- Email: [email protected]
Selection for Body Weight at Eight Weeks of Age
RESTRICTED FEEDING AND DEBEAKING
REFERENCES Aitken, J. R., H. W. W. Meyer, L. Griesbach and E. S. Merritt, 1963. Performance of heavy-type layers on a low energy ration. Can. J. Anim. Sci. 4 3 : 290-293. Bray, D. J., S. F. Ridlen and J. A. Gesell, 1960. Performance of pullets debeaked at various times during the laying year. Poultry Sci. 39: 1546-1550. Combs, G. F., B. Gattis and C. S. Shaffner, 1961. Studies with laying hens. 2. Energy restriction. Poultry Sci. 40: 220-224. Donaldson, W. E., and R. I. Millar, 1962. Effects of energy restriction on laying hens. Poultry Sci. 4 1 : 353-359. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1^2. Hargreaves, R. C , and L. R. Champion, 1955. De-
beaking of caged layers. Poultry Sci. 44: 12231227. Heywang, B. W., 1940. The effect of restricted feed intake on egg weight, egg production and body weight. Poultry Sci. 19: 29-34. Lonsdale, M. B., R. M. Vondell and R. C. Ringrose, 1957. Debeaking at one day of age and the feeding of pellets to broiler chickens. Poultry Sci. 36: 565-571. Sherwood, D. H., and T. T. Milby, 1961. Controlled feeding of laying chickens. Poultry Sci. 40: 80-86. Sherwood, D. H., C. D. Caskey, B. A. Krautmann, M. C. Van Wormer, S. B. Smith and R. E Ward, 1964. Management and feeding of meattype breeder chickens. Poultry Sci. 43: 12721278. Singsen, E. P., 1962. Feeding broiler type breeding hens. Proceedings Maryland Nutrition Conference for Feed Manufacturers, pp. 5-8 Singsen, E. P., L. D. Matterson, J. Tlustohowicz and L. M. Potter, 1959. The effect of controlled feeding, energy intake and type of diet on the performance of heavy-type laying hens. Storrs (Connecticut) Agr. Expt. Sta. Bull. 346. Slinger, S. J., and W. F. Pepper, 1964. Effects of debeaking and feeding whole grain on the reproductive performance of pullets. Poultry Sci. 43: 356-362. Snedecor, G. W., 1956. Statistical Methods. Fifth edition, Iowa State College Press, Ames, Iowa. Vondell, R. M., and R. C. Ringrose, 1957. Debeaking at one day of age and the feeding of pellets to broiler chickens 2. Poultry Sci. 36: 13101312.
Selection for Body Weight at Eight Weeks of Age 6. CHANGES IN APPETITE AND FEED UTILIZATION P. B. SIEGEL AND E. L. WISMAN Virginia Polytechnic Institute, Blacksburg, Va. (Received for publication May 12, 1966)
"DIDIRECTIONAL selection experiments •*-" for juvenile growth of chickens have demonstrated that mean body weight at time t may be readily changed beyond the limits of the base population (Schnetzler, 1936; Maloney et al., 1963; Gyles and Thomas, 1963). Lacking, however, is in-
formation concerning changes that occur in factors influencing growth. Some attempts have been made to investigate the nutritional physiology of the lines derived from the two-way selection experiment for eight-week weight by Siegel (1962). Siegel and Wisman (1962) ob-
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on May 10, 2015
the first experiment a decrease in production was noted when feed was withheld for 24 or 39 consecutive hours per week. Debeaking reduced feed consumption and body weight gain. A significant improvement in percent fertility was observed in the first experiment for the non-debeaked as compared with the debeaked birds. The results would suggest that while debeaking may reduce feed consumption and body weight gain, such benefits may be counterbalanced by a reduction in fertility.
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P . B . SlEGEL AND E . L. WlSMAN
Fowler (1962) has shown differences in food consumption as a primary influence in mice selected for large and small body size. A similar conclusion was made by Lepore (1965a,b) for lines of chickens selected for high and low methionine requirements. We may reason that an increased appetite in a high-weight line and a decreased appetite in a low-weight line could mask concomitant changes in feed utilization. This is because the more efficient line could show poor feed utilization in an ad libitum feeding situation due to over consumption of foodstuffs. This paper provides information on this hypothesis. The first experiment was designed to measure energy and protein utilization in lines selected bidirectionally for high and low body weight when feed was provided ad libitum. The second experiment consisted of comparisons between lines when feed consumption was comparable for both lines. This facilitated an assessment of changes in appetite and nutritional physiology concomitant to selection for body weight at eight weeks of age. METHODS AND MATERIALS
Stocks. Chicks used in these experiments
were obtained from F 5 generation matings of White Plymouth Rocks that had been selected in opposite directions for body weight at eight weeks of age. Siegel (1962) has described details on selection procedures and responses in the development of these lines. Briefly, both lines, high-weight (HW) and low-weight (LW), originated from a common gene pool derived from crosses of several inbred lines. Selection within each line was made on an individual bird basis for the single trait, body weight at eight weeks of age. Matings were partially restricted to minimize the effects of inbreeding. Diets. The experimental diets employed in the two experiments are described in Table 1. Diet A was considered as the basal control diet and the other four were formulated to reflect the changes in protein and/or energy levels without altering the contents of other necessary nutrients. In all diets the latter were considered to be adequate for maximum growth. Experiment 1. This experiment utilized two lines (HW and LW) and four diets (B, C, D, and E) in each possible combination. Each diet-line treatment was replicated three times giving a total of 24 experimental pens (12 <$ J1 chicks per pen). Conventional batteries with raised wire floors were used. Upon hatching and sexing, the males were fed basal diet A to one week of age at which time they were individually weighed and randomly assigned to the 24 pens to begin the experiment. Feed and water were supplied ad libitum. At one week of age four chicks from each line were sacrificed for an analysis of initial body composition. At the end of the three-week experimental period two chicks were randomly selected from each pen (6/line/ration) and sacrificed for final body composition. Change in carcass composition during the experimental period was obtained by subtraction of the initial
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served that decreases in protein and energy levels below that at which selection was practiced reduced body-weight gains for males and females in both lines. Protein and energy levels above those employed during selection resulted in increased growth responses for males of both lines but not females. Subsequently, Wisman and Siegel (1963) defined more precisely the protein and energy requirements for males and females in these lines. The data in both reports suggested that utilization of feed was more efficient in the high line than in the low line. Further evidence for greater utilization efficiency by embryos in the high line was observed for specific amino acids by Lepore et al. (1963).
