Effects of replacing alfalfa hay and corn silage with corn straw in diets on milk production and composition of dairy cows
A study was conducted to determine the effects of replacing alfalfa hay and corn silage as the only forage source with corn straw on milk production and composition. Thirty-two primiparous Holstein cows (55±15 d, days in milk) were divided into 2 groups fed ad libitum a TMR containing either 17.30% alfalfa hay and 18.77% corn silage (control group) or 36.07% corn straw (CS group). The experiment period was 105 d with 14 d adaptation. Cows were fed individually with auto feeding system and food intake was recorded continuously using a computerized monitoring system (RIC system, Insentec B.V., Marknesse, the Netherlands). Data were analyzed using the MIXED procedure of SAS (SAS 8.2; SAS Institute Inc., Cary, NC). Dry matter intake (21.35 vs. 17.43 kg/d, P<0.01), crude protein intake (3.84 vs. 2.90 kg/d, P<0.01) and consumption rate (103.25 vs. 68.65 g DM/min) were higher in the control cows, indicating more attractiveness to the cows. Higher milk yield (30.45 vs. 23.12 kg/d, P<0.01), milk protein content (3.66 VS. 3.32 %, P<0.01) and yield (1.11 VS. 0.77 kg/d, P<0.01), milk fat yield (1.34 vs. 1.02 kg/d, P<0.01), milk lactose yield (1.47 vs. 1.13 kg/d, P<0.01) were observed in the control cows, whereas milk fat content (4.46 vs. 4.38 %, P=0.65), and milk lactose content (4.86 vs. 4.80 %, P=0.09) were similar in the 2 groups. Feed efficiency (1.45 vs. 1.32 %, P<0.01), and milk N efficiency (29.68 vs. 26.67 %, P<0.01) were higher for control group compared with CS group. In conclusion, replacing alfalfa hay and corn silage with corn straw decreased milk production, and affected milk composition.
Keywords: milk composition, forage, dairy cow