66 



SCIENTIFIC AGRICULTURE. 



February, 1921. 



edly to be found in tlie fact tbat one of the factors 

 used (thickness of pelvis) is not related to total past 

 production in the manner assumed in this "system", 

 while the correlation of the other two is so small that 

 they are of greatest value onl_y when considered with 

 other characters. 



WEIGHT OF BIRDS. — That hens of the same 

 breed but varying iu weig^it are good layers without 

 apparent relation to weight ha.s been shown by trap- 

 iie.st records. Some work ha.s, however, been done 

 recently by Lewis (6) and his a-ssociates at Ibe New 

 Jei-sey Experiment Station indicating that birds with- 

 in certain weight limits give a higher average produc- 

 tion than those weighing more or less. This weight is 

 found to be apprcximately 3.25 to 4.75 pounds for 

 Leghorns. 



In order to get data on this point, the first three 

 coefficients of correlation in table 7 were worked out. 

 It will be seen from these that there is undoubtedly 

 a significantly positive correlation between weight of 

 birds and their production. The rea.son that the first 

 coefficient of correlation is not greater is that the 

 heaviest birds are comparatively poor producers. 



In graph 2 the birds are divided into one-third 

 pound cla.sses. This graph s;iows that birds weighing 

 from 3 1-3 to 4 1-3 pounds had a significantly higher 

 mean production than those weighing moi'c or less. 

 The birds weighing from 3 to 3 1-3 pounds also show 

 a mean production above that for the whole flock, 

 w/iich would seem to indicate that the best producers 

 averaged somewhat less in this flock than birds of 

 the same breed at the Viuelaud Contest. Obviously 

 birds weighing less than 2 1-3 pounds are of little 

 value a« layers. 



BROODINESS. — Broodiness is a charcteristic of 

 fowls that varies a great deal in different varieties 

 and in different strain-s. The riiother instinct is more 

 hig'hly developed in the Asiatic cla-ss liiiau the Amer- 

 ican, while the White Leghorn and most of the Med- 

 iterranean class are considered as practically nonsit- 

 ters. That this is not always tjie ease is .shown by 

 the fact that of the 280 birds involved in this ex- 

 periment, 107 were broody from one to seven times. 



In order to get an idea of what effect this had on 

 production, the birds were divided in two cla.sses, 

 those that had not been broody and those t.hat had 

 been broody one or more times. The mean production 

 for the broody hens was 120.7760±2.6290 eggs and 

 146. 5720±2. 1958 eggs for non-broody hens, a differ- 

 ence of over twenty eggs in favor of the latter. This 

 result is contradictory to that of Patterson and Quis- 

 enberry (7), their figures showing a somewhat ^iiigher 

 production for broody hens. Broodiness apparently 

 varies with age as well as varying for different breeds 

 and strains, so that considerable variation is to be ex- 

 pected with different flocks. 



It would .seem, from the results of this experiment, 

 that it is decidedly worth while to find some way 

 of distinguishing the broody from \}\c nonbroody hens. 



The mean thickness of pelvis for the broody and non- 

 broody hen.s wa.s 



8.4661 ±.0078" 6.5011 ±.0038" 



and 



32 32 



, respectively. 



The pelvis or body wall of the broody hens is there- 

 fore decidedly thicker than that of the nonbroody 

 .hens as shown by the mean. This result is explained 

 largely by tlie mean eg-g production from Julv 1 to 

 October 31. This was 28.8600± 1.2459 and 37."9880± 

 1.1384 eggs for the broody and nonbroody hens res- 

 pectively, a difference of about niMe eggs in favor 

 of the latter. 



In order to find whether any of the other charac- 

 teristics studied varied with respect to previous brood- 

 iness. averages of the other measurements were made. 

 Thase are tabulated in t|ie following table and indicate 

 that there is practically no significant difference in 

 any of these. 



Table 8. 



Broody Non-broody 

 Average. Average. 



1. Length of Keel 9.69 cm 9.71 cm 



2. Length of Keel -^ Weight .00689 .00677 



3. Weight 1443.8 grants 1462.3 grams 



4. Width at Hips 6.60 cm 6.65 cm 



5. Back — Posterior 



end of Keel 11.09 cm 11.25 cm 



Size of Egg. 



Benjamin (3) found that there was a strong cor- 

 relation between size of c^ick and size of egg and that 

 this relation persisted for over two years of the bird's 

 life thougb gradually decreasing with age. Atwood 

 (2) also rei)orts similar i-e.sults. Kent (5) found that 

 there is a decided relation between weig-ht of egg and 

 weight of bii'd, thu.s completing the cycle. This latter 

 result is confirmed in table 9. It will be noted that 

 length of keel is significantly correlated with size of 

 egg. The next coefficient of correlation in table 9 

 shows that tjiiere is no relation to total production. 

 Egg weight also .shows a decided correlation to the 

 depth of the body, abdomen and other measurements 

 that showed a relation to egg jiroduction, although 

 there is no direct relation between the two. Tyiis 

 .same result was obtained by Kent (5) in a study of 

 comb characters. 



F'rom these results it will be seen that where birds 

 are selected for greater production based on anato- 

 mical characters correlated with production, they * 

 are also selected for size of egg. It should be noted 

 that length of keel is correlated to size of egg but 

 not to number of eggs laid, .so that it would no doubt 

 be worth wjiile to .select birds with long keels because 

 of the relation to size of egg. It would seem that a 

 large roomy body is indicative of a tendency to lay a 

 large egg as well as to lay a large number. Except 

 for weight of bird, the relation of the different char- 



Table 7. 



Subject. 

 Weigbt- of 



Relative 



Coefficient of 

 Correlation. 



: 2278±.0382 



2550±.0377 



2027±.0386 



3146±.0363 



6851±.0214 



Lenoth of Keel Size of Abdomen — .2345±.0381 



Bird Total Egg Production 



" Highest Monthly Egg Production 



No. of Months Laid 



" Length of Keel 



Width at Hips 