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SELECTION FOE BODY WEIGHT TABLE 1.—Composition of diets D Ground yellow corn Soybean meal, 50% protein Hydzd. animal and vegetable fat Solka-floc (cellulose) Constant ingredients1
Kg. 45.2 33.0 9.5
Kg. 62.0 24.3
—
1.4 12.3
12.3 100
—
100
Kg. 45.0 27.0 15.7
—
12.3 100
Kg. 45.5 39.0 3.2
—
12.3 100
Kg. 25.3 42.3 20.1
—
12.3 100
Calculated analysis 22.6 3.1
19.7 2.8
19.7 3.4
25.6 2.8
25.6 3.4
1 Contained the following: 5 kg. condensed fish solubles, 2.5 kg. dehydrated alfalfa meal, 2 kg. dicalcium phosphate, 1 kg. ground limestone, 444 g. trace mineralized NaCl, 128 g. trace mineral mix, 22 g. manganese sulfate, 4 g. zinc carbonate, 150 g. DL-methionine, 50 g. chlortetracyclme, 804,000 I.U. vitamin A, 86,000 I.C.U. vitamin D 3 , 975 I. U. vitamin E, 41.1 g. choline CI, 12.5 g. ethoxyquin, 4.4 g. niacin, 1.6 g.d-calcium pantothenate, 111 mg. sodium menadione disulfite, 884 mg. riboflavin, 66 mg. folic acid, 11 mg. biotin 1.3 mg. vitamin B12 and corn meal to make up to 12.3 kg.
mean value for each line from the final individual value for birds in that respective line. Chicks were killed by cervical fracture without blood loss and then frozen. Subsequently they were ground in the frozen state, freeze-dried, reground and sampled for nitrogen and energy determinations. Nitrogen was determined by the macroKjeldahl method and energy by bomb calorimetry. Total excreta for each pen was collected daily, frozen and stored. Later the total excreta was blended, sampled, freeze-dried, and analyzed for nitrogen and energy. A preliminary comparison of excreta collected daily in acid with that collected on plastic showed no difference in nitrogen content; therefore, the collection in acid to reduce loss of NH 3 was not found to be necessary and the dropping pans were merely covered with plastic. Gains in body weight during the experimental period were obtained by subtraction of initial from final weight. Gains in body weight were analyzed on an individual bird basis and all data were analyzed by analysis of variance. Experiment 2. Two-hundred cockerels
from the HW and LW lines were grown in conventional batteries with raised wire floors from hatching to one week of age. All were fed basal diet (A) ad libitum. At one week of age the chicks were weighed individually and those more than one standard deviation from the mean for its line were discarded. Twenty-eight of the remaining males within each line were then assigned at random to each experimental diet (B, C, D, and E) and within each diet the seven HW birds were paired with the seven LW birds. Each chick was maintained in an individual wire compartment and provided with its own feed. Paired-feeding was employed with the HW individual being restricted to the amount of feed eaten by its paired LW mate on the previous day. Because differences between lines existed for body weight at hatching, (Lepore et al., 1965) and persisted throughout life (Siegel, 1963) birds could not be paired by weights without using opposite extremes from the lines. The mean range in differences between pairs at one week of age was 19 g. Since feed is used for both growth and maintenance, additional feed would be
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Crude protein, % M. energy, kcal./g.
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P . B . SlEGEL AND E . L. WlSMAN
TABLE 2.—Gain in body weight, feed consumption
and feed efficiency from 1 to 4 weeks {Experiment 1) Line
Protein,
%
M . energy, kca!./g.
HW LW diff
Wt. (g.)
Consump. (g.)
Effic.
312 214
651 444
.479 .482
98" 19.7 25.6
263 259
diff 2.8 3.4
107**
-.003
550 536
.478 .483
4
14
-.005
262 260
555 532
.472 .489
2
23
-.017
2.8 3.4
258 269
563 539
.458 .499
25.6 25.6
2.8 3.4
266 251
547 525
.486 .478
**p<.01. The interaction, protein-energy, shown below the line was significant (p<.05) for body weight and feed efficiency.
