Source: University of Guelph
Dairy cow feed rations are formulated by determining the animal’s total DMI, nutrient requirements, and the amount of feeds available on farm that must be fed to fulfill said requirements.
The total DMI varies depending on the animal. Variables affecting total DMI are: weight of animal, requirements above maintenance, age, days in milk, and days pregnant. Nutrient Requirements are met by optimizing roughages first, then grains and supplements are added in the balance requirements. The amount of available feed must be determined in order to ensure nutrient requirements are met, as not all of the nutrients from DMI are directly available to the cow.
Water Intake
| Maintenance Requirement (Dry Cow) | Lactating Cow |
| 40 L/day | Water:milk ~ 3:1 |
Dry Matter Intake (DMI)
|
Type of DMI |
Dry Cow |
Lactating Cow |
| Forage DMI | Approx. 2% of BW | – Approx. 2% of BW (1.8 – 2.2)
– Approx. 0.9 – 1.0% of BW as NDF (forages only) |
| Total DMI | Approx. 2% of BW | – Typically 3.5 – 4 % of BW
– Approx. 1.2% of BW as NDF (total ration) – Can be a 20% decrease in fresh cows (< 1 month) |
Fiber
| ADF | No less than 19% of the total ration |
| NDF | – 25 – 28% of the total ration (up to 30% for fresh cows)
– 75% of ration NDF should be from forage |
Protein
| CP | Typically between 16 – 18% |
| DIP | No more than 67% of CP |
| UIP | At least 33% of CP |
Minerals/Vitamins
| Ca | 0.7% of ration DM |
| P | 0.3% of ration DM |
| Mg | 0.3 – 0.4% of ration DM |
| K | 1 % of ration DM |
| Se | Approx. 7 mg/day or 0.3 ppm of ration DM |
| Vit E | 1000 to 3000 IU/day of ration DM (higher for transition cows) |
Other trace minerals are approx. 50 – 150% of NRC
Lipids
- 4 – 6% of total ration (levels above this will decrease DMI)
Energy
- Not technically a nutrient but still a requirement
- No more than 0.8 Mcal/day deficit
Dietary Cation-Anion Balance
|
Production Level |
DCAB range |
| Lactating Cows | 250 – 350 mEg/kg |
| Dry Cows | -100 – 0 mEg/kg to prevent milk fever |
Other things to consider
- Ideal forage is approx. 20% CP, 30% ADF, and 40% NDF
- Total Ration Dry Matter (for a TMR) is approx. 50% (between 40 – 60%)
- Forage to Concentrate Ration (F:C)
- Dry cows and growing heifers can be 100% Forage
- Lactating rations are typically between 40:60 and 60:40
- Should not be less than 40% forage unless the level of management is very high
References:
Dairy Nutrition Primer Notes, Dr. Lissemore (2015)
Dairy Nutrition Elective, Ration Thumb Rates, Dr. Lissemore (2015)
