Meat Yield of Broilers of Different Breeds, Strains and Crosses

968 H. E. HATHAWAY, G. B. CHAMPAGNE, A. B. WATTS AND C. W. UPP was recovered in the gastrointestinal tract. Terramycin was present at the highest concentration; 19 percent of the dose remained in the digestive tract. Considering only the small intestine and caeca, where the majority of microgranisms are located, we note that Chloromycetin was present in very low concentrations as compared to the other antibiotics. These data suggest that the failure to obtain appreciable growth stimulation from crystalline Chloromycetin may be due to its rapid absorption from the digestive tract. The studies conducted by Luckey (1952) using germ-free chicks indicate that antibiotics stimulate growth by acting on the microflora present in the digestive tract. Since orally administered Chloromycetin is present in very small quantities, it may not have any effect on the intestinal microflora. REFERENCES Branion, H. D., and D. C. Hill, 1951. The comparative effect of antibiotics on the growth of poults. Poultry Sci. 30: 793-798. Heuser, G. H., and L. C. Norris, 1952. Some results of feeding antibiotics to chickens. Poultry Sci. 31: 857-862. Joslyn, D. A., and M. Gailbraith, 1950. A turbidimetric method for the assay of antibiotics. J. Bact. 59: 711-716. Luckey, T. D., 1952. Effect of feeding antibiotics upon the growth rate of germ-free birds. Colloquium held by Lobund Institute at the University of Notre Dame. Feedstuffs 24(25): 10. Official Food and Drug Administration Method, Federal Security Agency. 1951, pp. 141.1. Meat Yield of Broilers of Different Breeds, Strains and Crosses H. E. HATHAWAY, G. B. CHAMPAGNE,* A. B. WATTS AND C. W. UPP Department of Poultry Industry, Louisiana State University, Baton Rouge GROWTH of the broiler industry has stimulated the breeding of poultry for meat producing qualities. Consumers are interested in the amount of edible meat obtained, processors are interested in dressing and eviscerating yields and the breeders are interested in the production of a bird that satisfies both and does it efficiently. Several workers have reported dressed and eviscerated yields of broilers. In reports by Jull and Maw (1923); Lowe (1941); Jull et al. (1943); Essary et al. (1951); and Jaap et al. (1950) the dressed yields ranged from 85 to 90 percent of live and eviscerated La. : Now with J. T. Gibbons, Inc., New Orleans, (Received for publication March 3, 1953) yields varied from 65 to 75 percent of live. Reports by Brown and Bean (1952) and Broadbent and Bean (1952) give an edible yield of 48.5 percent of live for fryers and 54.7 percent for roasters. This increase in yield with increase in age and size confirms the work of McNally and Spicknall (1949). Stotts and Darrow (1953) report yields of meat from Cornish crossbreds, non-cornish crossbreds and certain purebreds. Their results are reported on the basis of drawn s and the use of "cooked-in-stockinette" technique. Cornish crossbreds gave consistently higher meat yields. The growth pattern of Cornish, using measurements on live birds was reported by Gilbreath and

MEAT YIELD OF BROILERS 969 Upp (1952). Hathaway (1952, 1953) gives additional data on meat yields. In the 1953 report birds of both sexes standardized at 2.0 lbs. were used. The objectives of this experiment were to determine the percentage yields of breast and total meat from various strains and crosses. To determine whether breed differences exist in body measurements and breast and total edible meat yield. Also to seek a single measure that would be as good a criterion as a combination of measures in predicting the meat yields of broilers at twelve weeks. MATERIALS AND METHODS Seven different breeds, strains and crosses were compared for total edible meat yield and breast meat yield at twelve weeks. Three trials were conducted involving eighteen lots with one hundred chicks per lot. The first trial extended from October 9, 1949 to February 20, 1950, the second trial from March 15, 1950 to June 7, 1950 and the third trial from November 1, 1950 to February 22, 1951. In trial 1 three non-broiler strains and three broiler lots were compared. The non-broiler stock lots were represented by Dark Cornish, White Plymouth Rocks and production