needed by the HW chick for maintenance of its larger body. To compensate for this, each chick was weighed daily and the feed allotment for the HW chick was proportioned to its weight in relation to its LW counterpart. Thus, if a 100 g. LW chick consumed 20 g. of feed its 120 g. HW pair was given 24 g. This calculation was made daily. Growth was measured as gain in body weight from 1 to 4 weeks of age and feed efficiency was measured as g. gain in weight per g. feed consumed during this same period. Analyses of body gains and feed efficiencies were made by paired t tests. RESULTS AND DISCUSSION Primary emphasis in this report will be given to the genetic and genetic-nutritional aspects rather than the nutritional phases of the study. Experiment 1. Mean gains in body weight, feed consumption and feed efficiency by lines and diets are presented in Table 2. Highly significant differences were found between lines for body gains with HW males gaining more weight than LW males. This was expected from our prior work
Differences between dietary variables were not significant as measured by growth, feed consumption and efficiency (Table 2). Further, the line-protein and line-energy interactions were not significant. The lack of significant line-dietary variable interactions was consistent with prior results for these lines (Siegel and Wisman, 1962). Protein. Since the HW birds were larger and consumed more feed than LW birds, the expectation would be for a greater consumption of protein and a greater deposition of protein in the carcass of the HW than the LW birds. That this did occur is seen by the highly significant differences between lines for protein, as measured by nitrogen (Table 3). There was also a highly significant difference between lines for nitrogen excreted, with the mean for the HW line being larger than that for the LW line. Although lines differed significantly on an absolute basis for carcass and excreta nitrogen, they were not significantly differ-
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diff 19.7 19.7
(Siegel and Wisman, 1962; Wisman and Siegel, 1963). There was a highly significant difference between lines for feed consumption, with males in the HW line consuming more feed than the LW males. This suggests that selection for body weight resulted in concomitant changes in feed consumption and agrees with Fowler (1962) who observed that feed intake was higher in a line of mice selected for large body size than in a line selected for small body size: No significant differences were found between the HW and LW lines for feed efficiency (body gain -=- feed consumption). Feed efficiency is a function of body gain and feed consumption, therefore when feed is provided ad libitum, as in this experiment, efficiency may be biased if selection for increased weight is largely a selection for appetite as suggested by Lepore (1965a,b). Experiment 2, of the present study removes this potential bias.
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SELECTION FOR BODY WEIGHT TABLE 3.—Nitrogen values, 1 to 4 weeks {Experiment 1)
Line
Protein
%
M. energy, kcal./g.
HW LW diff
g.N
Loss Consumed
Carcass
Excreta
Carcass
Excreta
249.3 182.2
100.7 74.7
133.9 101.6
40.8 41.4
53.5 55.4
5.7 3.2
-.6
-1.9
2.5
45.6 36.7
51.5 57.5
2.9 5.8
67.1** 19.7 25.6
% of N consumed in
26.0**
32.2**
89.4 86.0
101.0 134.5
-37.9**
3.4
-33.5**
2.8 3.4
220.7 210.8
89.3 86.2
123.1 112.4
diff
9.9
3.1
diff
10.7*
8.9**
-6.0**
-2.9
40.7 41.6
55.4 53.5
3.9 4.9
-.9
1.9
-1.0
*p<.05. **p<.01. The interaction, protein-energy, was significant for % N in excreta and highly significant for % N in carcass.
ent when expressed as a percentage of nitrogen consumed. There was a highly significant difference between protein levels for nitrogen consumption, with the mean for the 25% protein diet being larger than that for the 19% diet (Table 3). The additional nitrogen was not deposited in the carcass but was voided, as indicated by the nonsignificant difference between diets for carcass nitrogen and the highly significant difference between them for excreta nitrogen. This result was consistent with a prior observation based on growth assays where 19% crude protein was adequate for both lines (Wisman and Siegel, 1963). Retention of the nitrogen consumed was more efficient at the lower protein level as evidenced by the highly significant differences between lines for percentage nitrogen consumed in the carcass and excreta. Energy levels had no significant effect on either nitrogen consumed or nitrogen deposited in the carcass, however significantly more nitrogen was found in the excreta of birds fed the low energy ration. Expression of carcass and excreta nitrogen as a percentage of nitrogen consumed yielded no significant difference between energy levels.
These results were consistent with those of Yoshida et al. (1962) who observed a marked influence of dietary protein on nitrogen retention whereas the effect of dietary energy was very small. No significant interactions of lines-energy and lines-protein were found for any of the nitrogen values given in Table 3. Energy. Consistent with the greater feed intake was a greater consumption of energy by HW than by LW birds with the differences between lines being highly significant (Table 4). Carcass energy was also greater for birds from the HW than the LW line with the difference between lines being highly significant. The percentage of calories consumed that was retained in the carcass was not different between the lines. Metabolizable energy was comparable for both the HW and the LW lines. Although there was no difference between dietary protein levels for energy consumed, significantly more energy was deposited and retained in the carcass of the birds fed the lower protein level. This difference may be due to fat deposition. The significantly higher metabolizable energy levels observed with the 19% rations
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196.8 234.7
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P . B . SlEGEL AND E . L. WlSMAN TABLE 4.—Energy values, 1 to 4 weeks (Experiment 1)
