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A Negative Genetic Correlation Between Bursa Weight at Hatching and Post-hatching Body Growth of Chickens
FAT ABSORPTION
justify the use of the germ-free chicken for studies on the mechanism of fat absorption. SUMMARY
REFERENCES Bloch, K., P. Baronowsky, H. Goldfine, W. J. Lennarz, R. Light, A. T. Norris and G. Scheuerbrandt, 1961. Biosynthsis and metabolism of unsaturated fatty acids. Federation Proc. 20: 921-927. Brisson, G. J., 1956. On the routine determination of chromic oxide in feces. Canadian J. Agri. Sci. 36:210-211.
Edwards, H. M., Jr., 1964. The influence of breed and/or strain on the fatty acid composi.ion of egg lipids. Poultry Sci. 43: 751-754. Edwards, H. M., Jr., and F. M. Boyd, 1963a. The effect of microbial contamination on the requirement of chicks for certain nutrients. Poultry Sci. 42 : 235-240. Edwards, H. M., Jr., and F. M. Boyd, 1963b. Effect of germ-free environment on CA4' metabolism. Poultry Sci. 42: 1030-1031. Folch, J., M. Lees, and G. H. Sloan-Stanley, 1957. A simple method for the isolation and purification of total lipids from animal tissues. J. Biol. Chem. 226:497-509. Luckey, T. D., 1963. Germfree Life and Gnotobiology. Academic Press, N.Y. Renner, R., and F. W. Hill, 1961. Factors affecting the absorbability of saturated fatty acids in the chick. J. Nutrition, 74: 254-258. Young, R. J., and R. L. Garrett, 1963. Effect of oleic and linoleic acids on the absorption of saturated fatty acids in the chick. J. Nutrition, 8 1 : 321-329. Young, R. J., R. L. Garrett and M. Griffith, 1963. Factors affecting the absorbability of fatty acid mixtures high in saturated fatty acids. Poultry Sci. 42: 1146-1154.
A Negative Genetic Correlation Between Bursa Weight at Hatching and Post-hatching Body Growth of Chickens F. V. MUIR AND R. G. JAAP Ohio Agricultural Research and Development Center, Columbus, Ohio 43210 (Received for publication March 27, 1967)
W
EIGHT of the bursa of Fabricius and body weight of the baby chick are positively correlated phenotypically, (Hammond and Bird, 1942). Jaap (1960) reported that this correlation was 0.47 and 0.79 at hatching and at eleven days of age, respectively. Early body growth is accompanied by rapid hypertrophy of the bursa (Glick, 1956). Glick (19S6) had reported that the phenotypic correlations between body weight and bursa weight reached a peak of 0.76 at 4& weeks in White Leghorns and 0.92 at 6 weeks in Rhode Is-
land Reds. Therefore, a negative genetic correlation between bursa weight at hatching and post-hatching body growth was unsuspected. The bursa is larger at hatching in the Leghorn baby chick than either the Rhode Island Red (Glick, 1956) or the broilertype chick (Jaap, 1958) which attained larger adult body size. Since the Leghorn appears to be particularly adapted to resist disease as well as stress conditions (Hutt, 1958), the suggestion was made that part of this advantage of the smaller-bodied
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The germ-free chick retained greater amounts of palmitic and stearic acid than chicks in conventional environments. This difference in absorption was apparent whether stearic acid was present at a relatively high level in the diet (1.19%) or low level (0.18%). The environment did not appear to influence the chickens' absorption of oleic acid or linoleic acid.
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F. V. MUIR AND R. G. JAAP
Leghorn might be attributable to the larger bursa size at hatching (Jaap, 1958). The results to be presented indicate that the larger bursa in the Leghorn than in chicks of larger-bodied breeds may be due to a negative genetic correlation between chick bursa weight and adult body weight. MATERIALS AND METHODS
The original data pertaining to body weight were collected from 350 pullets of each BLS and BLC strains. The birds were reared together until 21 weeks of age, at
RESULTS AND DISCUSSION
The data in Table 1 include the average bursa weights of 100 BLS and 100 BLC chicks killed at hatching to assay the difference between progeny from the third generation of parents. Three generations of selection have increased the size of the bursa in the BLS strain by 33 mg., a 54% increase. The body weights presented in Table 1 were from 350 pullets of each strain, BLC and BLS, randomized in laying cages. These non-selected pullets were produced from the third generation parents. At 30 weeks of age the correlated response was sufficient to decrease body weight approximately 10% which persisted to body maturity (60 weeks). The 10% reduction in body weight was statistically highly significant (P < 0.01). In order to find the age at which the cor-
Downloaded from http://ps.oxfordjournals.org/ at Pennsylvania State University on April 16, 2015
The negative genetic correlation between body growth and bursa size at hatching was first discovered during experiments designed to test whether a genetic change in bursa weight had any measurable phenotypic effects during the post-hatching period. The strains used for this purpose arose from a common base population formed from the F 2 of reciprocal crosses between a large bursa strain B (Goodman and Jaap, 1960) and the North Central Regional (Cornell) Randombred Leghorn described by King et al. (1959). The control strain (BLC) was maintained by randombreeding from 40 paired matings per generation. The other strain (BLS), from the same base source, was selected for large bursa weight at hatching. BLS was reproduced with 60 paired matings per generation. These 60 dams and 60 sires were selected from the superior 15 to 20 full-sib families assayed by 5 chicks per family. Three to five progeny of each sex from each selected family were used for breeders in the next generation. The larger breeding unit for BLS was used to allow selection of the superior third of the families and to retain a sufficient number of families to maintain a low rate of inbreeding per generation. After three generations of selection, comparable bursa weights at hatching were 94 mg. for the selected strain BLS and 61 mg. for the BLC randombred control.
