In vivo nuclear magnetic resonance (NMR) imaging and spectroscopy techniques were used to monitor changes in P- and H-containing molecules in embryos of two broiler strains (30 and 31) differing genetically in fat content and ranging in age from 0 to 20 days of incubation. Chemical analysis showed that Strain 30 has more carcass fat than Strain 31 at market age (7 wk). Proton (1H) and 31P spectra were obtained on four eggs per strain at Days 0, 2, 4, 6, 8, 11, 12, 14, 16, 17, 19, and 20 of incubation. Fat:water, phosphomonoester (PME):phosphodiester (PDE), and adenosine triphosphate (ATP):PDE ratios were calculated. Chicks were hatched, grown to market weight (2,000 g for females and 2,300 g for males at 7 wk), and the whole intact carcasses were analyzed for crude fat. Hydrogen-1 NMR spectroscopy studies of incubated eggs indicated no significant difference (P > .05) in the fat:water ratio between the two strains. The difference in the PME:PDE ratios between the two strains as obtained by 31P-NMR spectroscopy over all days of incubation analyzed was not significant (P > .05); however, there was a significant difference in this ratio between the two strains at Days 4, 6, and 11. Up to Day 16, Strain 30 had a slightly, but not significantly (P > .05), higher ATP:PDE ratio as shown on 31P-NMR spectra, whereas after Day 17 the ATP:PDE ratio was significantly higher (P < .01) for Strain 31. Strain 31 birds had a significantly lower (P < .05) crude fat content. There was a significant difference (P < .05) in 7-wk carcass fat content between sexes, males having significantly (P < .01) less fat than females, which was correlated with a significantly higher (P < .01) ATP:PDE ratio in male embryos. It might be possible to use ATP:PDE ratios obtained during embryonic development by 31P-NMR to select strains of birds for low fat content at market weight and to distinguish between sexes during late embryonic development.

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Three studies were conducted with birds dubbed at hatch vs. dubbed and dewattled at 118 days or 255 to 260 days of age or with normal hens. In the first, involving 5928 pullets of four strains housed 1 per cage, dubbing and dewattling at 255 to 260 days caused small adverse effects on egg numbers as compared with nondubbed controls. Body size was reduced, and both egg weight (EW) and shell strength were increased slightly. In the second study, involving 8180 pullets of nine strains housed 1 per cage, dubbing and dewattling at 118 days slightly increased survivor egg production (SEP) and laying house mortality, and reduced age at first egg, 240-day EW, and 450-day Haugh units (HU), as compared with dubbing only at hatch. There were significant strain by dubbing treatment interactions for hen-day rate of lay (HDR) and SEP. In the third study, involving 1824 pullets of three strain crosses housed 2 and 3 birds per cage (three different cage sizes), there were no significant differences between birds dubbed at hatch and those not dubbed. Variation in age at 50% production, SEP, and HDR was reduced for the dubbed groups. These studies show that the older the birds are when dubbed, the greater the negative effects of dubbing. Hens dubbed at hatch exhibit no effects with the early dubbing or adverse effects in the laying house.

The relationship of the reproductive performance and semen characteristics of commerical broiler parent males with their body weight at 6, 8, 10, and 12 weeks of age, keel length, shank length, breast angle at 8 weeks of age, and packed erythrocyte volume at 6 and 8 weeks of age were examined. Phenotype correlations of juvenile traits with subsequent reproductive traits were generally of low magnitude, except for the significant positive correlations of 6- and 8-week body weight with fertility. Positive correlations existed between fertility and semen quality traits which were significant in some cases. Six-week body weight and spermatozoal motility appeared to be the most useful traits in predicting a male's fertility.