To study the effects of an extract of plant flavonoids [Bioflavex (FL)] in cattle fed highconcentrate diets, 2 experiments were designed. In the first experiment, the effects of Bioflavex on the development of rumen acidosis was evaluated in 8 Holstein-Friesian crossbreed heifers (451 kg; SEM 14.3 kg of BW) using a crossover design. Each experimental period lasted 22 d; from d 1 to 20, the animals were fed rye grass, on d 21 the animals were fasted, and on d 22, rumen acidosis was induced by applying 5 kg of wheat without [Control: (CTR) heifers who did not receive Bioflavex] or with flavonoids [heifers who received FL; 300 mg/kg DM] through a rumen cannula. Rumen pH was recorded continuously (from d 19 to d 22). On d 22, average rumen pH was significantly (P < 0.01) higher in the FL animals (6.29; SEM = 0.031) than it was in the CTR heifers (5.98; SEM = 0.029). After the wheat application, the rumen VFA concentration increased (P < 0.01), the proportion of acetic acid decreased (P < 0.01), and lactate concentration (mmol/L) increased, but the increase was not as great (P = 0.09) in the FL as it was in the CTR heifers (0.41 to 1.35 mmol/L; SEM = 0.24). On d 22, Streptococcus bovis and Selenomonas ruminantium titers increased after the wheat application, but Megasphaera elsdenii titers increased (P < 0.05) only in the FL heifers. In the second experiment, the effect of Bioflavex on the performance and rumen fermentation in finishing heifers was evaluated. Forty-eight Fleckvieh heifers (initial BW = 317 kg; SEM = 5.34) were used in a completely randomized design. Heifers were assigned to 1 of 4 blocks based on their BW and, within each block, assigned to 1 of 2 pens (6 heifers/pen). In addition, 16 heifers (2/pen) were rumen cannulated. Individual BW and group consumption of concentrate and straw were recorded weekly until the animals reached the target slaughter weight. Supplementation with FL did not affect ADG, feed consumption, or feed conversion ratio. Rumen pH and molar proportions of propionate were greater (P < 0.01) and acetate proportion was less in the FL (P < 0.01) than they were in the CTR heifers. Flavonoid supplementation might be effective in improving rumen fermentation and reducing the incidence of rumen acidosis. This effect of flavonoids may be partially explained by increasing the numbers of lactateconsuming microorganisms (e.g., M. elsdenii) in the rumen.

Està subjecte a una llicència de Reconeixement-NoComercial-SenseObraDerivada 4.0 de Creative Commons The effect of Bioflavex ® and its pure flavonoid components on in vitro fermentation parameters and methane production in rumen fluid from steers given high concentrate diets

Dietary supplementation with linseed, saponins, and nitrate is a promising methane mitigation strategy in ruminant production. Here, we aimed to assess the effects of these additives on the rumen microbiota in order to understand underlying microbial mechanisms of methane abatement. Two 2-by-2 factorial design studies were conducted simultaneously, which also allowed us to make a broad-based assessment of microbial responses. Eight nonlactating cows were fed diets supplemented with linseed or saponin in order to decrease hydrogen production and nitrate to affect hydrogen consumption; also, combinations of linseed plus nitrate or saponin plus nitrate were used to explore the interaction between dietary treatments. Previous work assessed effects on methane and fermentation patterns. Rumen microbes were studied by sequencing 18S and 16S rRNA genes and ITS1 amplicons. Methanogen activity was monitored by following changes inmcrAtranscript abundance. Nitrate fed alone or in combination in both studies dramatically affected the composition and structure of rumen microbiota, although impacts were more evident in one of the studies. Linseed moderately modified only bacterial community structure. Indicator operational taxonomic unit (OTU) analysis revealed that both linseed and nitrate reduced the relative abundance of hydrogen-producingRuminococcaceae. Linseed increased the proportion of bacteria known to reduce succinate to propionate, whereas nitrate supplementation increased nitrate-reducing bacteria and decreased the metabolic activity of rumen methanogens. Saponins had no effect on the microbiota. Inconsistency found between the two studies with nitrate supplementation could be explained by changes in microbial ecosystem functioning rather than changes in microbial community structure.IMPORTANCEThis study aimed at identifying the microbial mechanisms of enteric methane mitigation when linseed, nitrate, and saponins were fed to nonlactating cows alone or in a combination. Hydrogen is a limiting factor in rumen methanogenesis. We hypothesized that linseed and saponins would affect hydrogen producers and nitrate would affect hydrogen consumption, leading to reduced methane production in the rumen. Contrary to what was predicted, both linseed and nitrate had a deleterious effect on hydrogen producers; linseed also redirected hydrogen consumption toward propionate production, whereas nitrate stimulated the growth of nitrate-reducing and, hence, hydrogen-consuming bacterial taxa. This novel knowledge of microbial mechanisms involved in rumen methanogenesis provides insights for the development and optimization of methane mitigation strategies.

