Selection for Body Weight at Eight Weeks of Age

Siegel, P. B.

doi:10.3382/ps.0420896

Cited by 51 publications

(13 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A major one is the difficulty in increasing hatching egg production in meat-type populations (McClung, 1958;Jaap era/., 1962;Shoffner, 1965, 1967;Siegel, 1963). This may be due to not distinguishing between normal and certain abnormal eggs.…”

Section: Introductionmentioning

confidence: 95%

Selection for Body Weight at Eight Weeks of Age

Siegel

1976

Poultry Science

Self Cite

View full text Add to dashboard Cite

Two experiments were conducted to study oviposition patterns and ovarian activity at various physiological ages in S15 and S16 generation pullets from lines selected bidirectionally for high (HWS) and low (LWS) juvenile body weight. The fixed periods of lay for random samples of pullets from the date of first egg were 20, 40, 60, and 80 days in the first experiment and 40, 80, 120, and 160 days in the second experiment. HWS pullets matured significantly earlier than LWS pullets in both generations. The frequency and the percentage hen-day production (%HDP) of defective eggs were significantly greater in the HWS than LWS line in both generations. Delayed sexual maturity did not significantly change the pattern of defective egg production for a fixed period of lay. In the HWS line the %HDP of defective eggs progressively increased until about 40 days of lay and tended to decline thereafter, while in the LWS line the percentage decreased from 20 to 40 days and then stabilized. The frequency of normal unbroken eggs to 80 days of production did not differ among lines either in the S15 or S16 generation. When measurements were extended to 160 days of lay in the S16 generation HWS pullets produced significantly more normal eggs than LWS pullets. Possible effects of ovarian activity on the egg production pattern during the laying cycle are discussed. There was a significantly higher incidence of internal laying and atrecia of the growing follicles in the HWS than in the LWS pullets. Ovarian activity, evidenced by the number of developing and ruptured follicles, was significantly greater in the HWS than the LWS line, as was the incidence of ova developing in pairs. Product moment correlations and multiple regressions among the measurements of ovarian activity were calculated within lines. In the HWS line, 62.5% of the variation in %HDP of defective eggs could be accounted for by the %HDP of normal eggs and the number of developing follicles while in the LWS line these variables accounted for only 7.29% of the variation in %HDP of defective eggs.

show abstract

Section: Introductionmentioning

confidence: 95%

Selection for Body Weight at Eight Weeks of Age

Siegel

1976

Poultry Science

Self Cite

View full text Add to dashboard Cite

show abstract

“…Since selection intensity applied to males is usually very much higher than that applied to females, testing only the males would utilise limiting resources more efficiently. Furthermore, since there is a moderately large positive correlation between 4-to 6-and 8-to 10-week body weight (Siegel, 1963;Merritt, 1966;Wilson, 1969;Pym and Nicholls, 1979), preliminary selection of males on the basis of 4-or 5-week weight could be exercised, and only the best males tested in single cages for individual food consumption. Obviously a reduction in the number of chickens tested decreases the selection intensity, but provided the proportion of males tested is not too small, the loss should not be very significant since those selected for testing probably have the higher indices.…”

Section: Predicted Responses To Selectionmentioning

confidence: 99%

Selection for food conversion in broilers: Predicted responses to selection for economic efficiency

Pym

James

1979

British Poultry Science

View full text Add to dashboard Cite

“…Influ-S EVERAL studies have shown that body weight in chickens can be readily increased or decreased by selection (Siegel, 1962;Maloney et al, 1963;Festing and Nordskog, 1967). Also, concurrent with changes in body weight are correlated changes in other traits (Siegel, 1963;Maloney et al, 1963;Ideta and Siegel, 1966;Festing and Nordskog, 1967).…”

mentioning

confidence: 89%