s. The broiler strains tested were Crossbred A, A and B. Trial 2 consisted of the same number of lots with Crossbred B being substituted for the production s. No B females were grown in this trial. The same number of lots was used in trial 3, involving the same breeds, strains and crosses as in trial 2. B females were included in this trial. All lots were started on clean wood shavings litter which was stirred when necessary. Electric canopy hovers were used for brooding and each lot was brooded in an individual pen with the birds being confined to the houses at all times. A 24 percent protein chick starter was fed for the first two weeks and gradually changed to 20 percent protein mash at the third week. At twelve weeks, ten males and ten females were selected from each lot In trials 1 and 3 selection was made by calculating the average of males and females separately in each of the six lots. The samples selected were as close as possible to the average of each sex in each lot. In trial 2 the average s for all males and all females were calculated. Birds of each sex from each lot were selected as close as possible to the composite average of all lots for each sex. Feed was withheld overnight and the birds weighed immediately prior to being killed. They were then dressed, weighed, and cooled overnight in a dry air temperature of 40 F. Body measurements were then made on each individual bird. These measurements included the length of the keel, body depth, and breast width. The breast width was determined by averaging the keel length of each sex for each lot and a solder wire half this length was used for the measure. This wire was shaped to the bird's breast approximately one and one-half inches posterior to the anterior end of the keel. The width of that angle, the body depth and keel length were measured on a vernier caliper. In trial 1 the birds were not eviscerated before deboning. However, in trials 2 and 3 the birds were eviscerated prior to deboning. The edible meat was removed from the bones using a sharp knife. The breast meat was removed first and weighed separately from the rest of the edible meat. The legs were disjointed and the meat separated from the bones. The wings were then disjointed and deboned with only the humerus of the wing

970 H. E. HATHAWAY, G. B. CHAMPAGNE, A. B. WATTS AND C. W. UPP TABLE 1. Summary of results of trial 1 Breed Sex* (grams) N.Y. dressed as % of live Total edible as % of live Breast yield as % of live Dark Cornish 1,418 1,179 1,299 90.1 89.7 89.8 35.1 36.1 35.6 13.7 15.2 14.5 White Plymouth Rocks 1,373 1,079 1,226 89.6 89.9 89.7 33.0 31.4 32.2 12.7 13.1 12.9 B Strain A Strain Production Strain s Crossbred A 1,900 1,426 1,663 1,882 1,414 1,648 1,501 1,226 1,364 1,706 1,357 1,532 89.0 88.0 88.3 89.5 90.4 89.9 88.7 88.5 88.6 88.8 88.3 88.6 27.4 29.2 28.3 31.8 32.7 32.3 30.3 32.8 31.6 30.7 32.0 31.4 * These results are the average of 10 males, 10 females and the 20 of both sexes of these breeds. being used. The rest of the edible meat was then removed and added to the breast meat to obtain the total edible meat. This included the skin but not the giblets and neck meat. RESULTS Trial 1. In this trial, three production strains were compared to three broiler strains. A summary of the results of this trial appears in Table 1. An examination of the live s of the birds selected for this trial shows that, in every case, the males were appreciably heavier than the females at twelve weeks of age. These differences were found to be highly significant. It also may be noted that the live s of the production strain lots were significantly less than those of the broiler strain lots. The live of the Dark Cornish was significantly heavier than that of the White Plymouth Rocks. The two broiler strain s and the crossbred 10.6 11.4 11.0 13.1 12.6 11.3 12.8 11.4 12.8 A did not differ significantly at twelve weeks of age. The New York dressed s, expressed as a percent of live are given in Table 1. No great differences were apparent among the various breeds as to the percentage loss in the form of blood and feathers, although New Hampshire A females averaged 2.4 percent higher in New York dressed than did the B females (90.4 percent as compared to 88.0 percent). The edible meat is expressed as a percentage of the live. An examination of these percentages shows that the Dark Cornish yielded the highest percentage of edible meat of all the breeds studied. This difference was found to be highly significant upon analysis. In each case, except with the White Plymouth Rocks, the females tended to yield a greater percentage of edible meat than did the males. This difference was found to be highly significant also. In comparing the three strains