which time they were randomly assigned to cages for performance records during a laying period from the 21st to the 75th week of age. Additional evidence for estimating the genetic correlation between bursa weight at hatching and post-hatching growth has been obtained from two sources: (1) from comparisons of bursa weights at hatching of chicks from two broiler-type strains, AG1 and AG, described by Jaap (1963); and (2) from the effect of a sex-linked body dwarfing gene, dw, (Hutt, 1959) measured in two populations of chicks provided by hatching eggs supplied by a commercial breeding firm. It should be emphasized that throughout this report the phenotypic correlation between bursa and chick weight at hatching has been removed; either by using chicks having the same average weight or by using regression to adjust for a constant body weight in lots being compared. Chick bursa weights refer to weights of the bursa at a constant body weight.
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BURSA AND GROWTH TABLE 1.—Average bursa weight at hatching and body weight at 30, 48, 60 and 69 weeks of age and their standard errors for the BLS and BLC strains Body weight of females (gm.) Strain
BLS BLC Difference (BLS-BLC)
Bursa weight hatching
Week of age 30
48
60
69
94mg. + 3.53 61 mg. + 3.04
2,229+14.8 2,456+18.2
2,438 + 25.2 2,733 + 22.1
2,561 + 23.7 2,828 + 29.9
2,547 + 23.2 2,783 + 38.2
33**
-227**
-295**
-276**
-236**
related growth suppression occurred, 165 females of each strain on the test (Table 1) were artificially inseminated with pooled semen from sires used to produce the next generation of BLS and BLC. The data on growth of their chicks from 4 to 12 weeks of age are given in Table 2. Although growth rate of BLS was slightly depressed at 4, 6 and 8 weeks, this difference was not statistically significant until 10 and 12 weeks of age in males and females, respectively. It would appear that the correlated body weight suppression may be greater from 12 to 30 weeks than from hatching to 12 weeks and more a restriction of size-tobe-attained than an early growth suppression. Genetic gain in rapidity of growth to 8 weeks of age, however, does suppress
weight of the bursa of Fabricius in the baby chick. This conclusion is based on the data presented in Table 3. The first column of data in this table gives the comparable eight-week body weights obtained from a sample of 80 bursectomized chicks of each strain. Gain in eight-week weight of AG bursectomized chickens was slightly in excess of 16% above that of AG1. The second column gives the comparable eight-week body weights of non-bursectomized chickens. Eight-week body weight selection for 7 generations increased the weight of AG about 24% above that of its randombred control, AG1. Both groups, the bursectomized and non-bursectomized, were obtained from the same sample of pullets. However, the samples of chicks which were bursectomized were obtained from young
TABLE 2.—Growth rate comparison and their standard errors of BLS and BLC Age (wks.) 4 6 8 10 12
Body weight (gm.) Sex M F M F M F M F M F
BLS
BLC
304+ 4.4(116)' 277+ 4.1(107) 540+ 8.0(116) 468+ 7.1(107) 1,076+14.9(116) 872 + 12.0(107) 1,176+17.0(116) 962 + 13.1 (107) 1,548 + 16.8(116) 1,153 + 14.7(107)
313+ 4.8(104) 286+ 4.0(118) 549+ 9.7(104) 486+ 7.1(118) 1,090+16.0(104) 894+11.8(118) 1,235 + 17.4(104) 990+10.8(118) 1,639 + 18.2(104) 1,199+13.9(118)
* P<0.05. ** P<0.01. 1 Indicates the number of birds weighted at each age.
Difference (BLS-BLC) - 9 - 9 - 9 -18 -14 -22 -59* -28 _91** -46*
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**P<0.01.
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F. V. MUIE AND R. G. JAAP
TABLE 3.—Bursa weight at hatching compared with
bursectomized and non-bursectomized 8-week body weight and their standard errors for a growth selected strain Body weight at 8 weeks (gm.) Strain
N
Bursectomized AG AG1 Difference (AG-AG1)
1,228+31.2 1,062 + 25.1 116**
Bursectomized
1,434.6+20.6 1,157.7+17.9 276.9**
Bursa weight at hatching 32.54+0.75 38.96±1.06 -6.43**
**P<0.01.
TABLE 4.—Average body and bursa weight at hatching
and their standard errors for chicks hemizygous or heterozygous normal and hemizygous or homozygous dwarf Phenotype Normal Dwarf Difference (Normal-Dwarf) *P<0.05. "P<0.01.