Line
Protein, %
M. energy, kcal./g.
kcal. consumed
29,837 21,717
HW LW diff
8,120** 26,070 25,484
19.7 25.6 diff
586
kcal. carcass
5,848 4,086 1,762** 5,442 4,492 950**
% kcal. retained in carcass 19.7 19.0
Metabolizable energy kcal./g. feed1 3.40 3.42
.7
-.02
21.0 17.7
3.48 3.33
3.3**
.15**
22,995 28,560
4,777 5,157
diff
-5,565**
-380*
HW
2.8 3.4
26,195 33,479
5,409 6,287
20.6 18.8
3.12 3.68
LW
2.8 3.4
19,793 23,640
4,144 4,027
21.0 17.0
3.16 3.67
20.8 17.9 2.9**
3.14 3.68 -.54**
*P<.05. ** P < . 0 1 . The interaction line-energy shown below the line was highly significant for kcal consumed and kcal deposited in carcass; protein-energy was highly significant for metabolizable energy. kcal. consumed—kcal. in excreta l ME = . g. feed consumed
may reflect greater fat and protein metabolism. Consumption and deposition of energy were greater for the higher energy diet than for the lower energy one. Since body weight and nitrogen retention were comparable for both energy levels, this would suggest more fat and less water in chicks fed the higher energy rations than in those fed the lower energy rations. This line-energy interaction was highly significant for energy consumed and deposited in the carcass (Table 4). Twentyeight percent more energy was consumed by HW birds fed the high energy ration than was consumed by those fed the lower energy ration. In the LW line the percentage increase was 19. Energy deposited in the carcass of HW birds increased with an increase in energy level of the ration whereas no change occurred in the LW line.
These results show that appetite as measured by feed consumption changed concomitantly with selection for body weight. Since feed was provided ad libitum, the birds in the HW line were afforded the opportunity for overconsumption which would cause a bias in measuring the utilization of feed. To remove this bias the paired feeding experiment was conducted. Experiment 2. Mean gains in body weight and feed efficiencies from 1 to 4 weeks of age are presented in Table 5. Gains in body weight were greater for birds in HW line than in the LW line where feed consumption in the former was restricted to that of the latter. Although the degree of significance for the difference between lines for body weight varied with the diet, all were significant at the P < .1 level. Significant differences in feed efficiency (P < .05) were found between lines
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2.8 3.4
SELECTION FOE BODY WEIGHT TABLE 5.—Gain in body weights and feed efficiencies from paired feeding, 1 to 4 weeks (Experiment Z) Effic.
Wt. (g.)
B C D E
HW
LW
Diff
HW
LW
Diff
304 356 322 311
262 252 251 252
48t 104" 71*» 601
.479 .528 .533 .547
.467 .464 .488 .494
.022 .074* .045* .053*
tp<.l. * P<.05 **P<.01
SUMMARY
Two experiments were conducted to measure appetite and feed utilization as influenced by selection for large and small body weight in chickens. The results show that selection for body weight was positively associated with the efficiency of feed utilization and appetite. This demonstrated further that changes in appetite could mask associated changes in feed utilization unless the former is controlled. REFERENCES Gyles, N. R., and J. E. Thomas, 1963. Divergent selection for eight week body weight in White Wyandottes. Poultry Sci. 42: 1273-1274.
Fowler, R. E., 1962. The efficiency of food utilization, digestibility of food stuffs and energy expenditure of mice selected for large and small body size. Genet. Res. Camb. 3 : 51-68. Lepore, P. D., 1965a. Methionine and protein requirements of lines of chickens established by growth-rate selection on a methionine deficient diet. Poultry Sci. 44: 797-803. Lepore, P. D., 1965b. Appetite and growth rate selection with a methionine deficient diet. Poultry Sci. 42: 1093-1097. Lepore, P. D., P. B. Siegel and K. W. King, 1963. Proximate and amino acid composition of eggs and chicks from growth selected lines of White Rocks. Life. Sci. 2: 584-593. Lepore, P. D., P. B. Siegel and H. S. Siegel, 1965. Nucleic acid composition of chicks and chick tissues from growth selected lines of White Rocks. Poultry Sci. 44: 126-130. Maloney, M. A., J. C. Gilbreath and R. D. Morrison, 1963. Two-way selection for body weight in chickens. Oklahoma Agr. Expt. Sta. Tech. Bull. T-99. Schnetzler, E. E., 1936. Inheritance of rate of growth in Barred Plymouth Rocks. Poultry Sci. 15: 369-376. Siegel, P. B., 1962. Selection for body weight at eight weeks of age. 1. Short term response and heritabilities. Poultry Sci. 4 1 : 954-962. Siegel, P. B., 1963. Selection for body weight at eight weeks of age. 2. Correlated responses of feathering, body weights, and reproductive characteristics. Poultry Sci. 42: 896-905. Siegel, P. B., and E. L. Wisman, 1962. Protein and energy requirements of chickens selected for high and low body weight. Poultry Sci. 4 1 : 1225-1232. Wisman, E. L., and P. B. Siegel, 1963. Further studies on protein and energy requirements of chicks selected for high and low body weights. Poultry Sci. 42: 541-543. Yoshida, M., S. Hizukuro, H. Hoshii and H. Morimoto, 1962. Effect of dietary protein and energy levels on the growth rate, feed efficiency and carcass composition of chicks. Agric. Biol. Chem. 26 : 640-646.
FEBRUARY 9-12. FACT FINDING CONFERENCE, INSTITUTE OF AMERICAN POULTRY INDUSTRIES, MUNICIPAL AUDITORIUM, KANSAS CITY APRIL 10-12. THE 27TH ANNUAL MEETING OF THE POULTRY AND EGG NATIONAL BOARD, PICK-CONGRESS HOTEL, CHICAGO
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fed diets C, D, and E with the birds in the HW line being more efficient than those in the LW line. Lepore et al. (1963) observed that the embryos in the HW line utilized certain amino acids more efficiently than the embryos in the LW line. The results obtained here demonstrate that selection for body weight was positively associated with appetite and efficiency of feed utilization. Determination of the efficiency of utilization of feed is difficult unless appetite is somehow controlled.
