The aim of this study was to evaluate the effect of different levels of canola oil or/and fish oil supplementation on dry matter intake (DMI), and milk production and composition in early lactating Holstein dairy cows. Eight multiparous early lactation Holstein cows (42±12 DIM, 40±6 kg daily milk yield) were fed a total mixed ration supplemented with either 0% oil (Control), 2% canola oil (CO), 2% fish oil (FO), or 1% canola oil + 1% fish oil (CoFo), according to a double 4 × 4 Latin square design. Each period lasted 3 wk; experimental analyses were restricted to the last week of each period. Diets were formulated to be isonitrogenous using NRC 2001. Cows were housed in tie stalls and fed the TMR two times a day to allow 5 to 10% orts (as-fed basis). Cows were milked 3 times per day and yields were recorded. Milk samples were collected from each milking on 1 d per wk and composited for analysis of fat, protein, and lactose. Data were analyzed as a replicated 4 × 4 Latin square using the GLM procedure of SAS (2001). The model included effects caused by diet, period, and cow. Least squares means are reported throughout, and significance was declared at P < 0.05. Diet had no effect on DMI (24.92, 25.60, 23.70, and 25.84 ± 0.79 kg/d; for control,CO, FO, and CoFo, respectively). Milk production was similar among the groups (34.41, 34.15, 32.93, and 34.55 ± 0.84 kg/d, respectively). Milk fat content (2.87, 2.70, 2.45, and 2.89 ± 0.21%, respectively), milk protein content (2.88, 2.86,2.92, and 2.89 ± 0.07%, respectively), and milk lactose content were all similar among the diets. The results of this study demonstrated that the canola oil or/and fish oil supplementation in the diet of early lactation cows had no apparent effect on the DMI, and milk production and composition.

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