MEAT YIELD OE BROILERS 971 of s as to percentage of total edible meat, it was found that the production strain s and meat type A strain yielded a significantly higher percentage than did the meat-type B. The Crossbred A did not differ in percentage yield from that of the broiler New Hampshire A nor the production strain. It should be pointed out however, that even though the broiler strains yielded a smaller percentage of edible meat, the total of the edible meat yielded was greater than that of the egg strain lots because of the difference in live. The higher percentage yielded in the case of the Dark Cornish might be explained either by a smaller loss in viscera, a smaller skeletal structure, or a combination of both. Later unpublished data are available on this point. The White Plymouth Rocks ranked next to Breed Dark Cornish White Plymouth Rocks B A Crossbred B Crossbred A Sex* TABLE 2. A summary of the results of the statistical analysis of trial 1 Comparison Production vs Broiler strains Dark Cornish vs W. P. Rock Broiler N. Hamp vs Crossbreds Broiler N. Hamp A vs Broiler N. Hamp B Crossbred B vs Crossbred A TABLE 3. Summary of results of trial 2 (grams) 1,325 1,079 1,202 1,315 1,083 1,199 1,357 1,312 1,079 1,195 1,343 1,180 1,262 1,369 1,058 1,214 Total edible as % of live 51.1** 24.6** 4.2* 29.7** : F value beyond.05, significant. F value beyond.01, highly significant..9 Breast as % of live 57.9** j9 j**.5 15.1**.03 the Dark Cornish in percentage of edible meat yield, with the A, Crossbred A, and production strain New Hampshire yielding essentially the same percentages. The B yielded the lowest in this trial. These differences were statistically significant. As % of live wt. 90.7 90.2 90.5 90.1 88.1 89.2 89.2 88.6 92.5 90.5 90.1 92.5 91.2 89.4 87.8 88.6 72.8 73.7 73.2 71.2 68.1 69.8 69.5 68.4 69.2 68.8 70.2 71.9 71.0 71.6 70.0 70.9 Total edible as % of S ht 35.2 37.5 36.4 33.6 32.8 33.2 30.7 28.8 30.4 29.6 31.9 34.2 33.1 31.7 31.3 31.5 cfrlted 48.3 50.9 49.6 47.2 48.1 47.7 44.2 42.1 43.9 43.0 45.9 47.8 46.9 44.2 44.7 44.5 Breast yield as % of 13.2 14.6 13.9 13.0 12.5 12.8 10.7 10.3 11.4 10.9 11.0 12.8 11.9 11.1 12.0 11.6 Eviscer- ated New York dressed 18.2 19.8 19.0 16.9 18.3 17.6 15.4 15.0 16.5 15.8 15.9 17.9 16.9 15.5 17.1 16.3 * These results are the average of 10 males, 10 females, and 20 males and females of these breeds.

972 H. E. HATHAWAY, G. B. CHAMPAGNE, A. B. WATTS AND C. W. UPP The females yielded a higher percentage of breast meat in all cases than did the males. A summary of results of the statistical analyses for this trial is shown in Table 2. Trial 2. The Crossbred B strain was substituted for the production strain New Hampshires. No females of the New- Hampshire B breed were available for this study. A summary of the results of this trial appears in Table 3. It will be noted that in this trial the twelve week live of the males of all lots was considerably greater than that of the females. Statistical analysis showed this difference to be highly significant. There are no significant differences among the breeds as to live at twelve weeks probably due to the method of selecting the samples for slaughter in this trial. There were slight percentage differences among the lots in both New York dressed and in eviscerated. The highest New York dressed was approximately 91.2 percent (Crossbred B) of live. The highest eviscerated was 73.2 percent (Dark Cornish) of live, representing a 26.8 percent loss from dressing and evisceration. The differences among the lots with respect to eviscerated were not significant. However, the Dark Cornish tended to yield a higher percentage than did the others. Total edible was calculated as a percent of live (in Table 3) and also of eviscerated. It will be noted that the females yielded higher percentages of