Formulating the correct rations for your dairy cows is critical to their health and production, writes Stephan Gericke, ruminant technical advisor at Meadow Feeds. He gives us insight into what to look for when formulating dairy cow rations.
In pasture-based systems, cows are fed a ration in the milking parlour twice a day while being milked. Before and after milking, the cows normally graze pastures or are fed other preserved feedstuffs, such as maize silage.
The important question to ask when formulating a dairy cow ration is “what is the goal of the ration?”. What do you want to achieve by feeding this ration?
When formulating a ration, one aims to balance the total diet by designing a supplement that is complimentary to the feedstuffs available on the farm. It is thus very important that an accurate assertion of the quality and quantity of the farm feedstuffs are established.
Feed samples should be taken on a routine basis and analysed in a laboratory to establish the nutrient profile of the feedstuff. The composition of the dairy ration will differ upon the type, quality, and quantity of the feedstuffs used. Ultimately, the ration should supply the needed nutrients so that the cow may reach its full genetic potential. The most important consideration when formulating a dairy cow ration is that it should always be aimed at increasing the farm’s profit.
What are nutrients?
Nutrients are the chemical substances within an ingredient or raw material that gets used by the animal to survive, grow, produce and reproduce. Nutrients are divided into two categories, which are macronutrients and micronutrients. Macronutrients are required by the body in large amounts, and micronutrients are required by the body in small amounts.
In general, these nutrients can be classified in terms of protein, non-fibre carbohydrates, fats, fibre, minerals, and vitamins. In the gastrointestinal tract of the animal, these nutrients are further broken down into smaller fractions which are then taken up and utilised by the cells of the animal.
A shortage of a certain type of nutrient can prevent the animal from achieving a specific result. In the winter, for example, when pasture production is low, cows will normally receive maize silage as a means to maintain their dry matter intake. If the cows are only receiving maize silage, they will experience a drop in their milk production mainly due to a shortage of protein supply. Protein is critical in the production of milk.
It is also possible that one nutrient can be in an oversupply. In spring, for instance, when the newly planted pastures are ready to be grazed, it is very high in protein and can therefore lead to an oversupply of protein which will cause a reduction in milk production. This is due to the protein having to be broken down and excreted. The oversupply can also cause possible fertility problems. There are other, similar scenarios for an over or undersupply of energy, minerals, and vitamins.
Minimum and maximum nutrient specifications for the desired ration
Feed nutritionists use formulation or modeling programs to help them formulate animal rations. These programs require input from the nutritionist. Formulating a ration starts by collecting data and inputting the data into the modeling program. These inputs include, but are not limited, to the following:
| Animal inputs: | Farm inputs: |
| Type (breed) of the animal | Temperature and humidity |
| Weight of the animal | Daily walking distance |
| Days in milk | Vertical height of the slope |
| Milk production in litres | Quantity of pasture/feedstuff intake and availability |
| Milk quality (butterfat and protein percentages) | Quality of the pasture/feedstuffs being fed |
| Body condition score of the animal | Housing/paddock facility (cleanliness, comfort) |
Based on these inputs, the program will then generate the minimum and maximum nutrient requirements. Let’s look at some of the main macronutrients when formulating dairy cow diets:
Protein
The three main components of protein to look at when formulating ruminant diets, are rumen degradable protein, limiting amino acids (methionine, lysine, histidine, and phenylalanine), and rumen undegradable protein.
- Rumen degradable protein is needed to supply nitrogen to the rumen to support microbial growth and should range between 9.5 to 11%. Lower dry matter intake levels may warrant lower rumen degradable protein levels and levels above 11% will typically lead to low nitrogen efficiency and higher nitrogen losses through urine.
- Metabolizable amino acids drive animal performance from the protein side. The four most limiting amino acids in dairy cow nutrition are methionine, lysine, histidine, and phenylalanine. These can be supplied through microbial protein as well as through rumen undegradable protein.
- Rumen undegradable protein passes through the rumen unchanged and some of it can be digested in the small intestine. It complements the microbial protein that is produced and is necessary for cows producing at higher levels of production. It should range between 4 to 6,5%, depending on the level of production.
Fibre
The two main components of fibre are digestible neutral detergent fibre (NDF) and effective NDF.
- Digestible NDF is the fibre component that provides energy to the cow and should range between 17 to 20% in pasture herds. Higher digestible NDF levels will correspond to lower starch levels.
- Effective NDF is a measure of the effective NDF content of the diet that is needed for rumen mat formation. The minimum should be 22%. Diets below 22% are more likely to experience acidosis problems and/or higher passage rates.
Non-fibre carbohydrates
The two most important components of non-fibre carbohydrates are starches (total and rumen digestible starch) and sugars.
- Total starch is a key energy source in most dairy diets and total starch should be between 14 to 18% of the total diet in pasture herds. Starch levels can be lower if a significant portion is coming from readily fermentable sources.
- Rumen digestible starch drives rumen fermentation and microbial protein creation and should range between 15 to 19%.
- Sugar supplies a rapidly available source of carbohydrate for the rumen microbes and should be between 4 to 8.5%. The risk of problems occurring in the rumen is higher at sugar levels above 8.5%.
Fat
The most important component of fat is the unsaturated fat level of the diet.
- High levels of unsaturated fat in the diet are more likely to cause milk fat depression issues and negatively impact NDF digestibility. It should range between 2.5 to 3.5%.
We have already touched on the nutrient topic, but before we get to the third aspect of cow rationing, we need to understand that there is a difference between an ingredient and a nutrient. A nutrient is the building block that the animal needs for survival, growth, and performance. An ingredient refers to a single raw material used in combination with other raw materials to make a ration. In other words, it is the building blocks of a ration.
A single ingredient contains hundreds of nutrients, and the nutrient profile will differ for each type of ingredient. The main ingredients are maize, soya beans, sunflower seeds, wheat, and their by-products, as well as feedstuffs that are being fed on the farm.
What ingredients are available, in what quantities, and at what price?
After setting the nutrient minimums and maximums, the formulation program will then choose a mixture of ingredients so that all the nutrient requirements are met. Today, there are many feed formulation programmes available and most are based on a least-cost formulating system.
The least-cost system will ensure that the ration is compiled of the most cost-effective ingredients (based on their nutrient specifications, availability, and price) in order to give a ration that is well priced, and able to meet the required nutrient specifications , and achieve the desired outcomes. Bear in mind that not all formulation models are created equal, that the nutritionist should be able to trust that the nutrient requirements set by the model are accurate and that the predicted performance should reflect the true nature of the animal as best as possible.
The challenge when formulating pasture-based dairy cow rations is that the cows normally only consume a third of their total diet inside the milking parlour from bought-in feeds. Therefore, the ration should be supplementary to the on-farm feeds, while providing all the necessary nutrients to enhance the cow’s performance.
- For more information on the subject or the nearest Meadow Feeds technical advisor to your area, simply click here.
ALSO READ: Meadow Feeds: Celebrating 80 years in animal nutrition
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