Table 2.

Demonstrated effects of hops and hops bitter acids or ionophores.

Effect	Hops (or hops bitter acid)	Ionophores
Animal performance
Increased average daily gain	Yes (96), no (93)	Yes (14, 17, 22)a
Increased gain:feed	No (93, 96)	Yes (14, 17, 98)
Increased carcass weight	No (96)	Yes (14, 17, 98)
Rumen metabolism
Increased pH	Yes (83, 93), No (93, 94)	Yes (14, 17, 18, 83, 98)
Decreased A:P	Yes (83, 96, 97), No (93)	Yes (14, 17, 18, 83, 98)
Decreased ${\text{NH}}_4^{+}$	Yes (84, 85, 97)	Yes (14, 17, 18, 98)
Decreased CH4	Yes (93, 97)	Yes (14, 17, 18, 98)
Other benefits
Decreased coccidia	Not reported	Yes (14, 17)

References discussing the effects listed in the first column are given in parentheses, with yes references supporting the increase or decrease following hops or ionophore treatment and no references not supporting the listed increase/decrease.

Gain:feed, amount of weight gained relative to the amount of feed given; A:P, acetate-to-propionate ratio; ${\text{NH}}_4^{+}$, ammonium or ammonia; CH₄, methane.

^aReferences (14, 17, 98) are reviews of ionophore research, rather than discrete studies.