Performance and physiological profiles of high dietary zinc and fasting as methods of inducing a forced rest: a direct comparison.
Equal periods of fasting or high zinc feeding as a means of inducing a forced rest were examined. Single Comb White Leghorn hens (60 weeks of age) were fasted (F) or fed a layer diet containing 20,000 ppm zinc (Zn) for either 4 or 10 days in a 2 X 2 factorial arrangement of treatments. Feed intake was markedly depressed in the first day of high zinc feeding and averaged 10.7 and 6.1 g/hen-day during the 4 or 10 days of Zn feeding. Body weight losses of hens fasted or fed high dietary zinc were not significantly different. Egg production rate was highest for hens treated 10 days (both F and Zn) in the immediate weeks following the rest. However, over the entire 6-month experimental period, there were no significant differences among the four treatments. Ovary and oviduct regressed similarly in F and Zn hens. Tissue zinc concentration greatly increased during zinc feeding, especially in the pancreas, and rapidly returned to normal upon refeeding a normal layer diet. Fasting also caused a substantial increase in tissue zinc. The results show that the effectiveness of zinc as a forced-resting agent for hens is related to changes in feed intake.
McCormick
C C
CC
Department of Poultry and Avian Sciences, Cornell University, Ithaca, New York 14853.
Cunningham
D L
DL
D000818:Animals; D002645:Chickens / Q000502:physiology*; D004032:Diet; D005215:Fasting; D005260:Female; D009929:Organ Size / Q000187:drug effects; D010053:Ovary / Q000187:drug effects; D010057:Oviducts / Q000187:drug effects; D010058:Oviposition / Q000187:drug effects*; D012146:Rest; D015032:Zinc / Q000378:metabolism / Q000494:pharmacology*
D015032:Zinc