Routinely, genetic evaluations are based on 305-d lactations, which represent the size or magnitude of lactation curve but ignore the shape, an inherently multidimensional feature. We combined the methods of quantitative genetics and the geometric morphometrics (GM) to evaluate the heritability and genetic correlations of size and shape of lactation curves. The data were daily records of first parity milk production from January 2014 through January 2017 from 43 communal herds distributed throughout Israel. We proposed 2 geometrical shapes of lactation curves, one depicted by line graph and the other by orbital graph; using monthly records as the basis for estimating landmark coordinates, superimposition, and genetic evaluation. Lactation curve shapes were represented by a set of 2-dimensional coordinates. These landmarks were then superimposed using the Procrustes technique to extract shape information. The size of the line- and orbital-depicted lactation curve was recorded as the centroid size (CS), computed as the square root of the summed squared distances of each landmark from the centroid. Heritabilities and genetic and environmental correlations computed by the MTC REML individual animal model program for CS of the proposed shapes and total lactation are in Table 1. Similar heritability values and complete genetic and environmental correlations of the CS of the orbital lactation curve with the traditional method validate it as proxy for the size measure of lactation curves. The heritability of shape was 0.179 for the orbital-depicted lactation curve and 0.082 for the line-depicted lactation curve. These results demonstrate GM as a promising new approach to study the patterns of phenotypic and genetic variation of shape and size of lactation curve in dairy cattle. Table 1. Heritabilities (on the diagonal) and genetic (above diagonal) and environmental (below diagonal) correlations of centroid size (CS) and total lactation among 3,492 first-parity cows¹

Variable	CS-line	CS-orbital	Total lactation
CS-line	0.09	0.49	0.48
CS-orbital	0.02	0.39	1.00
Total lactation	0.02	1.00	0.39

¹Standard errors of heritabilities were <0.05.