloaded by [University of Illinois at Urbana-Champaign] at 21:08 15 March 2015
Protein diet Maize Maize starch Straw Rapeseed oil Soyabean meal Soyabean protein Calcium carbonate Dicalcium phosphate Salt Trace minerals Vitamins DL-methionine L-lysine L-threonine L-histidine L-valine AMEn (calculated) (MJ/kg) Crude protein (measured)
400 120 40 250 130 10 20 4 1 5
4-55 2-30 1-00 0-33 0-29 13-08
Experiment 2
Energy diet
Low protein diet 860
820 99 40 105 10 20 4 1 5
10 15 5 1 5
13-08
259
0
12-75 145
High protein diet 542
20 250 150 10 15 5 1 5 3
12-79 269
TABLE 2 Crude protein content of experimental diets (g/kg), as determined
Experiment 1 Diet 1 Diet 2 Diet 3 Diet 4 Diet 5 Diet 6
73 102 126 152 180 208
Experiment 2 Single diet A Single diet B Free choice low protein diet high protein diet
186 232 145 269
or 269 g/kg). Food troughs were always in the same relative positions for the choice fed birds. All diets were fed as pellets (2*5 mm diameter). Broilers were weighed and slaughtered at the end of the experimental period. Abdominal fat was measured. Each treatment consisted of 14 chickens. Food consumptions were individually measured each week in the free-choice treatment and for the whole experimental period for the single diet treatments. The protein contents of the experimental diets are summarised in Table 2. Single diets were made by mixing appropriate proportions of the two diets used for the free-choice feeding treatment.
RESULTS
Live weight, body composition and food consumption of experimental groups are presented in Table 3. As the protein content increased from 73 to 180 g/kg> growth rate of both genotypes increased. No difference was ob-
792
B. LECLERCQAND G. GUY TABLE 3
Live weight (g), body composition (g) and food consumption (g) of lean and fat male chickens during the experimental period (experiment 1) Age (d) 28
Dietary protein Line LL
(gAg)
FL
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42
73
102
[
J
Ir
LL FL LL
J
FL
126
{ \
LL
J
FL
{ 152
f
LL
J
FL
180
1[
J
I 208
[
LL FL LL
J
FL
{ 1
Food consumption (28-42 d)
Live weight 459-3 (43-4)1 466-8 (40-8)
Feather protein 11-24 (1-06) 11-10 (0-97)
Body protein 75-11 (7-10) 73-74 (6-44)
702-5 (85-4) 719-7 (113-5)
20-74 (2-40) 18-72 (2-96)
93-45 (11-70) 93-39 (13-70)
139-4 (27-10) 176-0 (36-40)
1066 (182-4) 1177 (182-0)
744-6 (103-6) 767-9 (127-4)
24-02 (3-08) 20-86 (4-20)
110-54 (18-32) 104-57 (20-40)
104-1 (23-91) 157-4 (26-79)
1088 (160-1) 1160 (200-5)
851-8 (130-9) 869-7 (157-8)
26-41 (4-12) 23-12 (4-54)
128-40 (19-91) 123-10 (22-22)
110-0 (31-30) 169-9 (42-11)
1172 (163-0) 1252 (244-9)
998-1 (115-7) 964-9 (150-6)
32-39 (4-75) 27-43 (4-40)
150-45 (22-93) 135-70 (22-93)
118-9 (27-50) 170-2 (27-89)
1274 (135-3) 1306 (188-4)
1080-5 (111-2) 1069-5 (91-6)
35-30 (4-23) 31-78 (2-71)
166-21 (22-94) 152-40 (16-32)
120-6 (28-71) 182-2 (19-00)
1300 (146-4) 1441 (144-6)
1068-1 (119-4) 1067-0 (122-2)
36-73 (6-45) 33-64 (3-73)
165-80 (18-43) 157-10 (18-04)
100-7 (23-19) 169-8 (17-23)
1257 (116-2) 1383 (158-6)
Lipids 33-61 (3-15) 54-91 (4-82)
Standard deviation.
served between genotypes when weight gain was plotted against dietary protein content (data not shown). However, when weight gain was plotted against protein intake (g/kg live weight) the slope of the regression of the lean genotype (LL) was steeper than that of the fat genotype (FL) and the plateau was reached at a lower protein intake in LL than in FL (data not shown). Food consumption was influenced by the dietary protein content, increasing as protein increased and tending to plateau (or slightly decrease) beyond a dietary protein content of 152 g/kg. FL always exhibited a higher lipid content and lower body protein and feather protein contents than LL chickens. Changes in total protein gain (body protein + feather protein), body protein gain and feather protein gain as functions of protein intake are presented in Figs 1, 2 and 3, respectively. Regression coefficients of total protein gain v. protein
793
PROTEIN REQUIREMENT OF LEAN AND FAT CHICKENS lew
—
100c
g.
