As temperatures turn colder our calves will need additional energy. This energy supports normal body functions as well as maintaining body temperature. Any energy that is surplus to these basic requirements is available for growth. As the live weight of the calf increases so does its daily maintenance energy requirement.
Milk is the most efficient way to supply additional energy. More than 90% of the gross energy of milk ends up as Metabolisable Energy (ME). Compared with only 50-60% of hay or concentrates. It is also easier to measure and control. Any additional milk should be provided as whole milk or mixed milk replacer rather than using additional powder as this would increase the osmolality of the milk.
The table below outlines the additional MJ of energy required at low temperatures in calves of different ages when aiming to achieve 0.8kg/day of growth.
|
|
0 – 3 weeks |
3 – 6 weeks |
6 – 9 weeks |
9 – 12 weeks |
|
12° |
0.6 |
0 |
0 |
0 |
|
10° |
1 |
0 |
0 |
0 |
|
8° |
1.4 |
0.5 |
0.6 |
0.7 |
|
6° |
1.9 |
1 |
1.2 |
1.4 |
|
4° |
2.3 |
1.5 |
1.8 |
2.1 |
|
2° |
2.7 |
2.1 |
2.5 |
2.8 |
|
0° |
3.1 |
2.6 |
3.1 |
3.5 |
|
-2° |
3.5 |
3.1 |
3.7 |
4.2 |
|
-4° |
3.9 |
3.6 |
4.3 |
4.9 |
In summary, an additional 0.5l of mixed milk replacer (23% protein 20% oil) provides 1.5MJ therefore a calf under 3 weeks of age will need an additional 0.5l when the temperature falls to 8°. If the temperature reaches 0° a whole extra litre a day should be given. Older animals will require additional feed at 4°. Remember older calves have some ability to self-regulate by increasing their starter intake but their rumens are still developing and therefore feed conversion efficiency is limited.
