Four experiments were conducted to determine the effect of light during incubation on embryonic and post-embryonic development of broiler chickens. The eggs were randomly assigned to one of three lighting regimes during the incubation period: (a) a diurnal light cycle consisting of a 12-hour light period followed by a 12-hour dark period (12L-12D), (b) 24 hours of light (24L-OD), and (c) 24 hours of darkness (0L-24D) per day.The development of the embryos was accelerated by increasing the length of exposure to light during incubation. There were no significant differences between treatments in initial body weights of those chicks that hatched early and those which required 21 days to hatch. Body weights of the chickens at four and eight weeks post-hatch showed no significant differences between treatment groups. Embryo weights at 12 and 18 days of incubation were heavier when increased amounts of light were provided during incubation. The incidence of healed navels was increased with greater length of exposure to light during incubation.From these data it was hypothesized that the rate of embryonic development, as measured by hours of incubation, navel score, embryo and chick weights, is accelerated by an exposure to light during incubation. There were no deleterious effects of exposure to light during incubation as measured by body weights at hatch, four weeks and eight weeks of age.

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Sixty Marston Broad White toms were used in each of two experiments (hatched February and late July) and were equally divided among six floor pens (1.5X2.4 m.). All birds were fed a commercial type starter diet through the tenth week of age. From the eleventh through the twenty-fourth week of age, one-half of the birds were fed a low protein grower diet (10.2 percent protein) while the remaining birds were fed the control grower (21 percent protein). Beginning with the twenty-fifth week all birds received a commercialtype breeder diet. At 30 weeks of age one male was placed in each of 18 female pens (ten females per pen).Body weights for the restricted males were 36-38 percent lighter than the controls at 24 weeks of age and changes in conformation were such that males fed the low protein grower diet could be ejaculated more easily than the controls. In general, the semen characteristics of the restricted males were also superior; however, this difference was non-significant. Fertility for the February hatched, naturally mated, birds was more than 100 percent higher for the males fed the low protein grower diet while fertile hatch was numerically, but not significantly, higher than the controls. Fertility and fertile hatch for the naturally mated, July hatch, birds were numerically, but not significantly, higher for the males fed the low protein grower diet. In the artificially inseminated birds, fertility and fertile hatch of the males fed the low protein grower diet were numerically, but not significantly, greater than the controls, in both experiments.It is obvious from these data that increased reproductive efficiency results from nutrient restriction of toms during the growing period.

Two experiments were conducted utilizing a total of 720 Marston Broadwhite females (hatched late December and July). The day old poults were equally divided among 18 floor pens and fed a turkey starter (27.8% protein) from 0-10 weeks of age. Onethird of the birds was assigned to each of the following feeding regimes: control grower (21% protein ad libitum), low protein (10.2% protein ad libitum), or skip-a-day (75% of control grower). All birds remained on these treatments through 24 weeks of age when the control group was placed on a commercial-type breeder diet (16.6% protein); six weeks later the remaining treatment groups were changed to this diet.Feed consumption and body weights were consistently greater for the control group. In all cases, regardless of season of the year or whether the birds were cage or floor reared, the age at sexual maturity was significantly delayed for the restricted birds as compared to the controls.Subsequent egg production tended to be greater in the restricted groups even when the initial two 28-day periods (while the two restricted groups were still on treatment) were included. Egg weight was not affected by treatment; however, it should be noted that the control group laid a much larger number of eggs that were considered too small for setting.It was concluded that nutrient restriction during the growing period is a highly effective method of delaying sexual maturity in the turkey breeder hen and, in addition, reduces production costs. It is hypothesized that any reasonable method of nutrient restriction will be effective if the program is designed to bring a hen to sexual maturity at a specific weight and age.

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