Macadamia integrifolia husk has great potential for use as a feedstuff in ruminants. However, little information regarding its effects on ruminal fermentation traits is available at present. Hence, this in vitro study aims to investigate the effects of Macadamia integrifolia husk as a substrate, supplemented with enzymes at different levels (0 g/kg cellulases + pectinases, CON; 0.5 cellulases + 0.5 g/kg pectinases, TRE1; 1.0 g/kg cellulases + 0.5 g/kg pectinases, TRE2; 1.5 cellulases + 0.5 g/kg pectinases, TRE3), on gas production, fermentation traits, and bacterial communities in goats. The results demonstrate that gas production was increased in TRE1 and TRE3 groups compared to the CON group at 6, 9, 12, 24, and 48 h (p < 0.05); DMD was the highest in the TRE3 group and the lowest in the CON group at 6, 12, 24, and 48 h (p < 0.05); and NDFD was the highest in the TRE1 group and the lowest in the CON group at 6 h, then the highest in the TRE3 group and the lowest in the CON group at 12, 24, and 48 h (p < 0.05). The concentrations of MCP, TVFAs, acetate, and propionate were the highest in the TRE3 group and the lowest in the CON group (p< 0.05). The abundance of Bacillota was the highest in the TRE1 group and the lowest in the TRE2 group (p < 0.05), whereas that of Synergistota and Actinomycetota was the lowest in the CON group and the highest in the TRE2 group (p < 0.05). Acidobacteriota was the most abundant in the TRE3 group and the least abundant in the TRE1 group (p < 0.05). The most abundant genus was norank_p_Bacteroidota, comprising approximately 29.3%, 30.6%, 30.4%, and 31.7% of the total bacteria in the CON, TRE1, TRE2, and TRE3 groups, respectively; this was followed by Succiniclasticum, comprising approximately 6.3%, 5.8%, 6.1%, and 7.0% of the total bacteria in the CON, TRE1, TRE2, and TRE3 groups, respectively. This study provides new insights regarding the use of Macadamia integrifolia husk as a feedstuff in goats; in particular, supplementation with cellulases and pectinases could effectively improve its utilization. The results suggest that the optimal supplementary levels of cellulases and pectinases are 1.5 g/kg and 0.5 g/kg, respectively.

This study investigated the effects of Bacillus subtilis (B. subtilis) supplementation on microbiota and metabolites in the feces of Leizhou goats. Eight Leizhou goats were used in a replicated 4 × 4 Latin square design according to their gender (nanny goats and billy goats) with a 4 × 2 factorial arrangement of treatments that included four B. subtilis additive doses (control [0 g/d; NC, BC], low [2.5 g/d, NL, BL], medium [5 g/d, NM, BM], and high [7.5 g/d, NH, BH]) and 28 d periods (n = 4 per group), each consisting of 27 d adaption and 1 d sample collection. After collecting 32 fecal samples, 16S rRNA gene sequencing and LC-MS were performed to analyze microbial composition and metabolites, respectively. At the genus level, the relative abundance of Rikenellaceae_RC9_gut_group was significantly higher (p < 0.05) in the NM group than in the NC group. The relative abundance of Treponema sp. was significantly lower (p < 0.05) in the NM group than in the NC group. In billy goats, the relative abundances of UCG-005 and Rikenellaceae_RC9_gut_group were significantly higher (p < 0.05) in the BH group than in the BC group. The relative abundance of Treponema sp. was significantly lower (p < 0.05) in the BL, BM, and BH groups than in the BC group. Furthermore, metabolomic analysis revealed that B. subtilis significantly altered the concentrations of glucose metabolism modulators (1-deoxynojirimycin, 1-DNJ) and certain bioactive peptides. Many amino acid metabolic pathways were also enriched. Correlation analysis demonstrated close connections between differential metabolites and the top 10 bacterial genera in fecal samples. These results provide new insights into the impact of B. subtilis on the microbial community and metabolic profile of the feces of Leizhou goats. In this experiment, the appropriate doses of B. subtilis for nanny goats and billy goats were 5 g/d and 7.5 g/d, respectively, but the optimal doses still need to be verified based on performance-based feeding tests in the next study.