-K- , l-'i „ cmcks 138 132
Body weight at hatching
Bursa weight at hatching
(gm)
(mgJ
29.5 + 0.25 30.2 + 0.23
35.87 + 0.73 39.17 + 0.75
-0.7*
-3.3**
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pullets 4 weeks before the non-bursectomized chicks, and age of dam probably was a factor (Temple and Jaap, 1961). The remainder of the difference between the bursectomized and non-bursectomized groups could be attributed to differences in egg weight. When growth is suppressed environmentally, the suppression is greater on the more rapidly growing strain. Therefore, the smaller difference between AG and AG1 in the bursectomized chickens might be attributable to environmental suppression of growth rather than lack of a bursa or slow recovery from the operation. Bursa weights at hatching data in Table 3 were obtained by surgical bursectomy of the birds used to measure bursectomized body weight at 8 weeks (Column 1 of Table 3). The data in Table 3 indicate that the absence of the bursa has a small effect on the relative growth rate of the strains after hatching. If there is any direct physiological effect of the bursa on post-hatching body growth, it probably has been initiated by hatching time, or due to cells from the bursa colonizing other tissue prior to hatching (Jaffe and Fechheimer, 1966). The third source of evidence for a genetic correlation between bursa weight at hatching and post-hatching body growth involves a major sex-linked dwarfing gene, dw. According to Hutt (1959), this gene reduces the adult size of hemizygous females by 26-32%. It has little, if any, effect on adult weight of heterozygous males while the homozygous males, dw dw,
are reduced 38-46% in mature body weight. Although the dw gene has been found in several lines, the commercial company had transferred dw to a highly inbred, normalbodied, Leghorn-type parental line by a series of backcrosses. Thus, two strains were available, differing primarily in the dw region of the sex chromosome. To test whether the dw gene also affected bursa weight at hatching, samples of the same dw population were mated to normal and dwarf males. This provided 132 phenotypically normal and 138 dwarf chicks from eggs of the same size laid by dams of the same age. Average bursa and chick weights are given in Table 4. The slightly greater body weight of dwarf than normal chicks was significent. Dwarf chicks which were either hemizygous (females) or homozygous dw dw (males) had bursas which averaged 3.3 mg, larger than those of hemizygous Dw, or heterozygous, Dw dw, normals. This increase of 9.2% in bursa weight attributable to the dw allele was highly significant. If the only difference in these populations may be attributable to that portion of the Z-chromosome bearing the dw locus, a pleiotopic effect of the alleles at the dw locus is indicated for both bursa weight at hatching and mature body weight. The relatively large effect of dw on mature body weight as contrasted to a much smaller effect on chick bursa weight would indicate that other genes are affecting bursa weight in the newly-hatched chicks because small-
BURSA AND GROWTH
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er changes in adult size occur with much the first few weeks after hatching. This relarger changes in chick bursa size. duction can be partially restored by graftInsufficient evidence is available to indicate ing a piece of bursa into bursectomized whether all genes which affect body size chicks. (St. Pierre and Ackerman, 1965; also affect weight of the baby chick's bursa. Jankovic and Leskowitz, 1965). The role There has been no evidence in research of the bursa in antibody production has rereports that the bursa has any physiolog- cently been reviewed by Jaffe (1966). ical effect to depress body size or vice Sadler and Glick (1962) obtained higher versa. The positive phenotypic correlation antibody titers in birds with larger bursas. between bursa and body growth during the Claflin et al. (1966) reported a correlation first few weeks after hatching might indi- of 0.59 between log2 antibody titer on the cate that the size of the bursa could be second day following immunization and log beneficial rather than detrimental to body bursa weight from 6000 mg. down to about growth. However, the growth of bursecto- 200 mg. In contrast, Jaffe and Jaap (1966) mized chicks is suppressed only slightly were unable to demonstrate differences in below that of normal chicks during the first mortality during a four-week period followfew weeks after hatching (Glick, 1964). ing Salmonella pullorum infection between This depression in body weight could be strains of chicks differing greatly in bursa the result of the surgery to remove the weight at hatching. Likewise, there was no bursa. significant difference in antibody producThe bursa appears to be associated with tion at 21 days of age due to Salmonella the adrenal stress complex (Newcomer and typhimurium infection between the B strain Connally, 1960; Perek and Eilat, 1960) having a bursa weight of 107 mg. and a even though the bursa has not been proven randombred Leghorn strain with a 51 mg. to aid or depress the bird's ability to resist bursa weight at hatching. The relative imstressors. At 2, 4, 6, 8 and 10 weeks of age, portance of the size of bursa at hatching Muir and Brown (1965) were unable to and antibody