edible meat up to 2.3 percent more on the basis of live, except for the White Plymouth Rocks and the Crossbred A. The males and females of the Crossbreds A of this trial yielded practically the same percentage total edible. As observed in Trial 1, the White Plymouth Rock males yielded a higher percentage than did the females. When total edible is expressed as a percent of eviscerated, in every case, the females yielded higher percentages than did the males, ranging from 0.5 to 2.6 percent higher. Statistical analysis revealed that the differences between the sexes with respect to total edible based on live were not significant. However, analysis of the differences between the sexes with respect to total edible, expressed as a percent of eviscerated, showed that the females did yield significantly higher percentages of edible meat than did the males. The Dark Cornish again yielded the highest percentage of edible meat, both on the basis of live and of eviscerated. The Dark Cornish, both sexes, averaged 36.4 percent of live as compared to the lowest yield of 29.6 percent for A. The White Plymouth Rocks ranked next to the Dark Cornish in this respect. The females of the Crossbred B produced higher meat yields than did the females of the other lots except Dark Cornish, on the basis of live. However, they were slightly below the White Plymouth Rock females as regards percentage of eviscerated. In this trial, the B males yielded a slightly higher percentage total edible meat than did the A. It would appear that the high percentage yield of the Dark Cornish might be due to a smaller skeletal structure. In comparing the Dark Cornish and White Plymouth Rocks with the four broiler strains, statistical analysis showed that the Dark Cornish and White Plymouth Rocks, as a group, yielded a significantly higher percentage of total edible meat, both on the basis of live and of eviscerated. However, a comparison of the Dark Cornish and White Plymouth Rocks showed that the two breeds

MEAT YIELD OF BROILERS 973 TABLE 4. A summary of the results of the statistical analysis of trial 2 Comparison Production vs. Broiler Strains Dark Cornish vs. W. P. Rocks Broiler N. Hamp. vs. Crossbreds Broiler N. Hamp. A vs. Broiler N. Hamp. B Crossbreds B vs Crossbreds A Total edible as % of F value 24.8** 8.6** 8.1** 2.2 3.8 * F value beyond.05, significant. ** F value beyond.01. highly significant. differed significantly when total edible was expressed as a percent of eviscerated. A comparison of the percentage value of the four broiler strains showed that the Crossbred B yielded the highest percentage of edible and that the B, A and Crossbred A did not differ significantly in these respects. The lots ranked the same in regard to percentage breast yield as they did with percentage total edible on the basis of both live and eviscerated s. Table 4 gives a summary of the results of the statistical analysis of this trial. Trial 3. It can be observed in Table 5 that the twelve week old s of the males in all lots are again significantly greater than those of the females. It can be noted that the live s of the two non-broiler strain lots were significantly less than those of the four broiler lots. The difference in the live s of the Dark Cornish and the White Plymouth Rocks was not significant, nor did the four lots of broiler stocks differ significantly one from the other (see Table 6). There were no great differences among the lots in New York dressed s, although a range of 3.4 percent may be F value 43.6** 2.2 *7.3** 3.8 j 7** Breast as % of F value 103.1** 39.9** 17.9** 2.1 5.4* F value 63.7** 14.0** 1.3 11.2** 5.3* noted between the highest group, Dark Cornish males, and the lowest group, White Plymouth Rock females. Statistical analysis of the eviscerated s showed that the Dark Cornish yielded a significantly higher percentage eviscerated on the basis of live (72.7 percent) than did the White Plymouth Rocks (68.7 percent). The Dark Cornish averaged significantly higher in eviscerated s than any of the other lots. The percentage eviscerated of live for the A, (70.9) and Crossbred B, (71.3) was significantly greater than was that of the B, (69.7). Percentages of total edible meat yield of live and eviscerated s are also found in Table 5. In this trial, all females yielded a higher percentage of total edible meat on the basis of both live and of eviscerated s. The same is true for the percentage of breast on the basis of live and eviscerated. Statistical analysis shows the difference between the sexes was highly significant. The Dark Cornish again ranked highest in percentage total edible meat yield on the basis of both live (3S.2 percent) and of eviscerated (48.5 percent) s. The New

