- RATIONS FOR MILK PRODUCTION (continued)
In the last lecture you were shown how to make up a ration for production of milk of 4% butterfat This was a simple ration for milk production using two ingredients; maize meal and groundnut cake.
It is possible to buy ready-mixed rations for milk production from Livestock Feed Firms that are priced and sold according to the Protein content of the food. How do we know what Protein and
T.D.N. are required in a ration which is balanced for milk production? We know the requirements for milk production, and we know that the meal will be fed at 0,5kg for each 1kg of milk.
The calculation is as follows:
Required for 1kg of milk of 4% butterfat:
- T.D.N. – 0.33kg
- D.C.P. – 0.051kg
The percentage D.C.P. required in a mixture to be fed at 0,5kg per 1kg of milk would be:
- 0.051 x 100 / 0.5
= 10.2 or 16% D.C.P.
T.D.N. requirement would be:
- 0.33 x 100 ¸/ 0.5
= 66% T.D.N.
The calcium requirement would be:
- 0.0027 x 100 ¸/ 0.5
= 0.54% calcium
The phosphorus requirement would be:
- 0.002 x 100 ¸/ 0.5
= 0.4% phosphorus
A meal that is balanced for milk production would have a composition of:
- T.D.N. – 66%
- D.C.P. – 10%
- Ca – 0.54%
- P – 0.4%
and would be fed at 0.5kg per 1kg of milk. The important factor in these meals is the protein percentage. D.C.P. of 10% is equivalent to a crude protein level of 14.5% e.g.
- (14.5 x 0.9) – 3 = 13,05 – 3 = 10%
If you wanted a meal to feed at the rate of 0,6kg per 1kg of milk it would need to have a D.C.P. of:
- 0.051 x 100 ¸/ 0.6 = 5.1/0.6 = 51/6 = 8.5% or a CP of 13%
A meal fed at 0.4kg per 1kg of milk would need:
- 0.051 x 100/ 0.4 = 5/0.4.1 = 51/4 = 12.75% D.C.P. or 17.0 % C.P.
If you were feeding a herd of Jersey cows producing milk with a butterfat content of 5%, the meal to be fed at 0.5kg per 1kg of milk produced would require:
- 0.056 x 100 ¸/ 0.5 = 5.6/0.5 = 56/5 = 11.2% D.C.P.
2. CALCULATING A PRODUCTION RATION USING PROTEIN ONLY
We know the D.C.P. required for a dairy meal to be fed at 0,5kg per 1kg of milk is 10%. When working out a simple production ration using maize as the main ingredient we can find out the amount of the other ingredient required by using the method called Pearson’s Square. Going back to the example in the last lesson, we had maize with a D.C.P. of 6.5%, and groundnut cake with a D.C.P of 37%. The D.C.P in the final mixture is 10% and we put these figures into the square as follows:
Take 6.5 away from 10 and 10 away from 37 and complete the square.
Divide 27 by 3.5 and this gives 7.7. Consider the first number only. The ratio we want is 7 parts of maize to 1 part of groundnut cake or 70kg of maize to 10kg of groundnut cake.
As another example we will use maize (D.C.P. 6.5) and cottonseed with a D.C.P. of 17:
The ratio is 2:1 and this means 2 parts of maize and 1 part of cottonseed. We can check this as follows:
| Maize | T.D.N. 80 | D.C.P. 6.5 |
| Cottonseed | T.D.N. 90 | D.C.P. 17 |
| T.D.N. | D.C.P. | |
| 20kg of Maize will give: | 80/100 x 20 = 16kg | 6.5 x 20 = 1.30kg |
| 10kg of cottonseed will give: | 90/100 x 10 = 9kg 100 | 17/100 x 10 = 1.7kg |
| TOTAL | 25kg | 3.0kg |
| 30kg of mixture will give | 25 kg of T.D.N. and 3.0 kg of D.C.P. | |
| 1kg of mixture will give | 25/30 = 0.83kg of T.D.N. and | |
| 3.0/30 = 0.10 kg of D.C.P. |
100 Kg of mixture will give 83kg of T.D.N. and 10kg of D.C.P.
The protein is correct for milk production although the T.D.N. is rather high. This could be sorted out by using a protein feed with less energy than cotton seed.
