LIMITED TRAPNESTING 3 



Dudley found the correlation between annual production and the production 

 on four consecutive days to be about .93 in Leghorns and .85 in Wyandottes; 

 between annual production and production for one day weekly, .91 for Leghorns 

 and .92 for Wyandottes. The regression of annual production on the production, 

 observed by either short-time measure was not exactly linear. The number of 

 eggs laid in either short period did not give an accurate estimate for the low 

 producers or for the higher producers, but was satisfactory for the medium pro- 

 ducers. 



By applying regression lines, Dudley secured the following results: 



Percentage of Birds 

 Difference Between by the Two Measures 



Estimated and Actual 

 Annual Production 



0-12 eggs 



13 — 24 eggs 



25 - 36 eggs 



37 eggs or more.. 



In his study the correlation between annual egg weight and egg weight records 

 obtained by either short measure was .95, and they were equally good for cal- 

 culated annual egg weight. Regression was linear for both. 



Thompson (1933) u ed the records of 3937 White Leghorn pullets, hatched in 

 1929 and 1930 and entered in New Jersey egg-laying contests, to study the relative 

 efficiency of three short-time trapnest records: the first 120-day record; the last 

 30-day record from August 25 to September 23 at the close of the year; and a 

 combination of the two. He stressed that regression of annual production on the 

 production of all these short periods was non-linear and developed a curved re- 

 gression line which seemed (o be satisfactory for estimating the probable annual 

 record from a known short-time record. 



Thompson and Jeffrey (1936) applied three partial trapnest measures to the 

 annual contest records of 2028 White Leghorns: (a) winter production (Oct. to 

 Feb. 1); (b) summer-fall production (June to Oct. 1); and (c) a and b combined 

 as one measure. The correlation between winter and annual production was 

 +.7075 c ratio; between summer-fall and annual production +.8017 c ratio; 

 and between winter plus summer-fall and annual production .9368 c ratio. A 

 curved regression line was calculated for the three measures and the third was 

 found to be the most accurate for predicting annual production. When the 

 winter and summer-fall records were applied to 100 hens, 46 percent of the birds 

 showed a difference between predicted and actual annual records of from to 9 

 eggs; 25 percent, from 10 to 19 eggs; 12 percent, from 20 to 29 eggs; and 17 per- 

 cent, 30 eggs or more. A comparison of these results with those of Dudley seems 

 to indicate that Dudley's measures of one day weekly and four consecutive 

 days each month are a slightly better criterion of annual production than the 

 winter and summer-fall record used by Thompson and Jeffrey. 



Olsen (1939) reported on the record of 500 White Leghorns and 390 Rhode 

 Island Reds at the Beltsville Research Center, using two short-time measures: 

 trapnesting one day a week throughout the year; and trapnesting one day a week 

 through August and daily in September to the end of a 52-week laying year. He 

 obtained a correlation of .91 in Leghorns and .89 in Rhode Island Reds between 

 the number of eggs laid in one-day-a-week trapnesting and the annual record. 