/'
80-
c
proi
5
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/
/ 60-
o
40-
/
/
n / •
/
i
\
100
200
300
Protein intake ( g )
FIG. 1.—Relationship between total protein gain and protein intake of FL (•) or LL (p) chickens between 28 and 42 d of age (experiment 1). lOO-i D--D
c
'5 6 0 c °a>
o
40-
T3 O
m 20-
I 100
\ 200
300
Protein intake ( g )
FIG. 2.—Relationship between body protein gain and protein intake of FL (•) or LL (•) chickens between 28 and 42 d of age (experiment 1).
intake were significantly different between FL and LL (F = 5-01), that of LL being higher than that of FL. The respective equations were: LL: total protein gain (g) = 0-5661 (±0-0272) protein intake (g) - 15-88 "r= 0-945 FL: total protein gain (g) = 0-4545 (±0-0231) protein intake (g) — 13-26 r= 0-943
794
B. LECLERCQ AND G. GUY OVJ —
20-
o Q.
Downloaded by [University of Illinois at Urbana-Champaign] at 21:08 15 March 2015
10-
s. 0-
•
i
100
•
i
200 Protein intake ( g )
300
FIG. 3.—Relationship between feather protein gain and protein intake of FL (•) or LL (n) chickens between 28 and 42 d of age (experiment 1).
Similarly different values were calculated for the coefficient of regression of body protein gain v. protein intake (F = 4-97). Regression equations were: LL: body protein gain (g) = 0-4678 (±0-0250) protein intake (g) - 17-02 r = 0-933 FL: body protein gain (g) = 0-3739 (±0-0203) protein intake (g) - 13-33 r = 0-936 Lastly regression lines of feather protein gain v. protein intake did not exhibit significantly different slopes (F = l-70). However, these lines were significantly distant (F = 46-6), LL always being superior to FL. Multiple linear regressions were calculated between protein intake (g/d) as the dependent variable and mean live weight (kg) and total protein gain (g) as the independent variables. Calculations were made excluding data from diet 6 (208 g protein/kg) because it led to a non-linear response. These equations were: LL: protein intake (g/d) = 6-04 (±0-85) live weight (kg) + 1-357 (±0-101) protein gain (g) R2 = 0-895 r.s.d. = 1-365 g/d FL: protein intake (g/d) = 6-07 (±0-98) live weight (kg) + 1-747 (±0-132) protein gain (g) R2 = 0-886 r.s.d. = 1 -658 g/d The coefficients of live weight were not different between genotypes, whereas the coefficient of protein gain was lower in LL than in FL. Similar equations were calculated using body protein instead of live weight. This led to similar conclusions, the coefficients of body protein (maintenance requirement) being similar in both genotypes. Lastly, equations were calculated using mean live weight and weight gain as independent variables. Treatments exhibiting the
795
PROTEIN REQUIREMENT OF LEAN AND FAT CHICKENS
wo — c
*-
2 a.
p \
0-5-
o
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\
-
s. 0-3c ID
s
\ \
~5 0-4-
\ n ~ * ———.
•—
•
0-2-
tt>
c •-
o 0-1 u
1
• 1 100 200 Protein intake (g)
•
300
FIG. 4.—Feather protein as proportion of total protein gain in FL (•) and LL (•) chickens according to protein intake (experiment 1).