1397
REFERENCES Aitken, J. R., H. W. W. Meyer, L. Griesbach and E. S. Merritt, 1963. Performance of heavy-type layers on a low energy ration. Can. J. Anim. Sci. 4 3 : 290-293. Bray, D. J., S. F. Ridlen and J. A. Gesell, 1960. Performance of pullets debeaked at various times during the laying year. Poultry Sci. 39: 1546-1550. Combs, G. F., B. Gattis and C. S. Shaffner, 1961. Studies with laying hens. 2. Energy restriction. Poultry Sci. 40: 220-224. Donaldson, W. E., and R. I. Millar, 1962. Effects of energy restriction on laying hens. Poultry Sci. 4 1 : 353-359. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1^2. Hargreaves, R. C , and L. R. Champion, 1955. De-
beaking of caged layers. Poultry Sci. 44: 12231227. Heywang, B. W., 1940. The effect of restricted feed intake on egg weight, egg production and body weight. Poultry Sci. 19: 29-34. Lonsdale, M. B., R. M. Vondell and R. C. Ringrose, 1957. Debeaking at one day of age and the feeding of pellets to broiler chickens. Poultry Sci. 36: 565-571. Sherwood, D. H., and T. T. Milby, 1961. Controlled feeding of laying chickens. Poultry Sci. 40: 80-86. Sherwood, D. H., C. D. Caskey, B. A. Krautmann, M. C. Van Wormer, S. B. Smith and R. E Ward, 1964. Management and feeding of meattype breeder chickens. Poultry Sci. 43: 12721278. Singsen, E. P., 1962. Feeding broiler type breeding hens. Proceedings Maryland Nutrition Conference for Feed Manufacturers, pp. 5-8 Singsen, E. P., L. D. Matterson, J. Tlustohowicz and L. M. Potter, 1959. The effect of controlled feeding, energy intake and type of diet on the performance of heavy-type laying hens. Storrs (Connecticut) Agr. Expt. Sta. Bull. 346. Slinger, S. J., and W. F. Pepper, 1964. Effects of debeaking and feeding whole grain on the reproductive performance of pullets. Poultry Sci. 43: 356-362. Snedecor, G. W., 1956. Statistical Methods. Fifth edition, Iowa State College Press, Ames, Iowa. Vondell, R. M., and R. C. Ringrose, 1957. Debeaking at one day of age and the feeding of pellets to broiler chickens 2. Poultry Sci. 36: 13101312.
Selection for Body Weight at Eight Weeks of Age 6. CHANGES IN APPETITE AND FEED UTILIZATION P. B. SIEGEL AND E. L. WISMAN Virginia Polytechnic Institute, Blacksburg, Va. (Received for publication May 12, 1966)
"DIDIRECTIONAL selection experiments •*-" for juvenile growth of chickens have demonstrated that mean body weight at time t may be readily changed beyond the limits of the base population (Schnetzler, 1936; Maloney et al., 1963; Gyles and Thomas, 1963). Lacking, however, is in-
formation concerning changes that occur in factors influencing growth. Some attempts have been made to investigate the nutritional physiology of the lines derived from the two-way selection experiment for eight-week weight by Siegel (1962). Siegel and Wisman (1962) ob-
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on May 10, 2015
the first experiment a decrease in production was noted when feed was withheld for 24 or 39 consecutive hours per week. Debeaking reduced feed consumption and body weight gain. A significant improvement in percent fertility was observed in the first experiment for the non-debeaked as compared with the debeaked birds. The results would suggest that while debeaking may reduce feed consumption and body weight gain, such benefits may be counterbalanced by a reduction in fertility.
1391
1392
P . B . SlEGEL AND E . L. WlSMAN
Fowler (1962) has shown differences in food consumption as a primary influence in mice selected for large and small body size. A similar conclusion was made by Lepore (1965a,b) for lines of chickens selected for high and low methionine requirements. We may reason that an increased appetite in a high-weight line and a decreased appetite in a low-weight line could mask concomitant changes in feed utilization. This is because the more efficient line could show poor feed utilization in an ad libitum feeding situation due to over consumption of foodstuffs. This paper provides information on this hypothesis. The first experiment was designed to measure energy and protein utilization in lines selected bidirectionally for high and low body weight when feed was provided ad libitum. The second experiment consisted of comparisons between lines when feed consumption was comparable for both lines. This facilitated an assessment of changes in appetite and nutritional physiology concomitant to selection for body weight at eight weeks of age. METHODS AND MATERIALS
Stocks. Chicks used in these experiments
were obtained from F 5 generation matings of White Plymouth Rocks that had been selected in opposite directions for body weight at eight weeks of age. Siegel (1962) has described details on selection procedures and responses in the development of these lines. Briefly, both lines, high-weight (HW) and low-weight (LW), originated from a common gene pool derived from crosses of several inbred lines. Selection within each line was made on an individual bird basis for the single trait, body weight at eight weeks of age. Matings were partially restricted to minimize the effects of inbreeding. Diets. The experimental diets employed in the two experiments are described in Table 1. Diet A was considered as the basal control diet and the other four were formulated to reflect the changes in protein and/or energy levels without altering the contents of other necessary nutrients. In all diets the latter were considered to be adequate for maximum growth. Experiment 1. This experiment utilized two lines (HW and LW) and four diets (B, C, D, and E) in each possible combination. Each diet-line treatment was replicated three times giving a total of 24 experimental pens (12 <$ J1 chicks per pen). Conventional batteries with raised wire floors were used. Upon hatching and sexing, the males were fed basal diet A to one week of age at which time they were individually weighed and randomly assigned to the 24 pens to begin the experiment. Feed and water were supplied ad libitum. At one week of age four chicks from each line were sacrificed for an analysis of initial body composition. At the end of the three-week experimental period two chicks were randomly selected from each pen (6/line/ration) and sacrificed for final body composition. Change in carcass composition during the experimental period was obtained by subtraction of the initial
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on May 10, 2015
served that decreases in protein and energy levels below that at which selection was practiced reduced body-weight gains for males and females in both lines. Protein and energy levels above those employed during selection resulted in increased growth responses for males of both lines but not females. Subsequently, Wisman and Siegel (1963) defined more precisely the protein and energy requirements for males and females in these lines. The data in both reports suggested that utilization of feed was more efficient in the high line than in the low line. Further evidence for greater utilization efficiency by embryos in the high line was observed for specific amino acids by Lepore et al. (1963).
