Estimation of performance efficiency in the laying hen

Relationships between body composition and reproductive performance in the laying hen

“…(1947), El-Ibiary and Shaffner (1951), Abplanalp £t al. (1960), Merritt andGowe (1962), Merritt (1966), Casey (1970) and Silva (1974) were in the same range as those cited by Kinney (1969) for body weight. The genetic correlations between shank length and body weight were generally found to be of an intermediate to high order.…”

Weighted least squares estimates of genetic parameters in chickens

“…The heritability estimates of shank length are in the same range as those estimated for body weight (Lerner et ^., 1947, El-Ibiary and Shaffner, 1951, Abplanalp et ^., 1960. Casey (1970) found an average heritability of 0.44, 0.39 and 0.49 for shank length, condition index (BW/SL) and housing body weight, respectively. Because of the high correlation between condition index and body weight he concluded that the condition index is influenced by the same effects as body weight itself.…”

“…Snyder (1945) and Olsen and Knox (1940) reported that egg weight responds well to (Waters and Weldin, 1929, Festing, 1964, Casey, 1970. After the third generation of selection Shultz (1953) found that the response to selection was still strong.…”

“…Because a full descrip tion of line A has been given by both Testing (1964) andCasey (1970), only a short review will be given here.…”

Relationships between body composition and reproductive performance in the laying hen

“…Cock (1969) derived an index of relative shank length, i.e., (shank length) -0.4 (log body weight), where 0.4 is the approximate average value of the coefficient of ontogenetic allometry during postnatal growth. Casey (1970) proposed a condition index which was essentially the inverse of Jaap's (1938) index. The estimated heritability of his index was 0.08.…”