TABLE 4
Growth performance between 24 and 49 d of age and abdominal fat proportion at 49 d of lean (LL) and fat (FL) male chickens given a high or low protein diet or choice between a high and a low protein diet (experiment 2)
Single diet B (232 g protein/kg) Live weight gain (g) Food conversion Live weight at 49 d of age (g) Abdominal fat/live weight Single diet A (186 g protein/kg) Live weight gain (g) Food conversion Live weight at 49 d of age (g) Abdominal fat/live weight Free choice (two diets) Live weight gain (g) Food conversion Live weight at 49 d of age (g) Abdominal fat/live weight Selected overall protein content (g/kg)
FL
LL
1066 (127) 2-09 (0-09) 1310 (177) 0-0253 (0-0048)
1185 (121) 1-88 (0-11) 1440 (148) 0-0050 (0-0020)
1067 (136) 2-16 (0-14) 1301 (179) 0-0341 (0-0085)
989 (99) 2-09 (0-09) 1243 (143) 0-0104 (0-0039)
1098 (140) 2-26 (0-10) 1325 (177) 0-0412 (0-0065) 176(31-5)
998(152) 2-16 (0-18) 1255 (172) 0-0112 (0-0048) 204 (39-5) < = 2-02
Analysis of variance (F value)
Weight gain Food conversion Live weight at 49 d Abdominal fat/live weight
Line effect (d.f.: 1,78) 0-50 22-5 0-0 426
Dietary effect (d.f.: 2,78) 4-38 24-0 3-05
Interaction (d.f.: 2,78) 6-00 2-47 3-17
29-3
5-70
Standard residual deviation 130-2 0-122 166-7 0-547
796
B. LECLERCQAND G. GUY
lowest and the highest protein content were excluded because they deviated from linearity. Equations were:
Downloaded by [University of Illinois at Urbana-Champaign] at 21:08 15 March 2015
LL: protein intake (g/d) = 4-49 (±1*19) live weight (kg) + 0-2805 (±0-0241) weight gain (g) i?2 = 0-907 r.s.d. = 1-12 g/d FL: protein intake (g/d) = 3-89 (±1-63) live weight (kg) + 0-3274 (±0-0327) weight gain (g) i? 2 -0-870 r.s.d. = 1-53 g/d The results from experiment 2 are given in Table 4. The weight gain of the FL was not modified by dietary treatment, whereas that of the LL was significantly lower on the low protein diet and on the free-choice diets. Overall, the dietary protein content of FL chickens offered the choice between a low and a high protein diet was significantly lower (179 g/kg) than for LL chicken (200 g/kg)- This difference occurred from the second week of the experimental period (172 v. 193 g/kg) and it was significant during the second and the fourth weeks (176 v. 204 g/kg). Lowering the dietary protein content induced an increase of fattening and of food conversion in both genotypes; however, these two parameters were higher for the free-choice diets than predicted by linear regressions calculated from single diets. Correlations between weekly selected overall dietary content of FL and LL chickens offered free-choice diets are given in Table 5. Correlations between selected dietary content during the first (21 to 28 d of age) and following weeks for the whole experimental period were very poor and not significant. Conversely, correlations between weekly selected dietary protein contents of the following weeks were very significant. TABLE 5
Correlations between weekly selected overall dietary protein content of fat (FL) and lean (LL) chicken offered a choice of low and high protein diets
2nd week 3rd week 4th week Total
1st week 0-318 0-079 0-002 0-302
2nd week
3rd week
4th week
0-591' 0-6611 0-8551
0-6931 0-8621
0-8661
1
Significant at the 001 level. Selected dietary protein content were 192 and 200 (1st week), 172 and 193 (2nd week), 179 and 201 (3rd week) and 176 and 204 g/kg (4th week) for FL and LL, respectively. DISCUSSION
The relative sensitivity of fat and lean chickens to dietary protein is controversial. Leclercq (1983) observed that the growth rate of chickens from the LL is significantly reduced when their dietary protein content fell below 191 g/kg, whereas that of FL is not modified between 152 and 211 g/kg. This observation confirmed previous work from Touchburn et al. (1981) using the same experimental lines. The results from the present experiment 2 lead to the
Downloaded by [University of Illinois at Urbana-Champaign] at 21:08 15 March 2015
PROTEIN REQUIREMENT OF LEAN AND FAT CHICKENS
797
same conclusion. However, Geraert et al. (1990), comparing these two lines, did not find different sensitivities to dietary protein. A similar observation has been made in the present experiment 1. Whitehead and Parks (1988) and Whitehead (1990) compared the growth rates of two experimental lines selected for low (lean line) or high (fat line) plasma VLDL (very low density lipoprotein) concentration as a function of dietary protein content. They did not observe a higher sensitivity of their lean genotype to low protein content. Discrepancies between all these observations might be caused by a specific requirement of the lean genotype for one or more amino acids, because aminoacid profiles were not kept constant in most of the experiments and because in the lean genotype feather protein represents a higher proportion of total protein gain than in the