1393
SELECTION FOE BODY WEIGHT TABLE 1.—Composition of diets D Ground yellow corn Soybean meal, 50% protein Hydzd. animal and vegetable fat Solka-floc (cellulose) Constant ingredients1
Kg. 45.2 33.0 9.5
Kg. 62.0 24.3
—
1.4 12.3
12.3 100
—
100
Kg. 45.0 27.0 15.7
—
12.3 100
Kg. 45.5 39.0 3.2
—
12.3 100
Kg. 25.3 42.3 20.1
—
12.3 100
Calculated analysis 22.6 3.1
19.7 2.8
19.7 3.4
25.6 2.8
25.6 3.4
1 Contained the following: 5 kg. condensed fish solubles, 2.5 kg. dehydrated alfalfa meal, 2 kg. dicalcium phosphate, 1 kg. ground limestone, 444 g. trace mineralized NaCl, 128 g. trace mineral mix, 22 g. manganese sulfate, 4 g. zinc carbonate, 150 g. DL-methionine, 50 g. chlortetracyclme, 804,000 I.U. vitamin A, 86,000 I.C.U. vitamin D 3 , 975 I. U. vitamin E, 41.1 g. choline CI, 12.5 g. ethoxyquin, 4.4 g. niacin, 1.6 g.d-calcium pantothenate, 111 mg. sodium menadione disulfite, 884 mg. riboflavin, 66 mg. folic acid, 11 mg. biotin 1.3 mg. vitamin B12 and corn meal to make up to 12.3 kg.
mean value for each line from the final individual value for birds in that respective line. Chicks were killed by cervical fracture without blood loss and then frozen. Subsequently they were ground in the frozen state, freeze-dried, reground and sampled for nitrogen and energy determinations. Nitrogen was determined by the macroKjeldahl method and energy by bomb calorimetry. Total excreta for each pen was collected daily, frozen and stored. Later the total excreta was blended, sampled, freeze-dried, and analyzed for nitrogen and energy. A preliminary comparison of excreta collected daily in acid with that collected on plastic showed no difference in nitrogen content; therefore, the collection in acid to reduce loss of NH 3 was not found to be necessary and the dropping pans were merely covered with plastic. Gains in body weight during the experimental period were obtained by subtraction of initial from final weight. Gains in body weight were analyzed on an individual bird basis and all data were analyzed by analysis of variance. Experiment 2. Two-hundred cockerels
from the HW and LW lines were grown in conventional batteries with raised wire floors from hatching to one week of age. All were fed basal diet (A) ad libitum. At one week of age the chicks were weighed individually and those more than one standard deviation from the mean for its line were discarded. Twenty-eight of the remaining males within each line were then assigned at random to each experimental diet (B, C, D, and E) and within each diet the seven HW birds were paired with the seven LW birds. Each chick was maintained in an individual wire compartment and provided with its own feed. Paired-feeding was employed with the HW individual being restricted to the amount of feed eaten by its paired LW mate on the previous day. Because differences between lines existed for body weight at hatching, (Lepore et al., 1965) and persisted throughout life (Siegel, 1963) birds could not be paired by weights without using opposite extremes from the lines. The mean range in differences between pairs at one week of age was 19 g. Since feed is used for both growth and maintenance, additional feed would be
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Crude protein, % M. energy, kcal./g.
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P . B . SlEGEL AND E . L. WlSMAN
TABLE 2.—Gain in body weight, feed consumption
and feed efficiency from 1 to 4 weeks {Experiment 1) Line
Protein,
%
M . energy, kca!./g.
HW LW diff
Wt. (g.)
Consump. (g.)
Effic.
312 214
651 444
.479 .482
98" 19.7 25.6
263 259
diff 2.8 3.4
107**
-.003
550 536
.478 .483
4
14
-.005
262 260
555 532
.472 .489
2
23
-.017
2.8 3.4
258 269
563 539
.458 .499
25.6 25.6
2.8 3.4
266 251
547 525
.486 .478
**p<.01. The interaction, protein-energy, shown below the line was significant (p<.05) for body weight and feed efficiency.