974 H. E. HATHAWAY, G. B. CHAMPAGNE, A. B. WATTS AND C. W. UPP TABLE 5. Summary of results of trial 3 Breed Sex* (grams) Total edible as % of New York Eviscerdressed ated as % of live Breast yield as % of Evis- ' cerated Dark Cornish 1,311 976 1,144 90.7 90.1 90. 73.4 71.8 72.7 35.1 35.3 35.2 47.8 49.1 48.5 13.5 14.6 14.1 18.4 20.3 19.4 White Plymouth Rocks B A Crossbred B Crossbred A 1,228 1,066 1,147 1,534 1,152 1,343 1,591 1,286 1,439 1,713 1,337 1,525 1,642 1,208 1,425 88.9 87.3 88.2 89.4 87.9 88.8 90.3 88.5 89.5 88.7 89.9 89.3 87.8 88.2 88.0 69.1 68.3 68.7 69.8 69.6 69.7 71.3 70.9 71.1 70.9 71.8 71.3 68.3 69.9 69.0 30.6 30.9 30.8 30.0 31.0 30.5 31.0 32.6 31.8 33.7 35.3 34.5 30.3 31.2 30.8 44.3 45.2 44.8 43.0 44.6 43.8 43.5 46.2 44.9 47.5 49.1 48.3 44.4 44.6 44.5 11.3 11.7 11.2 12.4 11.8 11.6 12.7 12.2 14.6 13.4 11.0 11.6 16.3 17.7 17.0 16.1 17.7 16.9 16.3 18.0 17.2 17.1 20.3 18.7 16.1 17.3 16.7 * These results are the average of 10 males, and 10 females, and 20 males and females of these breeds. Hampshire B were the lowest of the lots in these respects (30.5 percent on live basis and 43.8 percent on eviscerated basis). Statistical analysis reveals that these differences among lots were significant. Comparison Production vs. Broiler Strains Dark Cornish vs. W. P. Rocks Broiler N. Hamps. vs. Crossbreds Broiler N. Hamps. A vs. Broiler N. Hamps. B Crossbreds B vs. Crossbreds A The Dark Cornish again ranked highest in percentage breast yield expressed as a percent of live and of eviscerated s, followed by the Crossbred B strain. Crossbred A yielded the lowest of the lots in percentage breast. The differences TABLE 6. A summary of the results of the statistical analysis of trial 3 Total edible as % of 14.5** 13.3** 87.4** 36.5** 18.1** 24.7** 7.5** 4.2* 61.9** 38.3** Breast as % of 9.2** 48.0** 4.1* 1.1 28.9** 8.0** 25.3** 4.2*.2 18.5** * beyond.05, significant. ** beyond.01, highly significant.

MEAT YIELD OF BROILERS 975 in percentage breast yield for the different lots were found to be significant upon analysis, except for the difference between the two broiler strains of s Table 6 shows a summary of the results of the statistical analysis of trial 3. DISCUSSION It was found that the males were heavier than the females in live at twelve weeks of age as expected. The nonbroiler strains were in general always lighter than the broiler strains at that age. No significant differences were noted among the lots as to percentage loss from Breed Dark Cornish White Plymouth Rocks B A Egg Strain Crossbred B Crossbred A highest percentage of total edible meat and of breast meat on the basis of live and of eviscerated. This agrees with the results of Henderson (1950) in which he reported the Dark Cornish ranking highest in meat type score. However, Maw (1939) was unable to find significant advantages of Dark Cornish hens over Rhode Island Red hens. The White Plymouth Rocks were second to the Dark Cornish in all trials, except in trial 3, in which Crossbred B ranked second in that respect. The lots were consistently low in meat yields, both total edible and breast meat. TABLE 7. Average dressed measurements* of male and female 12 week old broilers Keel length 9.4 10.0 10.4 11.0 9.4 9.5 Trial 1 Body depth 9.6 10.0 10.7 11,0 10.2 9.7 * Centimeters. ** No female are included in this group. Breast width 3.6 3.2 3.4 3.5 3.1 3.4 live to New York dressed. yields of the pullets were less than those of the males, due to their smaller size. Jaap et al. (1950) reported the same results in that respect. s obtained in trial 2 and trial 3 indicated significant differences among the strains with the Dark Cornish yielding the highest percentages, both on the basis of live and of eviscerated s. The females, in general, yielded higher percentages of edible meat yields than did the males. Frischknecht