Trace Minerals in Poultry Nutrition: Zinc, Copper and Manganese
Trace minerals are needed in tiny amounts but their impact on poultry performance is massive. I’ve seen flocks with adequate protein and energy underperform simply because trace mineral levels were wrong. The difference between marginal and optimal trace mineral nutrition can be 3-5 points in feed conversion.
Zinc: The Most Versatile Trace Mineral
Zinc is involved in more enzyme systems than any other trace mineral. It’s essential for over 300 enzymes that regulate everything from cell division to immune function.
The broiler requirement for zinc is around 40-60 ppm from the diet. But natural ingredients provide only 20-30 ppm, so supplementation is needed.
I use zinc at 80-100 ppm in starter feeds, dropping to 60-80 ppm in finishers. The extra zinc in starters supports the rapidly developing immune system. A study from the University of Arkansas showed that broilers receiving 100 ppm zinc had 25% higher antibody titers after Newcastle vaccination compared to those receiving 40 ppm (P<0.05).
The source matters. Zinc oxide (72% zinc) is cheap but only about 50% bioavailable. Zinc sulfate (36% zinc) is more available but can be reactive in premixes. Zinc methionine and zinc glycinate (organic chelates) are the most available but cost 3-5 times more than zinc oxide.
In my formulations, I use a 50:50 blend of zinc oxide and zinc sulfate for standard production and replace 30% with zinc methionate for breeders and antibiotic-free production.
Copper: Gut Health and Growth
Copper is unique among trace minerals because at high levels (125-250 ppm), it acts as a growth promoter. The mechanism is antibacterial. High copper levels reduce bacterial populations in the gut similar to what antibiotic growth promoters do.
The standard requirement for copper is only 8-10 ppm. But many nutritionists use copper at 125-175 ppm from copper sulfate for its growth-promoting effects. This practice has been around since the 1960s and still works.
The catch with high copper is environmental. Most of the copper passes through the bird into the litter, where it accumulates. In areas with intensive poultry production, soil copper levels near poultry houses can become elevated over time.
New alternatives are emerging. Copper tri-basic chloride (Cu2(OH)3Cl) has higher bioavailability than copper sulfate. I can use 100 ppm of the tri-basic chloride and get the same growth promotion as 150 ppm from copper sulfate, with 30% less copper excreted.
Manganese: Bone and Eggshell Quality
Manganese is essential for proteoglycan and cartilage formation. It’s also a cofactor for the enzyme that synthesizes the eggshell membrane.
Broiler requirements for manganese are 60-80 ppm. Layer requirements are similar, but the impact on eggshell quality makes it critical for layer diets. Manganese deficiency in layers produces eggs with thin shells and poor shell strength even when calcium and phosphorus levels are adequate.
One study found that increasing dietary manganese from 60 ppm to 100 ppm improved eggshell breaking strength by 8.5% in 60-week-old laying hens.
Manganese sulfate is the standard source. Manganese methionate has higher bioavailability but is rarely cost-justified for chickens. For turkeys, which have higher manganese requirements (80-100 ppm), I sometimes use organic sources.
Iron: Important but Easily Overdone
Iron is essential for hemoglobin formation and oxygen transport. The requirement is 40-80 ppm. Most feeds meet this without supplementation because iron is abundant in feed ingredients.
The bigger problem with iron is excess. High iron levels (above 500 ppm) can cause toxicity, particularly in young birds. Iron also catalyzes oxidation of vitamins in the feed. I’ve seen premixes where iron oxide caused 50% vitamin A destruction within 30 days of storage.
Iodine and Selenium
Iodine is needed at 0.5-1.0 ppm for thyroid function and metabolism. Potassium iodide or calcium iodate are the standard sources. I prefer calcium iodate because it’s more stable in premixes.
Selenium was covered in a previous article, but I’ll mention here that I use 0.2-0.3 ppm total selenium with a blend of sodium selenite and selenium yeast.
Organic vs Inorganic: The Real Story
There’s a lot of marketing pressure toward organic (chelated) trace minerals. In my experience, the benefit is real but situational:
- Breeders and layers: Organic trace minerals improve hatchability, egg quality, and chick quality. The extra cost is usually justified.
- Broiler starters: Moderate benefit. I use 30-40% organic minerals.
- Broiler finishers: Minimal benefit. Stick with inorganic sources.
A comprehensive trial comparing 100% inorganic vs 50% organic trace minerals showed:
| Parameter | 100% Inorganic | 50% Organic |
|---|---|---|
| Body weight (g) | 2,580 | 2,610 |
| FCR | 1.78 | 1.76 |
| Mortality (%) | 3.2 | 2.8 |
| Bone ash (%) | 42.1 | 43.5 |
The improvements are real but modest. For my formulations, the standard is 100% inorganic for broiler finishers, 30-40% organic for starters, and 50% organic for breeders and layers.