The objective of our study was to determine the effect of two hop varieties, Dana and Aurora, on rumen microbial activity, determined with in vitro gas production. The total potential gas production, gas production till 24 h of incubation and time of maximum fermentation rate were affected by the hop variety, while hop concentration affected also the maximum fermentation rate. The concentrations of volatile fatty acid in the inocula after 24 hours of incubation only partially confirmed above mentioned results. The Dana variety caused greater decrease of acetic and butyric acid than Aurora variety, while the propionic acid even increased with the use of Dana variety.
Hop alpha- and beta-acids are hop secondary metabolites whose application and function, till now, is well known in brewing, particularly of alpha-acids. In spite of their small and insufficient effect on productivity of dairy animals and also on milk quality, on the beginning of this century it was found the antibiotic effect of hop acids, because they decrease the population of gram-positive bacteria and protozoa in digestive track of ruminants. It is well known that higher population of gram-positive bacteria in animal feed and/or on pastures cause lower efficiency of animal feed and even infective diseases of digestive track. In these cases the most often therapy is antibiotic treatment with ionophores class of antibiotics. However, hop acids because of their specific chemical structure, have impact equal to ionophores and hop pellets could be added in hop feed in prevention. Apart from direct effect on decrease population of gram-positive bacteria, the emission of methane from animal waste is also decrease. Using of hops in feeding of ruminants has also a big economical importance, particularly from the aspect of organic dairy production, moreover, nowadays a non-clinical usage of antibiotic stimulators of animal growth in intensive cattle breeding is prohibited and on the other hand, researching of alternative matters (probiotics, prebiotics and immunomodulators) and their application as additives in animal feed has been increased. However, big hop surplus on the world market; hops and hop pellets are more accessible than ever.
Hop growing is one of the main branches in Slovenian agriculture. With ban of antibiotics in animal nutrition in EU, the economics of animal production is reduced and for this reason effective substitutes are intensively researched. Because of the needs for supplying safe food to consumers and saving the sustainable Slovenian hop growing, we did the experiment on growing chickens with the intention to research the antioxidative effect of hops and their influence on animal health, performance and meat quality. Broiler chickens Ross 308 (N=84) were included in the nutritional study. Animals were divided into three groups. The diets were supplemented with linseed oil (7.5 %), which is high in n-3 PUFA. The experimental diets where as follows: 1. Diet - no additives (CONT), 2. Diet - HOPS_0.9: CONT + 0.9 g hops/kg of diet and 3. Diet - HOPS_3.6: CONT + 3.6 g hops/kg of diet. Animal performance and health, feed consumption, oxidative stress and meat quality and oxidative stability of chicken meat were evaluated. Oxidative stress in vivo was studied by measuring the DNA damage of blood cells, measuring malondialdehyde (MDA) in plasma, and analysing the antioxidant capacity of the lipid (ACL) and water (ACW)-soluble compounds. The hop supplementation did not influence chicken performance. The supplement of 3.6 g hop/kg induces MDA formation and decreases DNA fragmentation. ACL was significantly reduced in the group supplemented with 3.6 g hops/kg in comparison to the group CONT. Further studies are needed to confirm the results of the present study.