Agriculture

• Sources: Forages are generally good sources; grains are poor, annual silages are low.
• Deficiency risks: Abnormal bone growth, reduced milk production, occasional milk fever, and “down cows,” particularly when fed greenfeed-only diets.
• Interactions: Low vitamin D or high dietary phosphorus may mimic calcium deficiency.
• Ca:P ratio: Should be 1.5:1 to 7:1. Ratios below 1.5:1 tolerated only for short periods (<30 days).

Feed Type	Calcium (%)	Phosphorus (%)	Magnesium (%)	Potassium (%)	Sulphur (%)
Alfalfa Hay	Avg: 1.57 Range: 0.63–2.86	Avg: 0.26 Range: 0.14–0.35	0.36	1.85	0.23
Grass–Legume Hay	Avg: 1.48 Range: 0.83–2.28	Avg: 0.20 Range: 0.13–0.30	0.30	1.97	0.16
Grass Hay	Avg: 0.75 Range: 0.36–1.43	Avg: 0.15 Range: 0.09–0.24	0.24	1.71	0.18
Greenfeed	Avg: 0.48 Range: 0.24–0.74	Avg: 0.16 Range: 0.10–0.26	0.24	1.64	0.18
Barley Grain	Avg: 0.06 Range: 0.04–0.06	Avg: 0.32 Range: 0.30–0.34	0.14	0.50	0.13
Native Hay	Avg: 0.74 Range: 0.55–1.02	Avg: 0.08 Range: 0.08–0.16	0.17	1.15	0.10

• Sources: Forages often marginal; grains are good sources.
• Deficiency symptoms: Poor reproductive performance, irregular heats, reduced fertility and conception rates, low intake, pica, and possible bone issues.
• Importance: Adequate vitamin D required. Excess calcium increases phosphorus needs.
• Impact on reproduction: Supplementation significantly improves conception rates and calving intervals.

• Adequacy: Most Manitoba feeds contain sufficient magnesium.
• Interactions: High calcium, phosphorus, or potassium reduce availability.
• Deficiency: Grass tetany—characterized by nervousness, poor coordination, muscle twitching, and potential death. Most common in early spring grazing on lush green pastures or in high-potassium preserved forages.

• Sources: Forages typically adequate; grains low.
• Deficiency: Reduced intake, poor weight gain, rough hair coat.
• Supplements: Mainly required in high‑grain or straw-based rations.

• Adequacy: Most feeds meet requirements for growing or pregnant cattle; heavy-milking cows may be marginal.
• Excess risk: High-sulphate water can reduce copper and selenium absorption, potentially requiring additional supplementation. Chelated minerals may help in high-sulphate/high-molybdenum regions.

• Requirement: Always required; natural feeds do not meet needs.
• High-salt exceptions: Some manured silages and marsh hay may contain elevated levels.
• Deficiency: Reduced appetite, poor condition, decreased milk production.

• Base selection on feed analysis and the mineral deficiencies identified.
• Consider both macro- and trace-mineral needs.
• Compare supplements using cost per pound of phosphorus as it is generally the highest cost in a mineral mix, not cost per ton.
• Example economic return: Improvements in reproduction can justify mineral costs far above typical market prices.

• 0:1 (high phosphorus): For legume-based diets.
• 1:1: Common choice for most grass/legume, cereal, and silage rations.
• 2:1 or 3:1: For high-grain diets.

• Free-choice is common but less precise than force-feeding or top‑dressing.
• Mix salt with mineral and offer as the only salt source to ensure intake. Generally recommended to mix 50% salt and 50% mineral. 
• Monitor and measure consumption regularly to ensure animals meet requirements.

• Dry cows: Lower calcium and phosphorus needs.
• Lactating cows: Higher requirements, especially high-producing animals.
• Growing calves: Highest calcium and phosphorus needs relative to body weight.

Class of Animal	Calcium (%)	Phosphorus (%)	Magnesium (%)	Potassium (%)	Sulphur (%)
Dry Pregnant Cows	0.15	0.11	0.16	0.80	0.16
Lactating Cows – Average Milking Ability	0.33	0.21	0.20	0.80	0.20
Lactating Cows – Superior Milking Ability	0.38	0.24	0.20	0.80	0.20
Growing Calves – 400 lb	0.57	0.30	0.16	0.65	0.16
Growing Calves – 500 lb	0.57	0.30	0.16	0.65	0.16
Growing Calves – 600 lb	0.57	0.30	0.16	0.65	0.16