fat genotype. This may result in differing requirements for amino acids. LL chickens were found to be better users of dietary protein to make both feather and body (muscles and organs) protein at any given protein intake. This higher yield of LL is not the result of a lower maintenance requirement for protein because both genotypes exhibited similar maintenance requirements whatever the way of expressing this requirement. In contrast, the requirement for protein gain was always lower in LL than in FL. This led to a lower protein requirement per g of weight gain. The slope of the regression between protein gain and protein intake is significantly higher in LL than in FL confirming our previous observation (Leclercq, 1983). One explanation of this genetic control of protein utilisation could be different partitioning of amino acids, the fat chickens using more amino acid carbon to make fatty acids (Saunderson, 1988). The hormonal control of this different use of amino acids for proteinogenesis or lipogenesis needs to be investigated more precisely. LL chickens were also able to synthesise more feather protein than FL. This confirms a similar observation from Whitehead and Griffin (1985) in their own experimental lines. In our lines this cannot be explained by a difference in the fast-feathering gene because both genotypes were selected for fast-feathering (kk) from the F3 generation and because all chickens were controlled from hatching in the present experiment. We must conclude that both feather protein and body protein are synthesised in greater amounts in LL chickens. Moreover, the present experiment suggests (Fig. 4) that feather protein synthesis has priority over body protein synthesis when protein intake is reduced. This priority occurred in the present experiment when dietary protein content was lower than 126 g/kg (ideal protein). When offered a choice between a low and a high protein diet, FL chickens selected a mixture whose protein content was 20 g/kg lower than that of LL. This difference was significant (P
British Poultry Science Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/cbps20
Further investigations on protein requirement of genetically lean and fat chickens a
B. Leclercq & G. Guy
a
a
Station de Recherches Avicoles , I.N.R.A. , Nouzilly, 37380, France Published online: 08 Nov 2007.
To cite this article: B. Leclercq & G. Guy (1991) Further investigations on protein requirement of genetically lean and fat chickens, British Poultry Science, 32:4, 789-798, DOI: 10.1080/00071669108417404 To link to this article: http://dx.doi.org/10.1080/00071669108417404
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/ page/terms-and-conditions
British Poultry Science (1991) 32: 789-798
FURTHER INVESTIGATIONS ON PROTEIN REQUIREMENT OF GENETICALLY LEAN AND FAT CHICKENS B. LECLERCQ AND G. GUY Downloaded by [University of Illinois at Urbana-Champaign] at 21:08 15 March 2015
Station de Recherches Avicoles, I.N.R.A., 37380 Nouzilly, France Received for publication 17th November 1990
Abstract 1. Genetically lean (LL) or fat (FL) chickens were fed from 28 to 42 d of age on one of 6 diets with different protein contents (from 73 to 208 g/kg). In order to keep a constant amino acid balance the experimental diets were made by diluting a well-balanced proteinrich diet with a protein-free diet. 2. Dietary protein influenced the growth rate of both genotypes similarly. However, maximum weight gain was reached in LL at a lower protein intake than in FL. 3. Regression between total protein gain (body protein + feather protein) or body protein gain and protein intake exhibited significantly different slopes, that of LL being superior to that of FL. 4. At a given protein intake, feather protein gain was also superior in LL to FL. Moreover feather protein, as a percentage of total protein gain, was superior in LL to FL. When the dietary protein fell below 126 g/kg, feather protein represented a higher proportion of total protein gain. 5. Multiple linear regressions of protein intake (as the dependent variable), and body weight and protein gain or weight gain (as the independent variables) suggest that the maintenance requirement for protein is similar in both lines but that the protein efficiency for growth is significantly superior in LL. 6. In a second experiment both genotypes were offered either a single high protein diet (232 g/kg) or a single medium protein diet (186 g/kg) or had free-choice between a high (269 g/kg) and a low protein (145 g/kg) diet. In free-choice feeding, FL chickens selected an overall dietary protein content which was significantly lower (179 v. 200 g/kg) to that of LL. In both genotypes, free-choice feeding led to fatter and less efficient chickens than predicted by the linear regression between adiposity or food conversion and protein content. INTRODUCTION
