Estimating Age at Sexual Maturity from Flock Records

AGE at sexual maturity has long been recognized as an important component of egg laying performance. However, in most random sample egg laying tests and other types of performance tests maturity cannot be measured directly on individual birds because only pen records are kept. In this case age at 50 percent egg production is usually taken as the criterion of maturity. We may argue that the 50 percent production level is a good choice because, for any level less than 50 percent, not as many birds will enter the estimate. Then it follows that 60 percent production should be better still because it would include more birds than the 50 percent production level. On the other hand, if the pen cannot reach 60 percent production because of disease or other causes, then the age at which the pen reaches some lower level would need to be used. Several different measures …