A lawsuit brought by the Humane Society of the US (HSUS) against the Agriculture Department has argued that the USDA had misinterpreted the 50-year-old Act, reports Cattle Network.

"The court finds the legislative history strongly demonstrates unambiguous congressional intent that livestock, as used in the HMSA, does not include poultry," US District Court Judge Marilyn Hall Patel reportedly wrote in her opinion.

Judge Patel granted summary judgment in USDA's favour and dismissed the lawsuit.

HSUS's argument was based on a 1958 dictionary definition of livestock that said that the word encompassed "useful" animals on a farm, while USDA said that the term has always internally meant to exclude poultry.

"The plain language of these bills indicates that Congress intended to exclude poultry from the definition of livestock when it enacted H.R. 8308, the bill that eventually became the HMSA," Patel wrote.