Following are some key points to aid in prevention of metabolic problems:
- Supplementing with magnesium will reduce the risk of milk fever and grass staggers (grass tetany)
- Supplement with magnesium daily for two to three weeks pre-calving until after spring pasture growth rates have slowed (around December)
- It can be difficult to supply cows with enough magnesium just through the water supply
Combine magnesium through the water supply with magnesium dusted daily onto pasture or silage - Dietary requirements of magnesium will vary due to cow liveweight (dependent on breed) as shown in Table 2 (Refer to Magnesium supplementation (Farmfact 3-1) for dose rates of magnesium from different sources to meet daily requirements)
- After calving, provide 150g/cow/day ground limestone (lime flour) daily during the colostrum period- double this rate if dusting; can also consider calcium-enriched molasses
- Springer cows should not be over-fed. Cows that are at or above BCS targets should be fed at 90% of requirements for 2 to 3 weeks pre-calving, while cows below BCS targets should be fed at 100% of requirements (Table 1).
- Consider using starter drenches on high risk cows at calving - 7+ year olds, or very fat, or with a history of metabolic problems.
Feeding level
Cows that are at or above BCS targets should be fed at 90% of requirements for 2 to 3 weeks pre-calving, while cows that are below BCS targets should be fed at 100% of requirements.
Table 1.
BCS below 5.0 |
|
BCS 5.0 and above |
||||
LWT |
ME required |
DMI required* |
|
LWT |
ME required |
DMI required* |
350 |
85 |
7.7 |
|
350 |
76 |
6.9 |
400 |
94 |
8.5 |
|
400 |
84 |
7.6 |
450 |
102 |
9.3 |
|
450 |
92 |
8.4 |
500 |
111 |
10.1 |
|
500 |
100 |
9.1 |
550 |
119 |
10.8 |
|
550 |
107 |
9.7 |
* ME = 11 MJ/kg DM
Table 2. Dietary magnesium requirements and supplementation recommendations
|
Mg requirement (% of diet) |
Supplementary Mg (g/cow/day) |
||
Jersey |
JxF |
Friesian |
||
Dry |
0.35% |
12 |
16 |
20 |
Lactating |
0.28% |
15 |
17 |
20 |