Dam Variance Research Articles

The Heritability of the Percent Gamma Globulin Level in the New Hampshire Chick

The percent gamma globulin levels obtained at hatch, 1, 3, 5 and 7 weeks of age were 12.4, 10.9, 11.5, 14.2 and 15.4 respectively. Only weeks 1 and 3 were not significantly different. The decrease from hatch to 1 week of age was attributed to a loss of maternal antibody and a low rate of synthesis by the chick. The greatest increment from 3 to 5 weeks of age was consistent with the reports in the literature.The within individuals, variance component, obtained from the analysis of each age group considerably increased from 1 to 7 weeks of age. The sire and dam variance components did not vary with time.A large maternal effect at hatch was suggested by the sire (hs2=0.17) and dam (hd2=1.21) estimates of heritability. The analysis of the data from 1 to 7 weeks of age gave a sire estimate of heritability of 0.26 and a dam estimate of 0.67.

The Number of Daughter-Dam Pairs Needed for Estimating Heritability

A formula for estimating the number of daughter-dam pairs needed when estimating heritability by daughter on dam regression in the one-way classification analysis for fixed values of the average number of pairs per class, of the ratio of daughter to dam variance, of the anticipated heritability estimate, and of the desired variance of the estimate has been presented. The effect on N of changes in these four variables has been illustrated. This procedure was extended to multiple classification analysis and was also used to determine the number of pairs needed to estimate repeatability by regression of second records on first records.