Stable Carbon Isotope Composition of c 9, t 11-Conjugated Linoleic Acid in Cow's Milk as Related to Dietary Fatty Acids

This study explores the potential use of stable carbon isotope ratios (δ13C) of single fatty acids (FA) as tracers for the transformation of FA from diet to milk, with focus on the metabolic origin of c9,t11-18:2. For this purpose, dairy cows were fed diets based exclusively on C3 and C4 plants. The FA in milk and feed were fractionated by silver-ion thin-layer chromatography and analyzed for their δ13C values. Mean δ13C values of FA from C3 milk were lower compared to those from C4 milk (−30.1‰ vs. −24.9‰, respectively). In both groups the most negative δ13C values of all FA analyzed were measured for c9,t11-18:2 (C3 milk=−37.0±2.7‰; C4 milk −31.4±1.4‰). Compared to the dietary precursors 18:2n-6 and 18:3n-3, no significant 13C-depletion was measured in t11-18:1. This suggests that the δ13C-change in c9,t11-18:2 did not originate from the microbial biohydrogenation in the rumen, but most probably from endogenous desaturation of t11-18:1. It appears that the natural δ13C differences in some dietary FA are at least partly preserved in milk FA. Therefore, carbon isotope analyses of individual FA could be useful for studying metabolic transformation processes in ruminant

Scrophularia striata Extract Supports Rumen Fermentation and Improves Microbial Diversity in vitro Compared to Monensin

In the search for natural alternatives to antibiotic feed additives, we compared the efficacy of two doses of Scrophularia striata extract [S. striata-Low at 40 and S. striata-High at 80 mg g-1 dry matter (DM)] with monensin (monensin) and a negative control in the modulation of rumen fermentation, methane production and microbial abundance in vitro. Microbes were investigated using qPCR and 16S rRNA targeted sequencing. Data showed that the addition of S. striata increased production of total short chain fatty acids (SCFA) in comparison to both monensin and control (P = 0.04). The addition of S. striata increased acetate production, and increased propionate at the higher dosage (P < 0.001). Supplementation of S. striata lowered methane production (P < 0.001) compared to control but with no effect compared to monensin. Ammonia concentration decreased by 52% (P < 0.001) with S. striata-High supplementation (4.14 mmol L-1) compared to control, which was greater than that of monensin (36%). The diversity of rumen bacteria was reduced (P < 0.001) for monensin and S. striata for both the number of observed OTUs and the Chao1 index. Quantitative analysis of Protozoa showed a decrease in the monensin treatment (P = 0.05) compared to control. Archaea copy numbers decreased equally in both S. striata-High and monensin treatments compared to the control group. Supplementation with S. striata increased relative abundances of Fibrobacteres (P < 0.001) and Planctomycetes (P = 0.001) in comparison to both the control and monensin treatments. Significant negative correlations were observed between the abundances of Bacteroides, Fusobacterium, and Succinivibrio genera and methane (r > -0.71; P ≤ 0.001). The abundance of Fibrobacter genera and total SCFA (r = 0.86), acetate (r = 0.75), and valerate (r = -0.51; P < 0.001) correlated positively. These results suggest that S. striata supplementation at 80 mg g-1 DM inclusion, similar to monensin, supports rumen fermentation, lowers methane and ammonia production. However, S. striata supported rumen fermentation toward higher total SCFA and propionate production, while unlike monensin still supported a diverse rumen microbiome and an increase in cellulolytic bacteria such as Fibrobacter

Efficiency of monolaurin in mitigating ruminal methanogenesis and modifying C-isotope fractionation when incubating diets composed of either C3 or C4 plants in a rumen simulation technique (Rusitec) system

Mitigation of methanogenesis in ruminants has been an important goal for several decades. Free lauric acid, known to suppress ruminal methanogenesis, has a low palatability; therefore, in the present study the aim was to evaluate the mitigation efficacy of its esterified form (monolaurin). Further, 13C-isotope abundance (δ13C) and 13C-12C fractionation during methanogenesis and fermentation were determined to evaluate possible microbial C-isotope preferences. Using the rumen simulation technique, four basal diets, characterised either by the C3 plants grass (hay) and wheat (straw and grain), or the C4 plant (13C excess compared with C3 plants) maize (straw and grain), and a mixture of the latter two, were incubated with and without monolaurin (50g/kg dietary DM). Added to hay, monolaurin did not significantly affect methanogenesis. When added to the other diets (P<0·05 for the wheat-based diet) methane formation was lowered. Monolaurin decreased fibre disappearance (least effect with the hay diet), acetate:propionate ratio, and protozoal counts. Feed residues and SCFA showed the same δ13C as the diets. Methane was depleted in 13C while CO2 was enriched in 13C compared with the diets. Monolaurin addition resulted in 13C depletion of CO2 and enrichment in CH4 (the latter only in the hay diet). In conclusion, monolaurin proved to effectively decrease methanogenesis in the straw-grain diets although this effect might partly be explained by the concomitantly reduced fibre disappearance. The influence on 13C-isotope abundance and fractionation supports the hypothesis that ruminal microbes seem to differentiate to some extent between C-isotopes during methanogenesis and fermentatio

Metabolic Profile and Inflammatory Responses in Dairy Cows with Left Displaced Abomasum Kept under Small-Scaled Farm Conditions

