The pattern of growth from hatch to sexual maturity was measured in quail, chicken, and turkey females using the Gompertz equation. Quails and chickens were selected for high or low immature BW and turkeys were selected for high BW. Quail and turkey species also included their respective randombred control populations. The chicken species included an F2 of the selected lines. Thus, there were considerable differences in BW not only among species but between lines within species. Differences were evident at hatch as hatch weights relative to asymptotic BW were greater for quail than chickens and turkeys. Age and BW traits associated with point of inflection (POI) were variable. Species differences appeared to be influenced by the selection scheme applied to the populations. Slope at POI was greatest in quail and the same for turkeys and chickens. Age at 90% of the asymptotic BW was generally greatest for chickens, intermediate for turkeys and lowest for quails. Selection age in relation to age at POI may contribute to the timing and magnitude of growth response observed.

From a randombred control population of Coturnix coturnix japonica, four strains were selected respectively for high and low 4-week body weight and high and low total plasma phosphorus (plasma yolk precursor). Based on seven generations of selection, die realized heritabilities plus or minus their standard errors for high and low body weight strains were .37 ± .05 and .44 ± .28, respectively. The total gain and gain per generation were greatest in the low weight strain, primarily due to greater selection differentials.Selection for plasma yolk precursor was more effective in the high than low strain. The respective realized heritabilities plus or minus standard errors were .32 ± .02 and .34 ± .03. The selection differentials were larger in the high strain than in die low strain. There was no significant change in plasma yolk precursor in the weight strains nor in 4-week body weight in die plasma yolk precursor strains, which indicated that the genetic correlation between body weight during the growing period and plasma yolk precursor during the laying period was close to zero. (

Body weight and breast width have been greatly increased in the modern turkey. However, the relative amounts of leg muscles and leg bones have declined. A similar decline also occurs with age. It was theorized that this is an inherent weakness that magnifies other causes of leg problems. In an attempt to increase the relative amount of leg bone, a subline (FL) was developed by mass selection for increased shank width at 16 weeks of age from a long-term growth-selected line of turkeys (F). Shank width of FL was increased greatly by selection. The realized heritability of shank width, based on the regression of accumulated selection response on accumulated selection differential, was .33 +/- .05 over five generations of selection. Body weight of males from FL increased at a rate comparable to that of F at 16 weeks of age. However, there was no comparable improvement in body weight of FL females, resulting in a significant line X sex interaction. A similar interaction was observed for body weight at 8 and 20 weeks of age in these lines. The genetic increases in shank width in FL resulted in significantly improved walking ability of males at 16 weeks of age in comparison to F, even though body weight of males from the two lines was similar. The walking ability of FL did not change relative to the control line from which F originated. Thus, large genetic increases in body weight of males can be achieved without loss in walking ability by genetic increases in shank width.(ABSTRACT TRUNCATED AT 250 WORDS)

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