production or disease resisdetect any differences in the amount of cir- tance in the early growing period of the culating glucocorticosteroids attributable to chicken is not clear at this time. strains differing in size of the bursa at SUMMARY hatching. Challey (1962) found that bursectomized chickens responded in a similar Increasing the weight of the bursa of manner to control birds with respect to Fabricius at hatching about 50% through adrenal size, adrenal ascorbic acid and selective breeding depressed post-hatching adrenal corticosterone when infected with growth rate. At ten weeks of age this corcecal coccidiosis. The involvement of the related decrease in body size was approxibursa in stress would indicate that the mately 5%. By 30 weeks of age, the body bursa assists rather than restricts body weight of the non-selected females was regrowth, particularly during unfavorable duced about 10% and no further reduction environmental conditions. occurred during the remainder of the growThe bursa plays a role in antibody pro- ing period. duction in the young chick and its removal, Selection for rapidity of growth to eight either surgically (Glick et al., 1956; Chang weeks of age resulted in a correlated weight et al., 1957) or hormonally (Meyer et al., suppression of the bursa of Fabricius in the 1959; Glick and Sadler, 1961; Glick, chicks at hatching. The sex-linked dwarfing 1961), reduces antibody production during gene, dw, which reduces adult weight 26 to
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F. V. MUIR AND R. G. JAAP
REFERENCES Challey, J. R., 1962. The role of the bursa of Fabricius in adrenal response and mortality due to Eimeria tenella infection in the chicken. J. Parasitol. 48:352-357. Chang, T. S., M. S. Rheins and A. R. Winter, 1957. The significance of the bursa of Fabricius in antibody production in chickens. 1. Age of chickens. Poultry Sci. 36: 735-738. Claflin, A. J., O. Smithies and R. K. Meyer, 1966. Antibody responses in bursa-deficient chickens. J. Immunol. 97: 693-699. Glick, B., 1956. Normal growth of the bursa of Fabricius in chickens. Poultry Sci. 35: 843-851. Glick, B., 1964. The bursa of Fabricius and the development of immunologic competence in: The Thymus in Immunobiology. Edited by R. A. Good and Ann R. Gabrielson. Hoefer Medical Div., Harper and Row, N. Y., pp. 343-358. Glick, B., T. S. Chang and R. G. Jaap, 1956. The bursa of Fabricius and antibody production. Poultry Sci. 35: 224-225. Glick, B., and C. R. Sadler, 1961. The elimination of the bursa of Fabricius and reduction of antibody production in birds from eggs dipped in hormone solution. Poultry Sci. 40: 185-189. Goodman, B. L., and R. G. Jaap, 1960. Improving accuracy of heritability estimates from diallel and triallel matings in poultry. 2. Weight of spleen and bursa of Fabricius in a randombred population. Poultry Sci. 39: 944-949. Hammond, J. C , and H. R. Bird, 1942. Size of thymus and bursa Fabricius in relation to rate of growth in chicks. Poultry Sci. 2 1 : 116-119. Hutt, F. B., 1958. The Efficient Leghorn in Genetic Resistance to Disease in Domestic Animals. pp. 139-140, Ithaca, N.Y. Hutt, F. B., 1959. Sex-linked dwarfism in the fowl. J. Heredity, 50: 209-221.
Jaap, R. G., 1958. Large bursa Fabricii in Leghorn-type baby chickens. Poultry Sci. 37: 1462-1464. Jaap, R. G., 1960. Heritabilities, gene interaction and correlations for growth of glands associated with antibody formation in the young chicken. Poultry Sci. 39: 557-569. Jaap, R. G., 1963. Selection for rapid growth rate in chickens. Poultry Sci. 42: 1393-1397. Jaffe, W. P., 1966. The role of the bursa of Fabricius and the thymus in chickens. World's Poultry Sci. J. 22 : 25-30. Jaffe, W. P., and N. S. Fechheimer, 1966. Cell transport and the bursa of Fabricius. Nature, 212:92. Jaffe, W. P., and R. G. Jaap, 1966. A lack of effect of bursa size on disease resistance and antibody production. Poultry Sci. 45: 157-159. Jankovic, B. D., and S. Leskowitz, 1965. Restoration of antibody producing capacity in bursectomized chickens by bursal grafts in millipore chambers. Proc. Soc. Exptl. Biol. Med. 118: 1164. King, S. C , J. R. Carson and D. P. Doolittle, 1959. The Connecticut and Cornell Randombred populations of chickens. World's Poultry Sci. J. 15: 139-159. Meyer, R. K., M. A. Rao and R. L. Aspinall, 1959. Inhibition of the development of the bursa of Fabricius in the embryos of the common fowl by 19-nortestosterone. Endocrinology, 64: 890-897. Muir, F. V., and K. I. Brown, 1965. Circulating glucocorticosteroids in chickens differing in bursa weight at hatching. Poultry Sci. 44: 1401. Newcomer, W. S., and J. D. Connally, 1960. The bursa of Fabricius as an indication of chronic stress in immature chickens. Endocrinology, 67: 264-266. Perek, M., and A. Eilat, 1960. The bursa of Fabricius and adrenal ascorbic acid depletion following ACTH injection of chicks. J. Endocrinology, 20: 251-255. Sadler, C. R., and B. Glick, 1962. The relationship of the size of the bursa of Fabricius to antibody production. Poultry Sci. 4 1 : 508510. St. Pierre, R. L., and G. A. Ackerman, 1965. Bursa of Fabricius in chickens: Possible humoral factor. Science, 147: 1307-1308. Temple, R. W., and R. G. Jaap, 1961. Age of dam and response to selection for increased weight of the bursa of Fabricius in day-old chicks. Poultry Sci. 40: 1355-1359.
