A plurality of US patents, such as U.S. Pat. No. 8,197,863B2, U.S. Pat. No. 8,012,516B2, US20080213342A1, US20060269588, US20040219240, U.S. Pat. No. 7,090,873, US20060134248, US20110311663, U.S. Pat. No. 7,553,504, US20130018106 and U.S. Pat. No. 6,251,461, and as plurality of European patents, such as EP2606742A1, EP1542543B1, EP2429311A2 and EP1722635B1, have disclosed the application of hops acids and hydrogenated β-acids as substitutes for antibiotic growth promoters used in feed.
However, recited in the above-mentioned patents is the application of extracts from hops or hops acids (e.g. a mixture of α-acids and β-acids) as feed additives those already included in the Chinese Feed Additive Catalogue but only serve as condiment for feed. Secondly, the grounds of the patents are mainly results of trial in vitro rather than feeding trial. What's more, there is no data so far, to demonstrate safety and stability of these natural products, or the salts and ester thereof, as animal feed additives.
Hexahydro-β-acids are also mentioned in the above-mentioned patents, but application of the esters, salts or ester salts thereof as animal feed additives has not been reported so far.