Genetically lean and fat chickens from several experimental lines have been found to exhibit different protein gain to protein intake ratios, the lean 789
Downloaded by [University of Illinois at Urbana-Champaign] at 21:08 15 March 2015
790
B. LECLERCQAND G. GUY
genotype always having the better efficiency (Pym and Farrell, 1977; Leclercq, 1983; Whitehead and Griffin, 1984; Sorensen et al, 1983; Geraert et al, 1990). This was shown using frequently only one diet (Pym and Farrell, 1977; MacLeod et al, 1988; Sorensen et al, 1983; Whitehead and Griffin, 1984) and sometimes using several diets with different protein contents (Leclercq, 1983; Whitehead and Parks, 1988; Geraert et al, 1990). However, in this last situation, the protein content was modified by varying the respective proportions of cereal, soyabean meal and fat, so that amino acid profiles varied simultaneously. The present experiments were undertaken: (1) to compare diets with different protein contents but with similar amino acid profiles in order to be able to distinguish the difference in protein requirement for either maintenance or protein deposition; (2) to look for the ability of the fat and lean genotypes to adjust their protein consumption when they are offered two diets with different protein contents. MATERIALS
Birds came from fat and lean lines selected in our laboratory since 1976 (Leclercq, 1988); they belonged to the 10th generation. Only males were used in both experiments. Chicks all exhibited fast feathering. Experiment 1: Chickens were fed on a common starter diet from hatching to 28 d of age when the experimental period started. Birds (10 to 12 per treatment) were placed in individual cages in a temperature-controlled room (22°C constant). They were offered one of the 6 experimental diets made by mixing differing proportions of 2 basal diets, a protein-rich diet and a proteinfree diet, whose compositions are presented in Table 1. The 6 mixtures were calculated to contain 6 different crude protein concentrations, varying from 70 to 200 g/kg. The protein-rich diet contained some synthetic amino acids so that it had the 'ideal' profile according to the requirements suggested by Boorman and Burgess (1985). Diets were given ad libitum as pellets (2-5 mm diameter). At the beginning of the experimental period (28 d of age) 10 birds per genotype were killed to determine their body composition. The experimental period lasted 14 d (28 to 42 d of age). At the end of this period all chickens were killed by pentothal injection. All birds were plucked just after death. Feather weight was determined by weighing birds before and after plucking. Moreover, feather samples were kept to determine their dry matter and their protein contents. Plucked chickens were frozen until analysis. Body composition was determined after grinding each bird twice. Samples of ground material were freeze-dried. Lipid content was measured by ether extraction. Protein content was measured as nitrogen by a Kjeldahl procedure. Experiment 2: Chickens were given the same starter diet as in experiment 1 until 14 d of age. They were then placed in individual cages in a temperaturecontrolled room (22°C). Three treatments were compared from 14 to 49 d of age: a single high protein diet (232 g/kg), a single medium protein diet (186 g/kg), a free-choice between two diets differing in their protein contents (145
791
PROTEIN REQUIREMENT OF LEAN AND FAT CHICKENS TABLE 1 Composition of basal diets (g/kg)
Experiment 1
Downloaded by [University of Illinois at Urbana-Champaign] at 21:08 15 March 2015
Protein diet Maize Maize starch Straw Rapeseed oil Soyabean meal Soyabean protein Calcium carbonate Dicalcium phosphate Salt Trace minerals Vitamins DL-methionine L-lysine L-threonine L-histidine L-valine AMEn (calculated) (MJ/kg) Crude protein (measured)
400 120 40 250 130 10 20 4 1 5
4-55 2-30 1-00 0-33 0-29 13-08
Experiment 2
Energy diet
Low protein diet 860
820 99 40 105 10 20 4 1 5
10 15 5 1 5
13-08
259
0
12-75 145
High protein diet 542
20 250 150 10 15 5 1 5 3
12-79 269
TABLE 2 Crude protein content of experimental diets (g/kg), as determined
Experiment 1 Diet 1 Diet 2 Diet 3 Diet 4 Diet 5 Diet 6
73 102 126 152 180 208
Experiment 2 Single diet A Single diet B Free choice low protein diet high protein diet
186 232 145 269
or 269 g/kg). Food troughs were always in the same relative positions for the choice fed birds. All diets were fed as pellets (2*5 mm diameter). Broilers were weighed and slaughtered at the end of the experimental period. Abdominal fat was measured. Each treatment consisted of 14 chickens. Food consumptions were individually measured each week in the free-choice treatment and for the whole experimental period for the single diet treatments. The protein contents of the experimental diets are summarised in Table 2. Single diets were made by mixing appropriate proportions of the two diets used for the free-choice feeding treatment.