This study was conducted to measure Macadamia integrifolia husk (MIH) as a feed ingredient for goats using an in vitro rumen fermentation system. Four isonitrogenous and isoenergetic substrates were prepared by using MIH to replace 0, 5%, 10%, or 15% of corn as a dry matter basis, namely MIH0, MIH5, MIH10, and MIH15 groups, respectively. Gas production decreased linearly as corn was replaced by increasing levels of MIH. The DMD decreased linearly at the 24 h and 48 h incubation times as corn was replaced by increasing levels of MIH (p < 0.01). The NDFD decreased linearly at the 6 h, 12 h, 24 h, and 48 h incubation times as corn was replaced by increasing levels of MIH. At 48 h, pH differed extremely significantly (p < 0.001) and followed a quadratic trend (p < 0.05). The MIH0 group had the highest NH₃–N, butyric, and isovaleric acids concentration (p < 0.05); the MIH5 group had the highest MCP, acetic acid, and propionic acid concentration (p < 0.05). Bacteroidota and Pseudomonadota were the dominant phyla in the fermentation fluid at the 48 h incubation timepoint among the four groups. The relative abundance of Kiritimatiellota and Synergistota was highest in the MIH15 group. The relative abundance of Pseudomonadota was highest in the MIH5 group. At the genus level, norank_p_Bacteroidota and Ruminobacter were the dominant genera, and the bacterial community structure differed significantly among the four treatments (p < 0.05). In conclusion, we suggest that the MIH replacing 5% of corn did not affect fermentation, VFA profile, or microbial protein synthesis and it could alter the bacterial communities. Moreover, it is necessary to conduct an in vivo study to investigate the growth performance of goats in a further study.

Macadamia integrifolia husk (MIH) is a major byproduct of Macadamia integrifolia processing; however, there is limited information available on its rumen fermentation characteristics and associated bacterial communities when used as a feed for ruminants. This study evaluated the effects of different Bacillus subtilis (BS; ≥10¹³ CFU/g) inclusion levels on MIH using an in vitro technique. A total of six healthy goats (female, 7-month-old) with an average body weight of 15.20 ± 0.20 kg were selected as rumen fluid donors, and the rumen fluid was collected before morning feeding. Four BS inclusion levels were studied: a control group with 0 g/kg (CON), and three treatment groups supplemented with 1.5 g/kg (low dose, BSL), 3.0 g/kg (medium dose, BSM), and 4.5 g/kg (high dose, BSH) of BS. MIH supplemented with BS improved the gas production at all the observed incubation times (p < 0.05). The in vitro dry matter degradability was increased by 3.5%, 2.0%, and 3.1% in the BSL, BSM, and BSH groups, respectively, compared to the CON group at a 48 h incubation time (p = 0.049). The in vitro neutral detergent fiber degradability was increased by 6.0% and 7.8% in the BSL and BSM groups, respectively, compared to the CON group at a 48 h incubation time (p = 0.027). The in vitro acid detergent fiber degradability was increased by 11.7%, 16.8%, and 3.2% in the BSL, BSM, and BSH groups, respectively, compared with the CON group at the 48 h incubation time (p = 0.014). The concentrations of ammonia-N, microbial protein, total VFAs, acetate, propionate, butyrate, iso-butyrate, valerate, and iso-valerate were quadratically changed with increasing BS supplementation levels (p < 0.05). The relative abundances of Bacteroidota and Pseudomonadota were highest in the BSL group and lowest in the BSM group (p < 0.05), whereas Bacillota and Kiritimatiellota were highest in the BSH group and lowest in the BSL group (p < 0.05). Synergistota was highest in the BSM group and lowest in the BSH group (p < 0.05). The relative abundances of norank_p_Bacteroidota and norank_o_Bacteroidoles were highest in the BSL group, whereas they were lowest in the BSM group (p < 0.05). The relative abundances Hoyesella and Succinivibrio were highest in the BSL group, whereas they were lowest in the BSH group (p < 0.05). The relative abundances of Prevotella, Succiniclasticum, and Selenomonas were highest in the BSM group, whereas they were lowest in the BSL group (p < 0.05). These in vitro results indicate that supplementation with Bacillus subtilis could improve the utilization of MIH in goats, which is possibly associated with the altered rumen bacteria communities. The supplementation of 1.5 to 3.0 g/kg Bacillus subtilis (≥10¹³ CFU/g) on Macadamia integrifolia husk could improve its utilization as a feasible alternative feed for ruminants using an in vitro technique.