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32% in females and 38 to 46% in males, is associated with an increase in bursa size at hatching. Data from these three sources have demonstrated the existence of a negative genetic correlation between bursa weight at hatching and post-hatching body growth. The larger size of the bursa in smallerbodied Leghorn chicks may be attributable to this correlation and not necessarily associated with the Leghorn's superiority to resist stress and some diseases.
justify the use of the germ-free chicken for studies on the mechanism of fat absorption. SUMMARY
REFERENCES Bloch, K., P. Baronowsky, H. Goldfine, W. J. Lennarz, R. Light, A. T. Norris and G. Scheuerbrandt, 1961. Biosynthsis and metabolism of unsaturated fatty acids. Federation Proc. 20: 921-927. Brisson, G. J., 1956. On the routine determination of chromic oxide in feces. Canadian J. Agri. Sci. 36:210-211.
Edwards, H. M., Jr., 1964. The influence of breed and/or strain on the fatty acid composi.ion of egg lipids. Poultry Sci. 43: 751-754. Edwards, H. M., Jr., and F. M. Boyd, 1963a. The effect of microbial contamination on the requirement of chicks for certain nutrients. Poultry Sci. 42 : 235-240. Edwards, H. M., Jr., and F. M. Boyd, 1963b. Effect of germ-free environment on CA4' metabolism. Poultry Sci. 42: 1030-1031. Folch, J., M. Lees, and G. H. Sloan-Stanley, 1957. A simple method for the isolation and purification of total lipids from animal tissues. J. Biol. Chem. 226:497-509. Luckey, T. D., 1963. Germfree Life and Gnotobiology. Academic Press, N.Y. Renner, R., and F. W. Hill, 1961. Factors affecting the absorbability of saturated fatty acids in the chick. J. Nutrition, 74: 254-258. Young, R. J., and R. L. Garrett, 1963. Effect of oleic and linoleic acids on the absorption of saturated fatty acids in the chick. J. Nutrition, 8 1 : 321-329. Young, R. J., R. L. Garrett and M. Griffith, 1963. Factors affecting the absorbability of fatty acid mixtures high in saturated fatty acids. Poultry Sci. 42: 1146-1154.
A Negative Genetic Correlation Between Bursa Weight at Hatching and Post-hatching Body Growth of Chickens F. V. MUIR AND R. G. JAAP Ohio Agricultural Research and Development Center, Columbus, Ohio 43210 (Received for publication March 27, 1967)
W
EIGHT of the bursa of Fabricius and body weight of the baby chick are positively correlated phenotypically, (Hammond and Bird, 1942). Jaap (1960) reported that this correlation was 0.47 and 0.79 at hatching and at eleven days of age, respectively. Early body growth is accompanied by rapid hypertrophy of the bursa (Glick, 1956). Glick (19S6) had reported that the phenotypic correlations between body weight and bursa weight reached a peak of 0.76 at 4& weeks in White Leghorns and 0.92 at 6 weeks in Rhode Is-
land Reds. Therefore, a negative genetic correlation between bursa weight at hatching and post-hatching body growth was unsuspected. The bursa is larger at hatching in the Leghorn baby chick than either the Rhode Island Red (Glick, 1956) or the broilertype chick (Jaap, 1958) which attained larger adult body size. Since the Leghorn appears to be particularly adapted to resist disease as well as stress conditions (Hutt, 1958), the suggestion was made that part of this advantage of the smaller-bodied
Downloaded from http://ps.oxfordjournals.org/ at Pennsylvania State University on April 16, 2015
The germ-free chick retained greater amounts of palmitic and stearic acid than chicks in conventional environments. This difference in absorption was apparent whether stearic acid was present at a relatively high level in the diet (1.19%) or low level (0.18%). The environment did not appear to influence the chickens' absorption of oleic acid or linoleic acid.
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F. V. MUIR AND R. G. JAAP
Leghorn might be attributable to the larger bursa size at hatching (Jaap, 1958). The results to be presented indicate that the larger bursa in the Leghorn than in chicks of larger-bodied breeds may be due to a negative genetic correlation between chick bursa weight and adult body weight. MATERIALS AND METHODS
The original data pertaining to body weight were collected from 350 pullets of each BLS and BLC strains. The birds were reared together until 21 weeks of age, at
RESULTS AND DISCUSSION
The data in Table 1 include the average bursa weights of 100 BLS and 100 BLC chicks killed at hatching to assay the difference between progeny from the third generation of parents. Three generations of selection have increased the size of the bursa in the BLS strain by 33 mg., a 54% increase. The body weights presented in Table 1 were from 350 pullets of each strain, BLC and BLS, randomized in laying cages. These non-selected pullets were produced from the third generation parents. At 30 weeks of age the correlated response was sufficient to decrease body weight approximately 10% which persisted to body maturity (60 weeks). The 10% reduction in body weight was statistically highly significant (P < 0.01). In order to find the age at which the cor-
Downloaded from http://ps.oxfordjournals.org/ at Pennsylvania State University on April 16, 2015
The negative genetic correlation between body growth and bursa size at hatching was first discovered during experiments designed to test whether a genetic change in bursa weight had any measurable phenotypic effects during the post-hatching period. The strains used for this purpose arose from a common base population formed from the F 2 of reciprocal crosses between a large bursa strain B (Goodman and Jaap, 1960) and the North Central Regional (Cornell) Randombred Leghorn described by King et al. (1959). The control strain (BLC) was maintained by randombreeding from 40 paired matings per generation. The other strain (BLS), from the same base source, was selected for large bursa weight at hatching. BLS was reproduced with 60 paired matings per generation. These 60 dams and 60 sires were selected from the superior 15 to 20 full-sib families assayed by 5 chicks per family. Three to five progeny of each sex from each selected family were used for breeders in the next generation. The larger breeding unit for BLS was used to allow selection of the superior third of the families and to retain a sufficient number of families to maintain a low rate of inbreeding per generation. After three generations of selection, comparable bursa weights at hatching were 94 mg. for the selected strain BLS and 61 mg. for the BLC randombred control.
