A growth monitoring system for monitoring growth of individual livestock animals having front legs and hind legs , such as cows, comprising - a barn environment in which one or more such livestock animals can move about, and which has a floor with bedding material , - a 3D camera with a downward looking field-of-view that comprises a part of the barn environment in which an individual one of the livestock animals may be present during a visit, and which 3D camera is arranged to obtain repeatedly a 3D image of said field-of-view, - an image processor arranged to process the obtained image, to extract a 3D point cloud representation of the field-of-view from said processed obtained image, - wherein the image processor is arranged to detect whether one of said livestock animals is present in said 3D point cloud representation, and - if yes, to select the animal part point cloud of said point cloud representation, and to determine a position dependent first height information, being a height (h1) above the floor of said animal part point cloud of said point cloud representation, and to determine a position of the front legs and/or the hind legs of said individual livestock animal from said animal part point cloud, - if no, to determine a position dependent second height information, being a height (h2) above the floor of said bedding material, wherein the image processor is arranged to determine a height of said individual livestock animal at said visit from said first height information, said second height information and said position of the front legs and/or of the hind legs. - a barn environment in which one or more such livestock animals can move about, and which has a floor with bedding material , - a 3D camera with a downward looking field-of-view that comprises a part of the barn environment in which an individual one of the livestock animals may be present during a visit, and which 3D camera is arranged to obtain repeatedly a 3D image of said field-of-view, - an image processor arranged to process the obtained image, to extract a 3D point cloud representation of the field-of-view from said processed obtained image, - wherein the image processor is arranged to detect whether one of said livestock animals is present in said 3D point cloud representation, and - if yes, to select the animal part point cloud of said point cloud representation, and to determine a position dependent first height information, being a height (h1) above the floor of said animal part point cloud of said point cloud representation, and to determine a position of the front legs and/or the hind legs of said individual livestock animal from said animal part point cloud, - if no, to determine a position dependent second height information, being a height (h2) above the floor of said bedding material, - if yes, to select the animal part point cloud of said point cloud representation, and to determine a position dependent first height information, being a height (h1) above the floor of said animal part point cloud of said point cloud representation, and to determine a position of the front legs and/or the hind legs of said individual livestock animal from said animal part point cloud, - if no, to determine a position dependent second height information, being a height (h2) above the floor of said bedding material, <EOS>