Effects of phytogenic feed additives on growth performance and on ammonia and greenhouse gases emissions in growing-finishing pigs

Abstract

The present study was conducted to evaluate the effects of two commercial phytogenic feed additives (PFAs) on growth performance and emissions of ammonia, methane, nitrous oxide and carbon dioxide compared to an unsupplemented control. The two tested commercial PFAs contained either essential oils or a mixture of essential oils and dried herbs and spices. In addition, both PFAs delivered the same amount of Quillaja saponaria saponins to the final feed, although dosage of the products differed. The PFAs were included in cereal-based grower and finisher diets via premixes. For negative control diet a placebo premix was used. The diets were fed to a total of 81 castrated male growing-finishing pigs (45–114 kg body weight, 27 per treatment) that were kept in nine gas-tight sealed chambers, each with three pens with fully slatted floors (three pigs per pen). The whole experiment lasted 72 days. Pigs were individually weighted and the feed consumption of pigs was recorded per pen at day 0, 24 and 72 of the experiment. From day 24 to day 72 (48 days) emission measurement took place.

The inclusion of the PFAs significantly improved average daily feed intake (P = 0.010) and average daily gain (P = 0.018) of pigs over the whole trial period of 72 days compared to the negative control. Feed conversion ratio was not affected by the treatments (P > 0.05). Pigs that were fed with the PFAs had 3.6% higher final body weight (P = 0.017) compared to the negative control. The inclusion of the PFAs reduced ammonia emissions per animal per day (P = 0.003) as well as per kg body weight gain of pigs (P < 0.001) on average by 21% and 26%, respectively, and tended to reduce carbon dioxide emissions per kg body weight gain (P = 0.092) on average by 9% compared to the negative control. Methane and nitrous gas emissions were not affected by the inclusion of the PFAs (P > 0.05).

In summary, it might be speculated that the observed increased intake and consequently higher growth was mediated via flavoring properties of the PFAs, irrespective of differences in composition. The reduction of ammonia emissions most probably was due to the inclusion of the quillaja saponins in the PFAs. It can be concluded that the tested PFAs have a potential as performance enhancers and are useful tools for the reduction of ammonia emissions from pig barns. Further research is warranted to identify the exact modes of action of PFAs.