18 Comparison between drying methods and storage time on the functional value of a trubs, hops, and yeast mixture, on growth performance and intestinal health of nursery pigs

A trubs, hops, and yeast mixture (THYM) generated as a co-product of craft brewing contains high levels of hop acids and yeast cells, bioactive compounds that could positively influence health and growth in pigs. These co-products have a high moisture content and must be dried to facilitate transport and mixing into diets. Drying methods utilizing heat can cause the loss of functional volatile compounds, like hop acids, but the cost of drying solutions using lower heat, such as freeze-drying, can be up to 10-fold the cost of drum-drying. Similarly, it was found that the storage of 3-year-old drum-dried THYM decreased the amount of alpha and beta acids compared with the fresh drum-dried and freeze-dried THYM by approximately 19% and 65%, respectively. Therefore, the purpose of this study was to investigate the efficacy of THYM (Highland Brewing, Asheville, NC, USA) dried using different methods and storage times on intestinal health and growth performance of nursery pigs. Thirty-two pigs (6.8 ± 0.4 kg body weight) weaned at 3 weeks-of-age were allotted into 4 dietary treatments, using a randomized complete block design, with sex and initial body weight as blocks. The dietary treatments were: 1) basal diet (CON); 2) fresh drum-dried THYM, at 0.7% of the diet (0.7DF); 3) fresh freeze-dried THYM, at 0.7% of the diet (0.7FF); and 4) 3-year-old drum-dried THYM, at 1.4% of the diet (1.4DS), to consider the loss of hop acids during storage. The THYM replaced a mixture of 40% corn and 60% soybean meal in the basal diets. Pigs were fed for 28 d in 3 phases (9, 11, and 8 d, respectively). On d 28, all pigs were euthanized for sampling of jejunal tissue and jejunal mucosa. Data were analyzed using SAS 9.4. The inclusion of THYM decreased (P < 0.05) Helicobacter in the jejunal mucosa, when compared with the CON, whereas there were no changes to intestinal morphology and weight gain with the inclusion of THYM. The 1.4DS tended to decrease the expression of Toll-like receptor 2 (P = 0.073) and Cluster of differentiation 14 (P = 0.057), when compared with 0.7DF. This suggests THYM may positively influence the mucosa-associated microbiota, whereas increased storage time could decrease the stimulation of pathogen recognition pathways by THYM, possibly due to storage conditions decreasing the functionality of the bioactive compounds over time. In conclusion, the inclusion of THYM could reduce potentially harmful bacterial populations in the jejunal mucosa, with no negative effects on intestinal morphology or growth performance, however, prolonged storage could decrease immunomodulatory properties of THYM related to pathogen sensing, when fed to nursery pigs.