which time they were randomly assigned to cages for performance records during a laying period from the 21st to the 75th week of age. Additional evidence for estimating the genetic correlation between bursa weight at hatching and post-hatching growth has been obtained from two sources: (1) from comparisons of bursa weights at hatching of chicks from two broiler-type strains, AG1 and AG, described by Jaap (1963); and (2) from the effect of a sex-linked body dwarfing gene, dw, (Hutt, 1959) measured in two populations of chicks provided by hatching eggs supplied by a commercial breeding firm. It should be emphasized that throughout this report the phenotypic correlation between bursa and chick weight at hatching has been removed; either by using chicks having the same average weight or by using regression to adjust for a constant body weight in lots being compared. Chick bursa weights refer to weights of the bursa at a constant body weight.
1485
BURSA AND GROWTH TABLE 1.—Average bursa weight at hatching and body weight at 30, 48, 60 and 69 weeks of age and their standard errors for the BLS and BLC strains Body weight of females (gm.) Strain
BLS BLC Difference (BLS-BLC)
Bursa weight hatching
Week of age 30
48
60
69
94mg. + 3.53 61 mg. + 3.04
2,229+14.8 2,456+18.2
2,438 + 25.2 2,733 + 22.1
2,561 + 23.7 2,828 + 29.9
2,547 + 23.2 2,783 + 38.2
33**
-227**
-295**
-276**
-236**
related growth suppression occurred, 165 females of each strain on the test (Table 1) were artificially inseminated with pooled semen from sires used to produce the next generation of BLS and BLC. The data on growth of their chicks from 4 to 12 weeks of age are given in Table 2. Although growth rate of BLS was slightly depressed at 4, 6 and 8 weeks, this difference was not statistically significant until 10 and 12 weeks of age in males and females, respectively. It would appear that the correlated body weight suppression may be greater from 12 to 30 weeks than from hatching to 12 weeks and more a restriction of size-tobe-attained than an early growth suppression. Genetic gain in rapidity of growth to 8 weeks of age, however, does suppress
weight of the bursa of Fabricius in the baby chick. This conclusion is based on the data presented in Table 3. The first column of data in this table gives the comparable eight-week body weights obtained from a sample of 80 bursectomized chicks of each strain. Gain in eight-week weight of AG bursectomized chickens was slightly in excess of 16% above that of AG1. The second column gives the comparable eight-week body weights of non-bursectomized chickens. Eight-week body weight selection for 7 generations increased the weight of AG about 24% above that of its randombred control, AG1. Both groups, the bursectomized and non-bursectomized, were obtained from the same sample of pullets. However, the samples of chicks which were bursectomized were obtained from young
TABLE 2.—Growth rate comparison and their standard errors of BLS and BLC Age (wks.) 4 6 8 10 12
Body weight (gm.) Sex M F M F M F M F M F
BLS
BLC
304+ 4.4(116)' 277+ 4.1(107) 540+ 8.0(116) 468+ 7.1(107) 1,076+14.9(116) 872 + 12.0(107) 1,176+17.0(116) 962 + 13.1 (107) 1,548 + 16.8(116) 1,153 + 14.7(107)
313+ 4.8(104) 286+ 4.0(118) 549+ 9.7(104) 486+ 7.1(118) 1,090+16.0(104) 894+11.8(118) 1,235 + 17.4(104) 990+10.8(118) 1,639 + 18.2(104) 1,199+13.9(118)
* P<0.05. ** P<0.01. 1 Indicates the number of birds weighted at each age.
Difference (BLS-BLC) - 9 - 9 - 9 -18 -14 -22 -59* -28 _91** -46*
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**P<0.01.
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TABLE 3.—Bursa weight at hatching compared with
bursectomized and non-bursectomized 8-week body weight and their standard errors for a growth selected strain Body weight at 8 weeks (gm.) Strain
N
Bursectomized AG AG1 Difference (AG-AG1)
1,228+31.2 1,062 + 25.1 116**
Bursectomized
1,434.6+20.6 1,157.7+17.9 276.9**
Bursa weight at hatching 32.54+0.75 38.96±1.06 -6.43**
**P<0.01.
TABLE 4.—Average body and bursa weight at hatching
and their standard errors for chicks hemizygous or heterozygous normal and hemizygous or homozygous dwarf Phenotype Normal Dwarf Difference (Normal-Dwarf) *P<0.05. "P<0.01.
