Magnesium calcium and energy

Magnesium supplementation is an important tool to help prevent metabolic issues.

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 supplyCombine 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.

Table 2. Dietary magnesium requirements and supplementation recommendations