A common practice among dairy farmers is to buy a concentrate from a food firm and mix this with maize which they have available on the farm. These concentrate foods are made to be mixed with maize and the food firms specify the rate of mixing e.g. 3 to 1 means 3 parts of maize to 1 part of concentrate. These concentrate mixtures are an easy and relatively economical way of making up a production ration for milking cows, because when they are mixed with maize and the resulting mixture will contain the correct quantities of T.D.N., D.C.P. and minerals.
To give you some practice at working out a dairy ration calculate the nutrients supplied by the following ration and see if they are correct for milk production. Try to work this out for yourself before looking at the answer.
| T.D.N. | D.C.P. | |
| 18 x 90kg of maize meal | 80 | 6.5 |
| 7 x 90kg of cottonseed | 90 | 17.0 |
| 8 x 50kg of dairy concentrate | 75 | 37.5 |
Answer:
| T.D.N. | D.C.P. | |
| 1620kg of maize will supply | 80/100 x 1620 = 1296kg | 6.5/100 x 16.20 = 10.530 |
| 630kg of cottonseed will supply | 90/100 x 630 = 567kg | 17/100 x 630 = 107.10 |
| 400kg of dairy concentrate will supply | 75/100 x 400 = 300kg | 37.5/100 x 400 = 150.00 |
| 2650kg mixture will supply | 2163kg | 267.63kg |
| 1kg mixture will supply | 2163/2650 = 0.81 | 267.63/2650 = 0.10 |
100kg mixture will supply 81kg of T.D.N. and 10kg of D.C.P.
Try another exercise without looking at the answer first. Using the following ingredients and calculate a ration to be fed to dairy cows giving milk of 4% butterfat:
| T.D.N. | D.C.P. | |
| Maize | 80 | 7 |
| Sunflower seed cake | 75 | 37 |
| Decorticated cottonseed meal | 73 | 33 |
Answer:
The requirement for milk of 4% butterfat is 0.33kg T.D.N. and 0.051kg of D.C.P. per kg of milk produced.
Feeding at 0.5kg per 1kg of milk will need a meal mixture with a D.C.P. of 0.051 x 100 ¸ 0.5 = 10%, and a T.D.N. of 0.33 x 100 ¸ 0.5 = 66% T.D.N.
Looking at the D.C.P. of sunflower seed cake and cottonseed meal, we can see that they are very similar; we will use the average for the 2 (35) for Pearson’s Square
We can substitute cottonseed meal for sunflower seed meal, and in order to work with whole numbers, we will simply double the quantities, i.e. 16 parts maize, 2 parts high protein meal of which 1 part will be sunflower seed meal and 1 part cottonseed meal. Our ration is:
- 16kg Maize Meal
- 1kg Sunflower Seed Meal
- 1kg Cottonseed Meal
Check if this is correct using the following table:
| Calculation | T.D.N. | D.C.P. | |
| 16kg maize will provide | 80/100 x 16 | 12.80 | 7/100 x 16 = 1.12 |
| 1kg sunflower seed will provide | 7/1005 x 1 = | 0.75 | 35/100 x 1 = 0.35 |
| 1kg cottonseed will provide | 73/100 x 1 = | 0.73 | 33/100 x 1 = 0.33 |
| 18kg of mixture will provide | 14.28 | 1.80 | |
| 1kg of mixture will provide | 14.28/18 = 0.79 | 1.80/18 = 0.10 | |
| 100kg of mixture will provide | 79kg | 10kg |
This mixture will provide enough protein and more than enough energy for milk production.