and Jull (1946) reported the same results in their studies with 12 week old chickens. The Dark Cornish, in all trials, yielded the Keel length 9.4 9.6 10.5** 9.7 9.8 9.6 Trial 2 Body depth 9.6 10.0 10.4** 10.0 10.1 9.8 Breast width 3.4 2.9 2.8** 2.8 3.0 2.9 Keel length 9.3 10.0 10.2 10.4 10.6 10.3 Trial 3 Body depth 10.2 11.0 10.7 11.5 11.6 10.8 Breast width 3.0 2.5 2.7 2.9 3.2 2.9 The Crossbreds appeared to be intermediate in most trials, except in trial 3, where the Crossbred B ranked second to the Dark Cornish. Although the Dark Cornish were the lightest in live at 12 weeks, they had wider breasts than did the other lots. Table 7 shows the average measurements for each lot for the three trials of this experiment. It will be noted however, that the keel length and body depth of the Dark Cornish were.less than those of the other lots. The.broiler type s, although heaviest in live, had a narrower breast but a longer keel and a deeper body. Frischknecht and Jull (1946) reported the mean

976 H. E. HATHAWAY, G. B. CHAMPAGNE, A. B. WATTS AND C. W. UPP TABLE 8. Correlation of breast with heel length, body depth and breast width Breast lenj th d & Breastwidth v X, X, * Correlation Breast Weight X Standard Regressions.4673.1091.4355.4021.6442.6505 R =.8032 Correlation Breast Weight X Standard Regressions.2992.4569.2544 -.1138.4634.5448 R =.6002 breast widths greater in the progeny of Dark Cornish males. Bird (1948) demonstrated that roundness of breast was inherited chiefly from the male. Simple and multiple correlations of breast with keel length, body depth, and breast width are shown in tabular form in Table 8. From this table it can be noted that breast is more highly correlated with breast width than is breast with either keel length or body depth. Asmundson (1944) also found that breast width was the only measure needed to differentiate the yields expected from turkeys. The correlation of the three measurements, keel length, body depth, and breast, is somewhat but not a great deal higher than the simple association of breast width and breast. This indicates definitely that breast width is the best single measure for predicting breast, and that using the other measurements in addition is not worthwhile. SUMMARY AND CONCLUSIONS One thousand eight hundred chickens were grown to twelve weeks of age in three trials. Samples of ten males and ten females per lot were dressed and meat yield studies made on a total of 350 carcasses. Production or non-broiler strain stocks were compared with several broiler stocks. Certain body measurements, namely keel length, body depth, and breast width were obtained and selected samples were weighed, processed, and deboned for observation. The following results were obtained: 1. in each lot weighed approximately 20 percent heavier than the females at twelve weeks of age. The broiler strains averaged heavier than the nonbroiler strains at that age, as might be expected. Differences in live among lots were significant, except in trial 2. In this trial the samples were selected on an over-all uniform basis. 2. The Dark Cornish yielded the highest percentage of total edible meat and breast meat based on live and on eviscerated s. The White Plymouth Rocks ranked second to the Dark Cornish, except in trial 3. The Crossbreds in general were intermediate in meat yields in all trials, except in trial 3, in which B strain Crossbred ranked second to the Dark Cornish. The broiler stocks were consistently low in meat yields, with the two strains varying from trial to trial. 3. Body measurements on these birds indicated that the Dark Cornish, although smaller in live at twelve weeks, had the greatest breast width. The keel length and body of the the Dark Cornish, however, were the smallest of the lots. The lots, which were heavier in live, had consistently narrower breasts. On the other hand, they had longer keels and greater depth of body, yet yielded a lower percentage of meat than did the Dark Cornish. 4. Statistical analyses indicate that breast width is the best single measure for predicting percentage breast meat and total edible meat yields in twelve week old chickens. REFERENCES Asmundson, V. S., 1944. Measuring strain differences in the conformation of turkeys. Poultry Sci. 23: 21-29.

