The aim of this study was to determine the effects of dry period length (35 vs. 20 days) and dietary strategy (lipogenic vs. glucogenic diet) on dry matter intake (DMI), milk production and milk composition in early lactating Holstein cows using a 2x2 factorial arrangement. 1Wenty-four Holstein dairy cows were housed individually and allocated to 4 experimental treatments: G35: a glucogenic diet with a 35-d dry period; L35: a lipogenic diet with a 35-d dry period; G20: a glucogenic diet with a 20-d dry period and L20: a lipogenic diet with a 20-d dry period. Dry matter intake was recorded daily until8 week postpartum. After parturition, cows were milked 3 times per day at 04h00, 12h00 and 20h00. Milk yield was recorded and milk was sampled during 8 weeks postpartum. Data were statistically analyzed using MIXED procedure of SAS. No significant difference was obseiVed in prepartum and postpartum DMI among treatments. A significant difference (P<0.05) was found between treatments G35 and G20 regarding milk production and daily yields oflactose, milk protein and milk solids non-fat (38.4 vs. 30.6, 1.79 vs. 1.43, 1.19 vs. 0.96 and 3.29 vs. 2.63 kgld, for G35 and G20, respectively). Milk fat concentration for G35 was significantly (P<O .05) lower than for L35 (3 .66 vs. 4.08% ). Week of lactation had a significant (P<O.O 1) effect on DMI,milk production and milk composition. These results suggest that the mammary gland would require a dry period length of more than 20 days to allow a high milk secretion.

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