Cobb 500 broiler breeder females (n = 832), which had been raised to achieve a typical 20-week body weight of 2.1 kg, were subjected to an abrupt or gradual increase in photoperiod to determine the effects on reproductive performance. One group (n = 416) was reared on 8-h photoperiods till 19 weeks and abruptly transferred to 16-h photoperiods. Another group (n = 416) was reared on 8-h photoper...

The main goals of layer breeding are a result of eeonomie eonditions. GOWE et al. (1993) reported that in egg stock seleetion programs the key traits are egg produetion rate, age at sexual maturity, viability at all ages, egg size, egg shell strength, feed effieieney as weil as fertility and hatehability. However, in praetiee, laying intensity is usually the main seleetion eriterion (WJ,;:ZYK, ...

OBJECTIVE To provide clinically meaningful, normative reference data that describe the timing of sexual maturity indicators among a national sample of US children and to determine the degree of racial/ethnic differences in these estimates for each maturity indicator. METHODS Tanner staging assessment of sexual maturity indicators was recorded from 4263 non-Hispanic white, black, and Mexican A...

Dr. RAYMOND PEARL (1912) was the first worker to suggest that sexlinked factors were involved in the inheritance of fecundity. PEARL used as a measure of fecundity the eggs produced during the winter period. He proposed that two major dominant factors were responsible for high egg production, one of which resided in the sex chromosome. GOODALE (1919) and HURST (1921) each failed to confirm the ...

Traditional poultry production has changed to a considerable industry after few decades. Now, poultry industry is one of the main sectors to obtain the required protein for human consumption. Prediction of the weight and number of eggs according to economic traits can improve the efficiency of production and the profit of producers. In present study, the weight and number of eggs in Mazandaran ...

Traditional poultry production has changed to a considerable industry after few decades. Now, poultry industry is one of the main sectors to obtain the required protein for human consumption. Prediction of the weight and number of eggs according to economic traits can improve the efficiency of production and the profit of producers. In present study, the weight and number of eggs in Mazandaran ...

Traditional poultry production has changed to a considerable industry after few decades. Now, poultry industry is one of the main sectors to obtain the required protein for human consumption. Prediction of the weight and number of eggs according to economic traits can improve the efficiency of production and the profit of producers. In present study, the weight and number of eggs in Mazandaran ...