needed by the HW chick for maintenance of its larger body. To compensate for this, each chick was weighed daily and the feed allotment for the HW chick was proportioned to its weight in relation to its LW counterpart. Thus, if a 100 g. LW chick consumed 20 g. of feed its 120 g. HW pair was given 24 g. This calculation was made daily. Growth was measured as gain in body weight from 1 to 4 weeks of age and feed efficiency was measured as g. gain in weight per g. feed consumed during this same period. Analyses of body gains and feed efficiencies were made by paired t tests. RESULTS AND DISCUSSION Primary emphasis in this report will be given to the genetic and genetic-nutritional aspects rather than the nutritional phases of the study. Experiment 1. Mean gains in body weight, feed consumption and feed efficiency by lines and diets are presented in Table 2. Highly significant differences were found between lines for body gains with HW males gaining more weight than LW males. This was expected from our prior work
Differences between dietary variables were not significant as measured by growth, feed consumption and efficiency (Table 2). Further, the line-protein and line-energy interactions were not significant. The lack of significant line-dietary variable interactions was consistent with prior results for these lines (Siegel and Wisman, 1962). Protein. Since the HW birds were larger and consumed more feed than LW birds, the expectation would be for a greater consumption of protein and a greater deposition of protein in the carcass of the HW than the LW birds. That this did occur is seen by the highly significant differences between lines for protein, as measured by nitrogen (Table 3). There was also a highly significant difference between lines for nitrogen excreted, with the mean for the HW line being larger than that for the LW line. Although lines differed significantly on an absolute basis for carcass and excreta nitrogen, they were not significantly differ-
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diff 19.7 19.7
(Siegel and Wisman, 1962; Wisman and Siegel, 1963). There was a highly significant difference between lines for feed consumption, with males in the HW line consuming more feed than the LW males. This suggests that selection for body weight resulted in concomitant changes in feed consumption and agrees with Fowler (1962) who observed that feed intake was higher in a line of mice selected for large body size than in a line selected for small body size: No significant differences were found between the HW and LW lines for feed efficiency (body gain -=- feed consumption). Feed efficiency is a function of body gain and feed consumption, therefore when feed is provided ad libitum, as in this experiment, efficiency may be biased if selection for increased weight is largely a selection for appetite as suggested by Lepore (1965a,b). Experiment 2, of the present study removes this potential bias.
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SELECTION FOR BODY WEIGHT TABLE 3.—Nitrogen values, 1 to 4 weeks {Experiment 1)
Line
Protein
%
M. energy, kcal./g.
HW LW diff
g.N
Loss Consumed
Carcass
Excreta
Carcass
Excreta
249.3 182.2
100.7 74.7
133.9 101.6
40.8 41.4
53.5 55.4
5.7 3.2
-.6
-1.9
2.5
45.6 36.7
51.5 57.5
2.9 5.8
67.1** 19.7 25.6
% of N consumed in
26.0**
32.2**
89.4 86.0
101.0 134.5
-37.9**
3.4
-33.5**
2.8 3.4
220.7 210.8
89.3 86.2
123.1 112.4
diff
9.9
3.1
diff
10.7*
8.9**
-6.0**
-2.9
40.7 41.6
55.4 53.5
3.9 4.9
-.9
1.9
-1.0
*p<.05. **p<.01. The interaction, protein-energy, was significant for % N in excreta and highly significant for % N in carcass.
ent when expressed as a percentage of nitrogen consumed. There was a highly significant difference between protein levels for nitrogen consumption, with the mean for the 25% protein diet being larger than that for the 19% diet (Table 3). The additional nitrogen was not deposited in the carcass but was voided, as indicated by the nonsignificant difference between diets for carcass nitrogen and the highly significant difference between them for excreta nitrogen. This result was consistent with a prior observation based on growth assays where 19% crude protein was adequate for both lines (Wisman and Siegel, 1963). Retention of the nitrogen consumed was more efficient at the lower protein level as evidenced by the highly significant differences between lines for percentage nitrogen consumed in the carcass and excreta. Energy levels had no significant effect on either nitrogen consumed or nitrogen deposited in the carcass, however significantly more nitrogen was found in the excreta of birds fed the low energy ration. Expression of carcass and excreta nitrogen as a percentage of nitrogen consumed yielded no significant difference between energy levels.
These results were consistent with those of Yoshida et al. (1962) who observed a marked influence of dietary protein on nitrogen retention whereas the effect of dietary energy was very small. No significant interactions of lines-energy and lines-protein were found for any of the nitrogen values given in Table 3. Energy. Consistent with the greater feed intake was a greater consumption of energy by HW than by LW birds with the differences between lines being highly significant (Table 4). Carcass energy was also greater for birds from the HW than the LW line with the difference between lines being highly significant. The percentage of calories consumed that was retained in the carcass was not different between the lines. Metabolizable energy was comparable for both the HW and the LW lines. Although there was no difference between dietary protein levels for energy consumed, significantly more energy was deposited and retained in the carcass of the birds fed the lower protein level. This difference may be due to fat deposition. The significantly higher metabolizable energy levels observed with the 19% rations
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196.8 234.7
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P . B . SlEGEL AND E . L. WlSMAN TABLE 4.—Energy values, 1 to 4 weeks (Experiment 1)
