FARGO - Two North Dakota ranchers say a Colorado company sold and mixed a liquid feed supplement that poisoned their cattle and led to the deaths of two cows and two calves.

Lonnie and Todd McPeak, of Sterling, have filed a civil lawsuit in federal court against Cattleman's Choice Loomix, LLC, accusing the business of negligence. The Johnstown, Colo., company denies the allegations and says the suit should be thrown out.

The McPeaks said they started feeding the Loomix Ore-Bac supplement to their cows and calves in April. The cattle became ill and four animals died from the supplement, the ranchers' complaint said.

The McPeaks claim one of the dealers for the company improperly mixed the feed and caused the release of dangerously high levels of sulfur and nitrogen.

Cattleman's Choice said any damage to the cattle was caused by "misuse or abuse" of the product by the ranchers and was not the company's fault.

"Any product for which defendant (Cattleman's Choice) was responsible at the time of the injuries alleged by plaintiffs (ranchers) was not defective or unreasonably dangerous in any way," the company said in its response.

The lawsuit said the reaction to the mixture stunted the growth of about 350 calves, causing an auction house to advise people against buying the cattle.

"Their appearance is poor and they are not marketable as healthy good quality cattle," the complaint said.

The lawsuit seeks unspecified damages for economic losses and "loss of good reputation."