RESULTS
Live weight, body composition and food consumption of experimental groups are presented in Table 3. As the protein content increased from 73 to 180 g/kg> growth rate of both genotypes increased. No difference was ob-
792
B. LECLERCQAND G. GUY TABLE 3
Live weight (g), body composition (g) and food consumption (g) of lean and fat male chickens during the experimental period (experiment 1) Age (d) 28
Dietary protein Line LL
(gAg)
FL
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42
73
102
[
J
Ir
LL FL LL
J
FL
126
{ \
LL
J
FL
{ 152
f
LL
J
FL
180
1[
J
I 208
[
LL FL LL
J
FL
{ 1
Food consumption (28-42 d)
Live weight 459-3 (43-4)1 466-8 (40-8)
Feather protein 11-24 (1-06) 11-10 (0-97)
Body protein 75-11 (7-10) 73-74 (6-44)
702-5 (85-4) 719-7 (113-5)
20-74 (2-40) 18-72 (2-96)
93-45 (11-70) 93-39 (13-70)
139-4 (27-10) 176-0 (36-40)
1066 (182-4) 1177 (182-0)
744-6 (103-6) 767-9 (127-4)
24-02 (3-08) 20-86 (4-20)
110-54 (18-32) 104-57 (20-40)
104-1 (23-91) 157-4 (26-79)
1088 (160-1) 1160 (200-5)
851-8 (130-9) 869-7 (157-8)
26-41 (4-12) 23-12 (4-54)
128-40 (19-91) 123-10 (22-22)
110-0 (31-30) 169-9 (42-11)
1172 (163-0) 1252 (244-9)
998-1 (115-7) 964-9 (150-6)
32-39 (4-75) 27-43 (4-40)
150-45 (22-93) 135-70 (22-93)
118-9 (27-50) 170-2 (27-89)
1274 (135-3) 1306 (188-4)
1080-5 (111-2) 1069-5 (91-6)
35-30 (4-23) 31-78 (2-71)
166-21 (22-94) 152-40 (16-32)
120-6 (28-71) 182-2 (19-00)
1300 (146-4) 1441 (144-6)
1068-1 (119-4) 1067-0 (122-2)
36-73 (6-45) 33-64 (3-73)
165-80 (18-43) 157-10 (18-04)
100-7 (23-19) 169-8 (17-23)
1257 (116-2) 1383 (158-6)
Lipids 33-61 (3-15) 54-91 (4-82)
Standard deviation.
served between genotypes when weight gain was plotted against dietary protein content (data not shown). However, when weight gain was plotted against protein intake (g/kg live weight) the slope of the regression of the lean genotype (LL) was steeper than that of the fat genotype (FL) and the plateau was reached at a lower protein intake in LL than in FL (data not shown). Food consumption was influenced by the dietary protein content, increasing as protein increased and tending to plateau (or slightly decrease) beyond a dietary protein content of 152 g/kg. FL always exhibited a higher lipid content and lower body protein and feather protein contents than LL chickens. Changes in total protein gain (body protein + feather protein), body protein gain and feather protein gain as functions of protein intake are presented in Figs 1, 2 and 3, respectively. Regression coefficients of total protein gain v. protein
793
PROTEIN REQUIREMENT OF LEAN AND FAT CHICKENS lew
—
100c
g.
/'
80-
c
proi
5
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/
/ 60-
o
40-
/
/
n / •
/
i
\
100
200
300
Protein intake ( g )
FIG. 1.—Relationship between total protein gain and protein intake of FL (•) or LL (p) chickens between 28 and 42 d of age (experiment 1). lOO-i D--D
c
'5 6 0 c °a>
o
40-
T3 O
m 20-
I 100
\ 200
300
Protein intake ( g )
FIG. 2.—Relationship between body protein gain and protein intake of FL (•) or LL (•) chickens between 28 and 42 d of age (experiment 1).
intake were significantly different between FL and LL (F = 5-01), that of LL being higher than that of FL. The respective equations were: LL: total protein gain (g) = 0-5661 (±0-0272) protein intake (g) - 15-88 "r= 0-945 FL: total protein gain (g) = 0-4545 (±0-0231) protein intake (g) — 13-26 r= 0-943
794
B. LECLERCQ AND G. GUY OVJ —
20-
o Q.