-K- , l-'i „ cmcks 138 132
Body weight at hatching
Bursa weight at hatching
(gm)
(mgJ
29.5 + 0.25 30.2 + 0.23
35.87 + 0.73 39.17 + 0.75
-0.7*
-3.3**
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pullets 4 weeks before the non-bursectomized chicks, and age of dam probably was a factor (Temple and Jaap, 1961). The remainder of the difference between the bursectomized and non-bursectomized groups could be attributed to differences in egg weight. When growth is suppressed environmentally, the suppression is greater on the more rapidly growing strain. Therefore, the smaller difference between AG and AG1 in the bursectomized chickens might be attributable to environmental suppression of growth rather than lack of a bursa or slow recovery from the operation. Bursa weights at hatching data in Table 3 were obtained by surgical bursectomy of the birds used to measure bursectomized body weight at 8 weeks (Column 1 of Table 3). The data in Table 3 indicate that the absence of the bursa has a small effect on the relative growth rate of the strains after hatching. If there is any direct physiological effect of the bursa on post-hatching body growth, it probably has been initiated by hatching time, or due to cells from the bursa colonizing other tissue prior to hatching (Jaffe and Fechheimer, 1966). The third source of evidence for a genetic correlation between bursa weight at hatching and post-hatching body growth involves a major sex-linked dwarfing gene, dw. According to Hutt (1959), this gene reduces the adult size of hemizygous females by 26-32%. It has little, if any, effect on adult weight of heterozygous males while the homozygous males, dw dw,
are reduced 38-46% in mature body weight. Although the dw gene has been found in several lines, the commercial company had transferred dw to a highly inbred, normalbodied, Leghorn-type parental line by a series of backcrosses. Thus, two strains were available, differing primarily in the dw region of the sex chromosome. To test whether the dw gene also affected bursa weight at hatching, samples of the same dw population were mated to normal and dwarf males. This provided 132 phenotypically normal and 138 dwarf chicks from eggs of the same size laid by dams of the same age. Average bursa and chick weights are given in Table 4. The slightly greater body weight of dwarf than normal chicks was significent. Dwarf chicks which were either hemizygous (females) or homozygous dw dw (males) had bursas which averaged 3.3 mg, larger than those of hemizygous Dw, or heterozygous, Dw dw, normals. This increase of 9.2% in bursa weight attributable to the dw allele was highly significant. If the only difference in these populations may be attributable to that portion of the Z-chromosome bearing the dw locus, a pleiotopic effect of the alleles at the dw locus is indicated for both bursa weight at hatching and mature body weight. The relatively large effect of dw on mature body weight as contrasted to a much smaller effect on chick bursa weight would indicate that other genes are affecting bursa weight in the newly-hatched chicks because small-
BURSA AND GROWTH
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er changes in adult size occur with much the first few weeks after hatching. This relarger changes in chick bursa size. duction can be partially restored by graftInsufficient evidence is available to indicate ing a piece of bursa into bursectomized whether all genes which affect body size chicks. (St. Pierre and Ackerman, 1965; also affect weight of the baby chick's bursa. Jankovic and Leskowitz, 1965). The role There has been no evidence in research of the bursa in antibody production has rereports that the bursa has any physiolog- cently been reviewed by Jaffe (1966). ical effect to depress body size or vice Sadler and Glick (1962) obtained higher versa. The positive phenotypic correlation antibody titers in birds with larger bursas. between bursa and body growth during the Claflin et al. (1966) reported a correlation first few weeks after hatching might indi- of 0.59 between log2 antibody titer on the cate that the size of the bursa could be second day following immunization and log beneficial rather than detrimental to body bursa weight from 6000 mg. down to about growth. However, the growth of bursecto- 200 mg. In contrast, Jaffe and Jaap (1966) mized chicks is suppressed only slightly were unable to demonstrate differences in below that of normal chicks during the first mortality during a four-week period followfew weeks after hatching (Glick, 1964). ing Salmonella pullorum infection between This depression in body weight could be strains of chicks differing greatly in bursa the result of the surgery to remove the weight at hatching. Likewise, there was no bursa. significant difference in antibody producThe bursa appears to be associated with tion at 21 days of age due to Salmonella the adrenal stress complex (Newcomer and typhimurium infection between the B strain Connally, 1960; Perek and Eilat, 1960) having a bursa weight of 107 mg. and a even though the bursa has not been proven randombred Leghorn strain with a 51 mg. to aid or depress the bird's ability to resist bursa weight at hatching. The relative imstressors. At 2, 4, 6, 8 and 10 weeks of age, portance of the size of bursa at hatching Muir and Brown (1965) were unable to and antibody production or disease resisdetect any differences in the amount of cir- tance in the early growing period of the culating glucocorticosteroids attributable to chicken is not clear at this time. strains differing in size of the bursa at SUMMARY