Line
Protein, %
M. energy, kcal./g.
kcal. consumed
29,837 21,717
HW LW diff
8,120** 26,070 25,484
19.7 25.6 diff
586
kcal. carcass
5,848 4,086 1,762** 5,442 4,492 950**
% kcal. retained in carcass 19.7 19.0
Metabolizable energy kcal./g. feed1 3.40 3.42
.7
-.02
21.0 17.7
3.48 3.33
3.3**
.15**
22,995 28,560
4,777 5,157
diff
-5,565**
-380*
HW
2.8 3.4
26,195 33,479
5,409 6,287
20.6 18.8
3.12 3.68
LW
2.8 3.4
19,793 23,640
4,144 4,027
21.0 17.0
3.16 3.67
20.8 17.9 2.9**
3.14 3.68 -.54**
*P<.05. ** P < . 0 1 . The interaction line-energy shown below the line was highly significant for kcal consumed and kcal deposited in carcass; protein-energy was highly significant for metabolizable energy. kcal. consumed—kcal. in excreta l ME = . g. feed consumed
may reflect greater fat and protein metabolism. Consumption and deposition of energy were greater for the higher energy diet than for the lower energy one. Since body weight and nitrogen retention were comparable for both energy levels, this would suggest more fat and less water in chicks fed the higher energy rations than in those fed the lower energy rations. This line-energy interaction was highly significant for energy consumed and deposited in the carcass (Table 4). Twentyeight percent more energy was consumed by HW birds fed the high energy ration than was consumed by those fed the lower energy ration. In the LW line the percentage increase was 19. Energy deposited in the carcass of HW birds increased with an increase in energy level of the ration whereas no change occurred in the LW line.
These results show that appetite as measured by feed consumption changed concomitantly with selection for body weight. Since feed was provided ad libitum, the birds in the HW line were afforded the opportunity for overconsumption which would cause a bias in measuring the utilization of feed. To remove this bias the paired feeding experiment was conducted. Experiment 2. Mean gains in body weight and feed efficiencies from 1 to 4 weeks of age are presented in Table 5. Gains in body weight were greater for birds in HW line than in the LW line where feed consumption in the former was restricted to that of the latter. Although the degree of significance for the difference between lines for body weight varied with the diet, all were significant at the P < .1 level. Significant differences in feed efficiency (P < .05) were found between lines
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2.8 3.4
SELECTION FOE BODY WEIGHT TABLE 5.—Gain in body weights and feed efficiencies from paired feeding, 1 to 4 weeks (Experiment Z) Effic.
Wt. (g.)
B C D E
HW
LW
Diff
HW
LW
Diff
304 356 322 311
262 252 251 252
48t 104" 71*» 601
.479 .528 .533 .547
.467 .464 .488 .494
.022 .074* .045* .053*
tp<.l. * P<.05 **P<.01
SUMMARY
Two experiments were conducted to measure appetite and feed utilization as influenced by selection for large and small body weight in chickens. The results show that selection for body weight was positively associated with the efficiency of feed utilization and appetite. This demonstrated further that changes in appetite could mask associated changes in feed utilization unless the former is controlled. REFERENCES Gyles, N. R., and J. E. Thomas, 1963. Divergent selection for eight week body weight in White Wyandottes. Poultry Sci. 42: 1273-1274.
Fowler, R. E., 1962. The efficiency of food utilization, digestibility of food stuffs and energy expenditure of mice selected for large and small body size. Genet. Res. Camb. 3 : 51-68. Lepore, P. D., 1965a. Methionine and protein requirements of lines of chickens established by growth-rate selection on a methionine deficient diet. Poultry Sci. 44: 797-803. Lepore, P. D., 1965b. Appetite and growth rate selection with a methionine deficient diet. Poultry Sci. 42: 1093-1097. Lepore, P. D., P. B. Siegel and K. W. King, 1963. Proximate and amino acid composition of eggs and chicks from growth selected lines of White Rocks. Life. Sci. 2: 584-593. Lepore, P. D., P. B. Siegel and H. S. Siegel, 1965. Nucleic acid composition of chicks and chick tissues from growth selected lines of White Rocks. Poultry Sci. 44: 126-130. Maloney, M. A., J. C. Gilbreath and R. D. Morrison, 1963. Two-way selection for body weight in chickens. Oklahoma Agr. Expt. Sta. Tech. Bull. T-99. Schnetzler, E. E., 1936. Inheritance of rate of growth in Barred Plymouth Rocks. Poultry Sci. 15: 369-376. Siegel, P. B., 1962. Selection for body weight at eight weeks of age. 1. Short term response and heritabilities. Poultry Sci. 4 1 : 954-962. Siegel, P. B., 1963. Selection for body weight at eight weeks of age. 2. Correlated responses of feathering, body weights, and reproductive characteristics. Poultry Sci. 42: 896-905. Siegel, P. B., and E. L. Wisman, 1962. Protein and energy requirements of chickens selected for high and low body weight. Poultry Sci. 4 1 : 1225-1232. Wisman, E. L., and P. B. Siegel, 1963. Further studies on protein and energy requirements of chicks selected for high and low body weights. Poultry Sci. 42: 541-543. Yoshida, M., S. Hizukuro, H. Hoshii and H. Morimoto, 1962. Effect of dietary protein and energy levels on the growth rate, feed efficiency and carcass composition of chicks. Agric. Biol. Chem. 26 : 640-646.
FEBRUARY 9-12. FACT FINDING CONFERENCE, INSTITUTE OF AMERICAN POULTRY INDUSTRIES, MUNICIPAL AUDITORIUM, KANSAS CITY APRIL 10-12. THE 27TH ANNUAL MEETING OF THE POULTRY AND EGG NATIONAL BOARD, PICK-CONGRESS HOTEL, CHICAGO
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fed diets C, D, and E with the birds in the HW line being more efficient than those in the LW line. Lepore et al. (1963) observed that the embryos in the HW line utilized certain amino acids more efficiently than the embryos in the LW line. The results obtained here demonstrate that selection for body weight was positively associated with appetite and efficiency of feed utilization. Determination of the efficiency of utilization of feed is difficult unless appetite is somehow controlled.
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