The U.S. Agriculture Department (USDA) has now formally closed its investigation of the first native U.S. case of mad cow disease, in June this year.
The conclusion reached was that the Texas animal was infected before a federal ban on using cattle remains in cattle feed was imposed in 1997.
This was the first incident involving a U.S.-born cow and only the second U.S. case ever, found in a Holstein dairy cow imported from Canada to Washington state in 2003.
One of the Food and Drug Administration (FDA) roles is to monitor animal feed, and the organization says it now aims to refine the livestock feed ban with an additional rule.
According to Stephen Sundlof, director of Food and Drug Administration's (FDA) Center for Veterinary Medicine, the FDA is considering a broader ban on the use of poultry litter, table scraps and cattle blood in feed as well as placing more restrictions on the use of items thought to carry the highest risk of spreading mad cow disease.
BSE which is always fatal, is believed to be spread among cattle through consumption of feed that contains material from infected cattle.
By eating contaminated meat, people can contract a human version of the disease.
The feed ban is a prohibition against slaughtering "downer" cattle, animals too sick to walk on their own, for human food, and a requirement for meat packers to remove from carcasses the brains, spinal cords, nervous tissue and other parts most likely to contain the malformed proteins blamed for the disease, and is the main safeguard against mad cow disease in the U.S.
Agriculture Secretary Mike Johanns is reportedly pleased that investigation is closed and trading partners can now be notified.
He renewed his frequent calls on Japan to "step up" and resume purchases of beef from young cattle, as it agreed to do last year.
The 12-year-old, cream-colored cow at the heart of the latest scare was selected for testing when it was delivered dead to a pet food plant in Waco last November 15.
Initially it was declared free of mad cow disease but a new round of tests in June, ordered by the USDA inspector general, found the cow had bovine spongiform encephalopathy (BSE), or mad cow disease.
The USDA went on to confirm that their investigation found that no feed or feed supplements used on the farm since 1997, were formulated to contain prohibited mammalian protein.
The FDA then concluded that the animal was most likely infected prior to the 1997 BSE/ruminant feed rule.
As many as 67 head of cattle, originating from the same farm, were tested for mad cow disease, but all tested negative, and this was confirmed by USDA chief veterinarian John Clifford.
The FDA said its investigation showed U.S. feed mills and packing plants complied with the 1997 ban on using cattle parts in cattle feed.