It is essential that we should now consider the feeding of the dairy cow: we have already indicated that the lactation curve will respond to controlled feeding and that this will increase the overall production of the cow.
For milking cows, the current daily yield has normally been used to decide the food requirements of the animal, in addition to the maintenance allowance, that is the requirement for production of milk, and it has to be looked at retrospectively. This means that we would look at yesterday’s or last week’s total production to decide what to feed the animal for the next week. The tables below have been included for your benefit, in order to determine what to feed dairy animals.
The first thing you must remember when feeding animals is that you have to satisfy the maintenance requirement first, and then the production requirements.
Look at Table 1 for an example:
Take a 500kg mature cow. What will she require for 20kg of 4.0% fat milk a day?
- Dry Matter per day 3/100 x 500 = 15kg
A good rule of thumb is that the Dry Matter requirements of an animal are approximately equal to 3% of its live-mass.
- Crude Protein: 0.638kg/day
- Total Digestible Nutrient – 3.7kg/day.
These represent the Maintenance requirements, and to this we must add the production requirements per kg of milk produced. At the same time we must know the % fat and the production.
· At 4.0% Fat, C.P. = 0.078 kg x 20kg = 1.56kg C.P.
· At 4.0% Fat T.D.N. = 0.330 x 20kg = 6.6kg T.D.N.
Therefore Total requirements are as follows:
- Dry Matter = 15kg/day
- Crude Protein
- Maintenance = 0.638kg/day
- Production = 1.560kg/day
- Crude Protein
Total Digestible Nutrient
- Maintenance = 3.70kg/day
- Production = 6.60kg/day
· Total = 10.30kg/day
Thus you can see how to calculate the nutrient requirements of dairy cattle.
Table 1: Daily nutrient Requirements of lactating Diary Cattle: Maintenance Requirements
|Body Mass kg||Crude Protein (kg)||Digestible protein (kg)||Net energy lactating cows (Meal)||Total digestible nutrients (kg)||Ca (g)||P (g)|
Table 2: Milk Production (Nutrients required per kg milk up to 20kg/day milk yield)
|Percent Fat||Cp (kg)||DP (kg)||NE lact. Cow (meal)||TDN (kg)||Ca (g)||P (g)|
Source: Donkin, E.F. (1976)
According to Donkin, both protein (C.P.) and energy (T.D.N.) must be carefully supplied in the concentrate form otherwise one or the other will be wasted or used less efficiently. Although some research has indicated that slight deficiencies of protein can be partially compensated for by increasing the allowance of energy, the above requirements are the best estimate available of what a cow needs. If one nutrient is in slight excess, it should be energy rather than protein because energy foods are cheaper than protein. Mineral and Vitamin requirements must also be fully balanced.
The following is a carefully worked out series of examples which you should study fully. Although the prices are not up to date, it should serve as an illustration on how to work out the rate of feeding concentrates.
RATES OF FEEDING CONCENTRATES
Concentrates have more nutrients per kilogram than roughages. Rate of feeding will depend upon the capacity of the cow regarding its requirements. Cows are often fed meal at fixed rates, for example, 0.4kg/kg milk (equivalent to 4kg/10kg milk). If we choose a rate of feeding, what sort of concentrate will we have to feed, to supply the nutrients? For the following example, the requirements are tabled for 3.5% butterfat milk.
Table 3: Recommended Composition of Dairy Meals Fed at Different Rates
|Rate of Feeding kg/kg milk||Crude Protein % *||Total Digestible Nutrients % **|
COMMERCIAL DAIRY MEALS
Various types of meal which aim to supply all nutrients for milk production are available. As feed companies are not required to declare energy content of dairy feeds, calculations of relative values must be made in terms of protein – assuming energy to be adequate. Prices have risen considerably over the last few years, and will continue to rise, but any new situation can be assessed using certain basic principles. The examples used here will be based on chemical analyses; these can give guidance.
In the following examples, assumptions are made on analysis and price of meals. These merely illustrate the principles involved and are in no way intended to refer to any product commercially available.
Three dairy meals are available, containing 12%, 15% and 18.5% CP. Their respective prices/ton are
$180, $210 and $280. Which is the best value? If their prices change to $200, $250 and $300/ton respectively, which is the best value?
|CP (%)||Cost/t ($)||Cost/kg Feed (c)||Cost/kg CP||Rate of feeding (kg/kg milk)||Cost/kg Milk (c)|
The initial situation shows that the 15% CP meal would be marginally cheaper; meal that is cheapest per ton is not necessarily the best value.
However, at the adjusted prices, the other two would be cheaper; even though the 15% CP meal would be the same price per CP as the 12% CP meal. It would cost 0.5c more to produce 1kg milk.
MIXING ON THE FARM
Assuming there is an abundant supply of maize on the farm, does it pay to mix feed for dairy cows? Again, the answer depends upon relative prices. Maize should be costed at selling price less transport costs, plus milling cost. These will vary as will transport costs of feed from the depot. Various dairy premixes are available from stock-feed companies for farmers to mix with their own maize. The feed representative from the company must advise the farmer.
The input values can be adjusted according to the particular situations on each farm, and the price of the best mix compared with the cost of buying a dairy meal. On some farms, the saving may be so small as to not be worth the bother; on others, it may be significant and justify the extra inputs of organisation, labour, equipment and storage space.
- The best dairy meal is the one which supplies, at lowest cost, all the nutrients required by lactating cows;
- It is important that roughage should be balanced and adequate. Only then can a dairy meal justifiably be fed according to milk production;
- Rate of concentrate feeding according to milk production will depend on the analysis of the meal. Cost per kilogram of milk produced is the best means of comparing different meals. Total food eaten may be a limiting factor in production from bulky feeds and;
- Home-mixed dairy meals may be cheaper than bought feeds. The actual saving will differ from farm to farm, and must be measured after extra labour, capital and inconvenience have all been taken into consideration.