Effect of different Roughage: Concentrate Ratio on Milk Yield and Its Fatty Acid Profile in Dairy Cows

Abstract

Experiment was conducted on eighteen crossbred dairy cows divided into three groups of six animals in each group. Cows were fed on roughage (berseem hay, green sorghum forage and wheat straw) and concentrate. The ratio of roughage: concentrate varied in the three treatment groups from 50:50 (T₁); 60:40 (T₂); and 70:30 (T₃). DMI decreased with increasing the level of roughage in the diet. Digestibility of DM, CP, EE, NFE, and OM showed a significant decrease (P <0.05) when R:C was increased. NDF digestibility did not vary between treatment groups. On the other hand, CF and ADF digestibility were significantly (P <0.05) decreased with decreasing R:C. Increasing R:C significantly (P <0.05) decreased milk production, but production of 4% FCM was not affected by forge level. Milk fat concentration was significantly (P <0.05) decreased by 6.30 and 3.78 % in T₁ and T₂, respectively, as compared T_3. Increasing R:C had non significant effect on milk lactose, CP, TS, SNF, MUN, Ca and P level. Milk cholesterol level in T₃ was lowered by 13.35 and 8.27% as compared to T₁ and T₂, respectively. The concentrations of TLCFA, TUFA, MUFA and PUFA were increased with the increase in roughage level in the diet, whereas, TSFA level was reduced. PUFA content of milk fat (g/100g fat) was increased by 141.75% in T₃ over T₁. Total CLA production (mg/g fat) in T₃ was increased by 50.92% over T₁. Total feeding cost decreased as the level of roughage in the ration increased. Total feeding cost decreased as the level of roughage in the ration increased. Feeding cost of T₃ per g PUFA production reduced by 68% and 48% as compared to T₁ and T₂, respectively. Feeding cost of T₃ per g CLA production was reduced by 47% as compared to T₁. The feed cost per kg milk, per g PUFA and CLA production was lowest for the cows fed 70:30 roughage: concentrate ratio diet.  In summary, these results suggest that cows producing 12-14kg of milk/d could be best maintained on a dietary regimen of 70% good quality roughage and 30% concentrate to have the maximum production of human health beneficial conjugated linoleic acid without compromising on milk yield.

Keywords: Dairy cow, concentrate, roughage, milk fatty acid, conjugated linoleic acid