hatching. Challey (1962) found that bursectomized chickens responded in a similar Increasing the weight of the bursa of manner to control birds with respect to Fabricius at hatching about 50% through adrenal size, adrenal ascorbic acid and selective breeding depressed post-hatching adrenal corticosterone when infected with growth rate. At ten weeks of age this corcecal coccidiosis. The involvement of the related decrease in body size was approxibursa in stress would indicate that the mately 5%. By 30 weeks of age, the body bursa assists rather than restricts body weight of the non-selected females was regrowth, particularly during unfavorable duced about 10% and no further reduction environmental conditions. occurred during the remainder of the growThe bursa plays a role in antibody pro- ing period. duction in the young chick and its removal, Selection for rapidity of growth to eight either surgically (Glick et al., 1956; Chang weeks of age resulted in a correlated weight et al., 1957) or hormonally (Meyer et al., suppression of the bursa of Fabricius in the 1959; Glick and Sadler, 1961; Glick, chicks at hatching. The sex-linked dwarfing 1961), reduces antibody production during gene, dw, which reduces adult weight 26 to
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F. V. MUIR AND R. G. JAAP
REFERENCES Challey, J. R., 1962. The role of the bursa of Fabricius in adrenal response and mortality due to Eimeria tenella infection in the chicken. J. Parasitol. 48:352-357. Chang, T. S., M. S. Rheins and A. R. Winter, 1957. The significance of the bursa of Fabricius in antibody production in chickens. 1. Age of chickens. Poultry Sci. 36: 735-738. Claflin, A. J., O. Smithies and R. K. Meyer, 1966. Antibody responses in bursa-deficient chickens. J. Immunol. 97: 693-699. Glick, B., 1956. Normal growth of the bursa of Fabricius in chickens. Poultry Sci. 35: 843-851. Glick, B., 1964. The bursa of Fabricius and the development of immunologic competence in: The Thymus in Immunobiology. Edited by R. A. Good and Ann R. Gabrielson. Hoefer Medical Div., Harper and Row, N. Y., pp. 343-358. Glick, B., T. S. Chang and R. G. Jaap, 1956. The bursa of Fabricius and antibody production. Poultry Sci. 35: 224-225. Glick, B., and C. R. Sadler, 1961. The elimination of the bursa of Fabricius and reduction of antibody production in birds from eggs dipped in hormone solution. Poultry Sci. 40: 185-189. Goodman, B. L., and R. G. Jaap, 1960. Improving accuracy of heritability estimates from diallel and triallel matings in poultry. 2. Weight of spleen and bursa of Fabricius in a randombred population. Poultry Sci. 39: 944-949. Hammond, J. C , and H. R. Bird, 1942. Size of thymus and bursa Fabricius in relation to rate of growth in chicks. Poultry Sci. 2 1 : 116-119. Hutt, F. B., 1958. The Efficient Leghorn in Genetic Resistance to Disease in Domestic Animals. pp. 139-140, Ithaca, N.Y. Hutt, F. B., 1959. Sex-linked dwarfism in the fowl. J. Heredity, 50: 209-221.
Jaap, R. G., 1958. Large bursa Fabricii in Leghorn-type baby chickens. Poultry Sci. 37: 1462-1464. Jaap, R. G., 1960. Heritabilities, gene interaction and correlations for growth of glands associated with antibody formation in the young chicken. Poultry Sci. 39: 557-569. Jaap, R. G., 1963. Selection for rapid growth rate in chickens. Poultry Sci. 42: 1393-1397. Jaffe, W. P., 1966. The role of the bursa of Fabricius and the thymus in chickens. World's Poultry Sci. J. 22 : 25-30. Jaffe, W. P., and N. S. Fechheimer, 1966. Cell transport and the bursa of Fabricius. Nature, 212:92. Jaffe, W. P., and R. G. Jaap, 1966. A lack of effect of bursa size on disease resistance and antibody production. Poultry Sci. 45: 157-159. Jankovic, B. D., and S. Leskowitz, 1965. Restoration of antibody producing capacity in bursectomized chickens by bursal grafts in millipore chambers. Proc. Soc. Exptl. Biol. Med. 118: 1164. King, S. C , J. R. Carson and D. P. Doolittle, 1959. The Connecticut and Cornell Randombred populations of chickens. World's Poultry Sci. J. 15: 139-159. Meyer, R. K., M. A. Rao and R. L. Aspinall, 1959. Inhibition of the development of the bursa of Fabricius in the embryos of the common fowl by 19-nortestosterone. Endocrinology, 64: 890-897. Muir, F. V., and K. I. Brown, 1965. Circulating glucocorticosteroids in chickens differing in bursa weight at hatching. Poultry Sci. 44: 1401. Newcomer, W. S., and J. D. Connally, 1960. The bursa of Fabricius as an indication of chronic stress in immature chickens. Endocrinology, 67: 264-266. Perek, M., and A. Eilat, 1960. The bursa of Fabricius and adrenal ascorbic acid depletion following ACTH injection of chicks. J. Endocrinology, 20: 251-255. Sadler, C. R., and B. Glick, 1962. The relationship of the size of the bursa of Fabricius to antibody production. Poultry Sci. 4 1 : 508510. St. Pierre, R. L., and G. A. Ackerman, 1965. Bursa of Fabricius in chickens: Possible humoral factor. Science, 147: 1307-1308. Temple, R. W., and R. G. Jaap, 1961. Age of dam and response to selection for increased weight of the bursa of Fabricius in day-old chicks. Poultry Sci. 40: 1355-1359.
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32% in females and 38 to 46% in males, is associated with an increase in bursa size at hatching. Data from these three sources have demonstrated the existence of a negative genetic correlation between bursa weight at hatching and post-hatching body growth. The larger size of the bursa in smallerbodied Leghorn chicks may be attributable to this correlation and not necessarily associated with the Leghorn's superiority to resist stress and some diseases.