High Desert Hemp Varieties Under Varied Nitrogen Fermentation Techniques Effects on Its Utilization as Livestock Feed Through in Vitro Fermentation

Abstract Nitrogen fertilizing of hemp varietals in high the high desert may assist in ensuring that production levels match the demand for growing hemp varietals. However, altering fertilizer levels may differently affect plant biomass and cannabinoid concentrations of plant tissues which changes the potential by-product utilizable for livestock feed. This study aimed to determine the influence of hemp fractions [flower (FL) vs stem and leaves (SL)] under three nitrogen fertilization regimens (0, 100, and 200 kg· ha-1) on in vitro rumen fermentation. Incubations runs consisted of triplicates of 500-mL bottles containing approximately 0.5 g of either ground SL or FL of hemp at the three nitrogen fertilization regimens. Rumen fluid was collected from two ruminally cannulated Angus steers, filtered through four layers of cheesecloth, and diluted to 4:1 with a standard buffer solution. A total incubation volume of 75 mL of the buffer: rumen fluid mix was added to each flask. Flasks were then placed in a rotating incubator (55 rpm) at 39°C, connected to an Ankom RF gas production system (Ankom Technology, Macedon, NY), and removed after 24, 48, and 96h. Total gas production (TGP), metabolizable energy (ME), ammonia nitrogen concentration (N-NH3), and total volatile fatty acids (VFA) were determined. Data were analyzed as a completely randomized design using lmer function in lme4 package in R with treatment and time as a fixed effect and replicates as a random effect. Statistical significance was established at P < 0.05 (Table 1). No differences were observed for N-NH3 (P > 0.05). Overall, SL samples had greater total VFA than FL, with T0SL having the greatest concentration among all treatments (P < 0.01). In congruence, acetate, isobutyrate, isovalerate, and the ratio between acetate and propionate concentrations were also greater for T0SL (P < 0.01). Concentrations of butyrate were greater for T200SL (P < 0.01), while T100SL had the greatest concentration of butyrate among all the treatments (P < 0.01). Overall, SL fractions of hemp seem to be more suitable as a ruminant feed source. The greater fat content of the FL compared with SL may detrimentally affect microbial populations and should further be explored. From our results, N supplementation significantly alters fermentation patterns during in vitro, which further warrants the evaluation of these feeds on in vivo experiments.