Effects of dietary crude protein, electrolyte balance, and photoperiod on growth of broiler chickens.

Three experiments were conducted with broiler chicks to study the effects of dietary electrolyte balance, dietary crude protein level, and photoperiod on performance. Increasing the electrolyte balance (Na + K -Cl) from about 200 meq/kg to 350 meq/kg or more improved gain and feed consumption of chicks fed high protein (28.6%) diets but depressed gain and feed consumption of chicks fed low protein (14.3%) diets. Neither sex nor photoperiod affected to nature or magnitude of the crude protein X electrolyte balance interaction, although birds housed under 16L:8D had significantly higher concentrations of plasma ammonia than did those housed under 23L:1D. Chicks fed diets containing a high vs. a low electrolyte balance had significantly higher concentrations of plasma uric acid and significantly lower kidney asparaginase activities. Electrolyte effects on kidney asparaginase activity were not affected by diet crude protein content. Results indicate that the electrolyte balance that provides for optimum growth is dependent upon dietary crude protein concentration. Further, diet electrolyte effects on metabolic acid-base homeostasis are not related to their effects on growth.

The effect of light regime on growth and pattern of body fat accretion of broiler chickens.

A seven week serial slaughter experiment was conducted with male and female broiler chickens to determine the effect of photoperiod on body growth rate and pattern and rate of fat deposition. The two light regimes compared were constant light and a 16 hour light:8 hour dark photoperiod. Males grown under the 16L:8D photoperiod consumed less feed and grew less rapidly than males under constant light. The slower rate of growth was apparently due entirely to less feed consumption, since feed efficiency of males was unaffected by light treatment. Females reared under 16L:8D also grew less rapidly than under constant light. However, the difference was much more pronounced than in males, and was not due to reduced feed consumption, rather to less efficient feed utilization. Females grown under 16L.8D exhibited a slower rate of increase in percent daily fat gain than did females grown under constant light. At seven weeks of age, total body fat content of females averaged 12% less when grown under 16L:8D. Rat and pattern of fat gain in males was unaffected by light treatment. The incidence of leg abnormalities was substantially lower for both sexes reared under 16L:8D.