Growth and behavior of newly hatched chicks with and without yolk sacs

This experiment was designed to study effects of feed sources differing in energy and protein levels as well as yolk removal on behavior, body weight, and gastrointestinal tract (GIT) growth and contents in male chicks from a commercial white egg-layer stock. Yolk sacs were surgically removed (YR) from half of the chicks while the other half remained yolk-intact (YI). From Days 0 to 6, all chicks were offered a choice of residual yolk (Diet Y) or mash (Diet A) and beginning on Day 6, all chicks were fed Diet A. Throughout the experiment, the YI chicks were heavier than YR chicks, but by Day 13, the YR chicks gained proportionately more body weight. The only difference in GIT data was the weight of chyme at 21 days of age, which was higher in the YI chicks than in YR chicks. Behavior results showed that YI chicks stood more while YR chicks rested more throughout the experiment. Experiment 2 consisted of 4 groups: YI chicks fed Diet E (mash feed higher in energy and protein), YI chicks fed Diet A (mash feed lower in energy and protein), YR chicks fed Diet E, and YR chicks fed Diet A. Dissections on Days 6, 13, and 20 quantified effects of diet and/or treatment on growth and contents of GIT segments. On Days 13 and 20, there were no differences due to diet of treatment for GTT data except for the consistent difference due to diet for relative weight of the gizzard, with a higher value in the Diet A chicks. Similar to results from Experiment 1, on Day 13 YR chicks gained relatively more body weight than YI chicks fed Diet A. Also consistent with Experiment 1, of chicks fed Diet A, the YI chicks stood more than the YR chicks.