SELF-SELECTION OF LEAD SUPPLEMENTED DIETS BY CHICKS .3. EFFECT OF AGE

In the present experiment the self-selection of lead supplemented diet s starting from day 1, 14 and 28 of age to the day 53 of age was exami ned using a non-supplemented control group, a choice group and a lead supplemented group. The lead supplement was 1,800 ppm Pb as leadcarbon at in the feed. The weight of each chicken was measured once a week an d the feed intake twice a week, each half of the through separately. T he preference value was determined by the percentage intake of the con trol feed of the entire feed intake. The preference value was tested u sing the 50%-mark as basic hypothesis. The supplement of 1,800 ppm Pb in the feed from the day 1, 14 and 28 of age resulted in a significant lower weight gain compared with the non-supplemented control group. T he choice group starting at the age of 28 days prefered the non-supple mented feed with a preference value of 64%. The group starting with th e choice feeding at the age of day 1 did not show any feed selection, the preference value was 53% and the fattening results were 10% less t han those of the control group. Also the choice group starting at the age of 14 days did not develop a feed selection, but was able to gain the same fattening results as the control group. The clear feed select ion of the choice group starting at the age of 28 days was explained t o depend on the greater experience in the environment and on the less lead toxicity after the feed intake.