PHOSPHORUS REQUIREMENTS or HENS 977 Bird, S., 1948. Quantitative determination and segregation of breast conformation in poultry. Poultry Sci. 27:506-508. Broadbent, M., and H. W. Bean, 1952. The yield of edible meat from turkeys, ducklings and differend market classes of chickens. Poultry Sci. 31: 447-450. Brown, P. B., and H. W. Bean, 1952. The yield of edible meat from different market classes of chickens. Poultry Sci. 31: 232-234. Essary, E. O., S. J. Mountney and O. E. Goff, 1951. Conformation and performance in standardbred and crossbred broilers. Poultry Sci. 30: 552-557. Frischknecht, C. D., and M. A. Jull, 1946. Amount of breast meat and live and dressed grades in relation to body measurements in twelve week old purebred and crossbred chickens. Poultry Sci. 25: 330-344. Gilbreath, J. C, and C. W. Upp, 1952. The growth pattern of the Cornish fowl. Louisiana Agr. Exp. Sta. Bui. 464. Hathaway, H. E., 1953. Comparing processing yields of various broiler strains (Preliminary report). The Southeastern Poultryman 6: (1) 39, 113-115. Hathaway, H. E., 1952. Test shows possibilities of improving meat yields. Birds from 1951 National C.O.T. used in Louisiana experiment. Broiler Growing, 3(10): 46-48. Henderson, E. W., 1950. Breed differences in meat type score and of twelve week old THE phosphorus requirement of laying hens has not been adequately defined. Earlier work at this Station indicated that 0.5 percent of phosphorus in the ration was insufficient to maintain egg production and egg shell strength but 1 Supported in part by a grant-in-aid from the International Minerals and Chemical Corporation, Chicago, Illinois. A preliminary report of this work was made at the Ninth World's Poultry Congress, Paris, 1951. 2 Present address: Central Research Laboratory, International Minerals and Chemical Corporation, Skokie, Illinois. cockerels. Michigan Agr. Exp. Sta. Quart. Bui. 32: 507-512. Jaap, R. G., M. M. Renard and R. D. Buckingham, 1950. Dressed and eviscerated meat yields from chickens at twelve weeks of age. Poultry Sci. 29: 874-880. Jull, M. A., and W. A. Maw, 1923. Determination of the dressed, drawn and edible percentages of various kinds of domestic birds. Sci. Agr. 3: 329-338. Jull, M. A., R. E. Phillips and C. S. Williams, 1943. Relation between cut-up chicken proportions and prices. U. S. Egg Poultry Mag. 49: 122-124. Lowe, B., 1941. Edible meat from two s of roasters comparing yields from forty-three to forty-seven pound and forty-eight to fifty-four pound classes of roasters. U. S. Egg Poultry Mag. 47: 95-102. Maw, W. A., 1939. Poultry meat studies at Mac- Donald College. Canadian Soc. Tech. Agr. Review (June): 60-64. McNally, E. H., and N. H. Spicknall, 1949. Meat yield from live, dressed and eviscerated Rhode Island Red males of broiler, fryer and light roaster s. Poultry Sci. 28: 562-567. Stotts, C. E., and M. I. Darrow, 1953. Yields of edible meat from Cornish crossbreds, non-cornish crossbreds and purebred broilers. Poultry Sci. 32: 145-150. Phosphorus Metabolism and Requirements of Hens 1 M. B. GILLIS, 2 L. C. NORRIS AND G. F. HEUSER Agricultural Experiment Station and School of Nutrition, Cornell University, Ithaca, New York (Received for publication March 5, 1953) that 0.75 percent was adequate for these purposes (Norris, Heuser, Wilgus and Ringrose, 1933). Miller and Bearse (1934) obtained greater egg production with a ration containing approximately 0.8 percent phosphorus than with one containing 0.6 percent of this element. Evans and Carver (1942) reported that 0.8 percent of phosphorus gave better results than 0.6 or 1.2 percent when the ration contained 2.5 percent calcium. However, they found little difference between 0.6 and 0.8 percent phosphorus in a ration containing only 1.5 percent cal-