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10-
s. 0-
•
i
100
•
i
200 Protein intake ( g )
300
FIG. 3.—Relationship between feather protein gain and protein intake of FL (•) or LL (n) chickens between 28 and 42 d of age (experiment 1).
Similarly different values were calculated for the coefficient of regression of body protein gain v. protein intake (F = 4-97). Regression equations were: LL: body protein gain (g) = 0-4678 (±0-0250) protein intake (g) - 17-02 r = 0-933 FL: body protein gain (g) = 0-3739 (±0-0203) protein intake (g) - 13-33 r = 0-936 Lastly regression lines of feather protein gain v. protein intake did not exhibit significantly different slopes (F = l-70). However, these lines were significantly distant (F = 46-6), LL always being superior to FL. Multiple linear regressions were calculated between protein intake (g/d) as the dependent variable and mean live weight (kg) and total protein gain (g) as the independent variables. Calculations were made excluding data from diet 6 (208 g protein/kg) because it led to a non-linear response. These equations were: LL: protein intake (g/d) = 6-04 (±0-85) live weight (kg) + 1-357 (±0-101) protein gain (g) R2 = 0-895 r.s.d. = 1-365 g/d FL: protein intake (g/d) = 6-07 (±0-98) live weight (kg) + 1-747 (±0-132) protein gain (g) R2 = 0-886 r.s.d. = 1 -658 g/d The coefficients of live weight were not different between genotypes, whereas the coefficient of protein gain was lower in LL than in FL. Similar equations were calculated using body protein instead of live weight. This led to similar conclusions, the coefficients of body protein (maintenance requirement) being similar in both genotypes. Lastly, equations were calculated using mean live weight and weight gain as independent variables. Treatments exhibiting the
795
PROTEIN REQUIREMENT OF LEAN AND FAT CHICKENS
wo — c
*-
2 a.
p \
0-5-
o
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\
-
s. 0-3c ID
s
\ \
~5 0-4-
\ n ~ * ———.
•—
•
0-2-
tt>
c •-
o 0-1 u
1
• 1 100 200 Protein intake (g)
•
300
FIG. 4.—Feather protein as proportion of total protein gain in FL (•) and LL (•) chickens according to protein intake (experiment 1).
TABLE 4
Growth performance between 24 and 49 d of age and abdominal fat proportion at 49 d of lean (LL) and fat (FL) male chickens given a high or low protein diet or choice between a high and a low protein diet (experiment 2)
Single diet B (232 g protein/kg) Live weight gain (g) Food conversion Live weight at 49 d of age (g) Abdominal fat/live weight Single diet A (186 g protein/kg) Live weight gain (g) Food conversion Live weight at 49 d of age (g) Abdominal fat/live weight Free choice (two diets) Live weight gain (g) Food conversion Live weight at 49 d of age (g) Abdominal fat/live weight Selected overall protein content (g/kg)
FL
LL
1066 (127) 2-09 (0-09) 1310 (177) 0-0253 (0-0048)
1185 (121) 1-88 (0-11) 1440 (148) 0-0050 (0-0020)
1067 (136) 2-16 (0-14) 1301 (179) 0-0341 (0-0085)
989 (99) 2-09 (0-09) 1243 (143) 0-0104 (0-0039)
1098 (140) 2-26 (0-10) 1325 (177) 0-0412 (0-0065) 176(31-5)
998(152) 2-16 (0-18) 1255 (172) 0-0112 (0-0048) 204 (39-5) < = 2-02
Analysis of variance (F value)
Weight gain Food conversion Live weight at 49 d Abdominal fat/live weight
Line effect (d.f.: 1,78) 0-50 22-5 0-0 426
Dietary effect (d.f.: 2,78) 4-38 24-0 3-05
Interaction (d.f.: 2,78) 6-00 2-47 3-17
29-3
5-70
Standard residual deviation 130-2 0-122 166-7 0-547
796
B. LECLERCQAND G. GUY
lowest and the highest protein content were excluded because they deviated from linearity. Equations were:
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LL: protein intake (g/d) = 4-49 (±1*19) live weight (kg) + 0-2805 (±0-0241) weight gain (g) i?2 = 0-907 r.s.d. = 1-12 g/d FL: protein intake (g/d) = 3-89 (±1-63) live weight (kg) + 0-3274 (±0-0327) weight gain (g) i? 2 -0-870 r.s.d. = 1-53 g/d The results from experiment 2 are given in Table 4. The weight gain of the FL was not modified by dietary treatment, whereas that of the LL was significantly lower on the low protein diet and on the free-choice diets. Overall, the dietary protein content of FL chickens offered the choice between a low and a high protein diet was significantly lower (179 g/kg) than for LL chicken (200 g/kg)- This difference occurred from the second week of the experimental period (172 v. 193 g/kg) and it was significant during the second and the fourth weeks (176 v. 204 g/kg). Lowering the dietary protein content induced an increase of fattening and of food conversion in both genotypes; however, these two parameters were higher for the free-choice diets than predicted by linear regressions calculated from single diets. Correlations between weekly selected overall dietary content of FL and LL chickens offered free-choice diets are given in Table 5. Correlations between selected dietary content during the first (21 to 28 d of age) and following weeks for the whole experimental period were very poor and not significant. Conversely, correlations between weekly selected dietary protein contents of the following weeks were very significant. TABLE 5
