Dietary conjugated linoleic acid (c9,t11/t10,c12-CLA), but not various dietary trans-18:1 fatty acids, increases mammary gland branch point number in ovariectomized mice. Mice were ovariectomized at 21 days and fed the either the control diet (TFA-CON) or that with 5% fat as partially hydrogenated linseed oil (PH-LIN), PH-SAF, partially hydrogenated sunflower oil (PH-SUN), or 2.7% conjugated linoleic acids (c9,t11/t10,c12-CLA) from 22 days of age until euthanasia at 42 days of age. a Mammary ductal area was measured using ImageJ. b Mammary gland branch point number was measured using AngioTool. c Branchpoint density was branchpoint number normalized to ductal area. Data are mean ± SEM (n = 6–8/diet). a, bMeans with different letters are different (P < 0.05)