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The aim of this research was to evaluate the effect of the modification of diet starch content on milk composition and on<br />its nitrogen and mineral fractions. Ten Italian Friesian primiparous cows were randomly assigned to two groups and fed<br />a basal total mixed ration, (BSD, basal starch diet, 24.9% starch/DM) until 42 days in milking (DIM). At 43 DIM, 5 animals<br />(control group, CTR) continued to receive the same ration and the remaining 5 cows (experimental group, EXP)<br />were fed a low starch diet (LSD, 21.0% starch/DM) until 65 DIM, followed by a high starch diet (HSD, 28.3% starch/DM)<br />66 to 85 DIM. From 86 DIM until 94 DIM, cows of the EXP group returned to the BSD. Milk samples were collected at 37,<br />50, 60, 70, 80, 94 DIM. Starch intake was lower for EXP at DIM 50, 60 and higher at 70 and 80 DIM (P < 0.01). Milk<br />yield and fat corrected milk (FCM) did not vary between groups and times of sampling, but HSD caused a significant (P<br />< 0.05) reduction of milk fat in the EXP animals. NPN and MUN contents were affected by dietary treatments at 80 DIM<br />(P < 0.05), being higher in CTR and lower in EXP group in comparison to their basal values (37 DIM). The &alpha;s1-casein<br />percentages at 80 and 94 DIM increased in the EXP but not in the CTR group, and a marked decrease of &alpha;s2-casein percentage<br />for the EXP group at 94 DIM was observed (P < 0.05). Milk sodium content decreased at 80 and 94 DIM and the<br />sodium to potassium ratio was reduced after the return to the basal diet in the EXP group (94 DIM), indicating that dietary<br />starch variations can be involved in the control of epithelium integrity of mammary gland in early lactation.