Correlations between weekly selected overall dietary protein content of fat (FL) and lean (LL) chicken offered a choice of low and high protein diets
2nd week 3rd week 4th week Total
1st week 0-318 0-079 0-002 0-302
2nd week
3rd week
4th week
0-591' 0-6611 0-8551
0-6931 0-8621
0-8661
1
Significant at the 001 level. Selected dietary protein content were 192 and 200 (1st week), 172 and 193 (2nd week), 179 and 201 (3rd week) and 176 and 204 g/kg (4th week) for FL and LL, respectively. DISCUSSION
The relative sensitivity of fat and lean chickens to dietary protein is controversial. Leclercq (1983) observed that the growth rate of chickens from the LL is significantly reduced when their dietary protein content fell below 191 g/kg, whereas that of FL is not modified between 152 and 211 g/kg. This observation confirmed previous work from Touchburn et al. (1981) using the same experimental lines. The results from the present experiment 2 lead to the
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PROTEIN REQUIREMENT OF LEAN AND FAT CHICKENS
797
same conclusion. However, Geraert et al. (1990), comparing these two lines, did not find different sensitivities to dietary protein. A similar observation has been made in the present experiment 1. Whitehead and Parks (1988) and Whitehead (1990) compared the growth rates of two experimental lines selected for low (lean line) or high (fat line) plasma VLDL (very low density lipoprotein) concentration as a function of dietary protein content. They did not observe a higher sensitivity of their lean genotype to low protein content. Discrepancies between all these observations might be caused by a specific requirement of the lean genotype for one or more amino acids, because aminoacid profiles were not kept constant in most of the experiments and because in the lean genotype feather protein represents a higher proportion of total protein gain than in the fat genotype. This may result in differing requirements for amino acids. LL chickens were found to be better users of dietary protein to make both feather and body (muscles and organs) protein at any given protein intake. This higher yield of LL is not the result of a lower maintenance requirement for protein because both genotypes exhibited similar maintenance requirements whatever the way of expressing this requirement. In contrast, the requirement for protein gain was always lower in LL than in FL. This led to a lower protein requirement per g of weight gain. The slope of the regression between protein gain and protein intake is significantly higher in LL than in FL confirming our previous observation (Leclercq, 1983). One explanation of this genetic control of protein utilisation could be different partitioning of amino acids, the fat chickens using more amino acid carbon to make fatty acids (Saunderson, 1988). The hormonal control of this different use of amino acids for proteinogenesis or lipogenesis needs to be investigated more precisely. LL chickens were also able to synthesise more feather protein than FL. This confirms a similar observation from Whitehead and Griffin (1985) in their own experimental lines. In our lines this cannot be explained by a difference in the fast-feathering gene because both genotypes were selected for fast-feathering (kk) from the F3 generation and because all chickens were controlled from hatching in the present experiment. We must conclude that both feather protein and body protein are synthesised in greater amounts in LL chickens. Moreover, the present experiment suggests (Fig. 4) that feather protein synthesis has priority over body protein synthesis when protein intake is reduced. This priority occurred in the present experiment when dietary protein content was lower than 126 g/kg (ideal protein). When offered a choice between a low and a high protein diet, FL chickens selected a mixture whose protein content was 20 g/kg lower than that of LL. This difference was significant (P