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Està subjecte a una llicència de Reconeixement-NoComercial-SenseObraDerivada 3.0 de Creative Commons

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In this study we investigated the impact of dietary protein and carotene levels on microbial functions and composition during the last month of purebred fattening Duroc pigs. Fecal microbiota was characterized using 16S ribosomal RNA sequencing at two points of live, 165 (T1) and 195 (T2) days. From 70 to 165 days of age, 32 pigs were divided into two groups fed either a standard-protein (SP) or a low-protein (LP) diet. In the last month (165–195 days), all pigs received a LP diet, either carotene-enriched (CE) or not (NC). Significant differences were observed between T1 and T2 at Amplicon Sequences Variants (ASVs), phylum and genus levels. In T1 group, Prevotella, Faecalibacterium and Treponema were the genera most influenced by dietary protein, together with predicted functions related with the degradation of protein. In contrast, the CE diet did not impact the microbiome diversity, although 160 ASVs were differentially abundant between CE and NC groups at T2. Weak stability of enterotype clusters across time-points was observed as consequence of medium-term dietary interventions. Our results suggest that during the last month of fattening, dietary protein have a stronger effect than carotenes on the modulation of the compositional and functional structure of the pig microbiota.

Nutritional and genetic strategies are needed to enhance intramuscular fat (IMF) and MUFA content without altering carcass leanness. Dietary vitamin A restriction has been suggested to specifically promote IMF, whereas a polymorphism of the () gene has shown to specifically increase MUFA. The purpose of this study was to investigate the combined effects of provitamin A (PVA) carotenoid intake and genotype (>) on hepatic retinoid content and on the liver, muscle (LM and gluteus medius [GM]), and subcutaneous fat (SF) content and fatty acid composition. Following a split-plot design, 32 castrated Duroc pigs, half of each of the 2 homozygous genotypes (CC and TT), were subjected from 165 to 195 d of age to 2 finishing diets differing in the PVA carotenoid content (an enriched-carotene diet [C+] and a control diet [C-]). Both diets were identical except for the corn line used in the feed. The C+ was formulated with 20% of a carotenoid-fortified corn (M37W-Ph3) whereas the C- instead used 20% of its near isogenic M37W line, which did not contain PVA carotenoids. No vitamin A was added to the diets. The C- was estimated to provide, at most, 1,300 IU of vitamin A/kg and the C+ to supply an extra amount of at least 800 IU vitamin A/kg. Compared with the pigs fed the C-, pigs fed with C+ had 3-fold more retinoic acid ( < 0.01) and 4-fold more gene expression in the liver ( = 0.06). The diet did not affect performance traits and backfat thickness, but pigs fed the C+ had less fat (4.0 vs. 5.0%; = 0.07) and MUFA (18.3 vs. 22.5%; = 0.01) in the liver, less IMF (5.4 vs. 8.3%; = 0.04) in the GM, and more fat content (90.4 vs. 87.9%; = 0.09) and MUFA (48.0 vs. 46.6%; = 0.04) in SF. The TT genotype at the gene increased MUFA ( < 0.05) in all tissues (21.4 vs. 19.5% in the liver, 55.0 vs. 53.1% in the LM, 53.9 vs. 51.7% in the GM, and 48.0 vs. 46.7% in SF for TT and CC genotypes, respectively). Liver fat and MUFA content nonlinearly declined with liver all- retinoic acid, indicating a saturation point at relatively low all- retinoic acid content. The results obtained provide evidence for a complementary role between dietary PVA and genotype, in the sense that the TT pigs fed with a low-PVA diet are expected to show higher and more monounsaturated IMF without increasing total fat content.