Producers who feed mineral supplements to their cattle or sheep should pay close attention to how much mineral different animals within the herd are consuming.

Research suggests there's a great deal of variation in individual animal consumption of supplements, says Jan Bowman, a professor in the Montana State University-Bozeman Animal and Range Sciences Department.

"If some animals are getting more than the target amount of supplement, and some animals are getting less than that, it's costing producers money," says Bowman.

Bowman and MSU colleague Bok Sowell analyzed research studies on animal supplement intake, and found that trough size, animal dominance and other factors can influence how much supplement each animal gets.

The cost of mineral supplementation ranges between $2 and $40 per cow per year, according to research. Over-consumption of supplement by certain animals wastes money and has the potential to be harmful to the animals. Animals not getting enough can reproduce or grow at a reduced rate, have decreased feed efficiency and depressed immune systems.

Producers select the amount and type of supplement depending on mineral deficiencies in the forage and other site-specific factors. Producers usually determine a target level of intake per cow or sheep.

Some producers hand-feed certain animals to make sure they are getting a desired amount. But often producers will put out a bulk amount which is intended for the whole herd or flock. The producers usually assume that each animal is getting an equal portion, but often that's not the case, says Bowman.

When animals have free access to supplement, such as in blocks or liquid form, some animals over-consume, while some don't get any.

Trough space can influence competitiveness by the animals. "There seems to be an optimum level of competition," she says. "Too little trough space can mean there are more animals -- generally the less dominant ones -- that don't get any supplement. However, when there's excess trough space, dominant animals chase others away from the trough, and they spend more time fighting than eating.

Research shows that increasing the overall amount of supplement can reduce the effect of trough space. However, when the overall supplement allowance was reduced, trough space had a lot to do with the variation in individual animal supplement intake.

Certain breeds show different dominance traits. Angus cattle are usually more dominant than herefords, and merino sheep are usually less dominant than other sheep breeds.

The research also found that the percentage of non-feeders of supplement increased if lots of forage was available and if the animals were not used to consuming the particular supplement.

Bowman advises producers to observe the animals during supplement feeding to determine whether animal competition is affecting supplement intake. If there are certain animals that need more supplement, such as heifers, producers may want to put them in a separate feeding area.