Left displaced abomasum (LDA) is a severe metabolic disease of cattle with a strong negative impact on production efficiency of dairy farms. Metabolic and inflammatory alterations associated with this disease have been reported in earlier studies, conducted mostly in large dairy farms. This research aimed to: (1) evaluate metabolic and inflammatory responses in dairy cows affected by LDA in small-scaled dairy farms; and (2) establish an Animals 2015, 5 1022 association between lactation number and milk production with the outcome of metabolic variables. The cows with LDA had lower serum calcium (Ca), but greater concentrations of non-esterified fatty acids (NEFA) and beta-hydroxy-butyrate (BHBA), in particular when lactation number was &gt;2. Cows with LDA showed elevated levels of aspartate aminotransferase, glutamate dehydrogenase, and serum amyloid A (SAA), regardless of lactation number. In addition, this study revealed strong associations between milk yield and the alteration of metabolic profile but not with inflammation in the sick cows. Results indicate metabolic alterations, liver damage, and inflammation in LDA cows kept under small-scale farm conditions. Furthermore, the data suggest exacerbation of metabolic profile and Ca metabolism but not of inflammation and liver health with increasing lactation number and milk yield in cows affected by LDA

Shift of dietary carbohydrate source from milk to various solid feeds reshapes the rumen and fecal microbiome in calves

Abstract The transition from milk to solid diets drastically impacts the gut microbiome of calves. We explored the microbial communities of ruminal fluid and feces of Holstein calves when fed milk on d 7 of life, and when fed solid feeds based on either medium- or high-quality hay with or without concentrate inclusion (70% in fresh matter) on d 91. Ruminal fluid and feces had distinct microbial compositions already on d 7, showing that niche specialization in early-life gut is rather diet-independent. Changes between d 7 and d 91 were accompanied by a general increase in microbial diversity. Solid diets differed largely in their carbohydrate composition, being reflected in major changes on d 91, whereby concentrate inclusion was the main driver for differences among groups and strongly decreased microbial diversity in both matrices. Fecal enterotyping revealed two clusters: concentrate-supplemented animals had an enterotype prevalent in Prevotella, Succinivibrio and Anaerovibrio, whereas the enterotype of animals without concentrate was dominated by fibrolytic Ruminococcaceae. Hay quality also affected microbial composition and, compared to medium-quality, high-quality hay reduced alpha-diversity metrics. Concluding, our study revealed that concentrate inclusion, more than hay quality, dictates the establishment of niche-specific, microbial communities in the rumen and feces of calves

A meta-analysis of effects of chemical composition of incubated diet and bioactive compounds on in vitro ruminal fermentation

This study examined the role of supplementation of several bioactive compounds (BC) and the chemical composition of the diet used as substrate for in vitro incubations, on in vitro ruminal fermentation profile and nutrient degradation. A meta-analytical approach was used to weigh the sample size used in each experiment, and account for the random effect of each as well as unequal variance among studies. A total of 20 recently conducted experiments with 354 treatments, each including one control (i.e., no BC supplementation), fulfilled the criteria for inclusion. Doses of BC supplementation varied from 0.03 to 500 mg/g dry matter (DM) of incubated diet. Contents of crude protein (CP) and neutral detergent fibre (NDF) of the incubated diets (DM basis) ranged from 139 to 189 g/kg and 160 to 420 g/kg, respectively. Results indicate that supplementation of BC linearly decreased (137.4 versus 116.5 mmol/L; P<0.05) concentration of total volatile fatty acids (VFA) and proportion of acetate (P<0.05). Also, the concentration of ammonia in the in vitro rumen fluid was lower with BC supplementation (22.9 versus 15.6 mg/dL; P<0.05). Analysis by backward elimination correlation analysis revealed that inclusion of the chemical composition of the incubated diet into the model with BC supplementation improved the accuracy of estimation of responses of fermentation variables. Thus, higher NDF and CP contents of the substrate and higher BC dosage were associated with lower concentrations of total VFA (r2 = 0.54), whereas both lower CP contents of the substrate and BC supplementation lowered the concentration of ammonia (r2 = 0.32). This analysis showed negative associations between BC supplementation and in vitro disappearance of DM and NDF, and positive correlations with dietary NDF content. In contrast, higher BC inclusion and lowering NDF content in the diet was accompanied with decreased in vitro CH4 formation (r2 = 0.21). Results indicate that BC supplementation and chemical composition of the incubated diet are determining factors which impact responses of in vitro ruminal fermentation and degradation.This study examined the role of supplementation of several bioactive compounds (BC) and the chemical composition of the diet used as substrate for in vitro incubations, on in vitro ruminal fermentation profile and nutrient degradation. A meta-analytical approach was used to weigh the sample size used in each experiment, and account for the random effect of each as well as unequal variance among studies. A total of 20 recently conducted experiments with 354 treatments, each including one control (i.e., no BC supplementation), fulfilled the criteria for inclusion. Doses of BC supplementation varied from 0.03 to 500 mg/g dry matter (DM) of incubated diet. Contents of crude protein (CP) and neutral detergent fibre (NDF) of the incubated diets (DM basis) ranged from 139 to 189 g/kg and 160 to 420 g/kg, respectively. Results indicate that supplementation of BC linearly decreased (137.4 versus 116.5 mmol/L; P<0.05) concentration of total volatile fatty acids (VFA) and proportion of acetate (P<0.05). Also, the concentration of ammonia in the in vitro rumen fluid was lower with BC supplementation (22.9 versus 15.6 mg/dL; P<0.05). Analysis by backward elimination correlation analysis revealed that inclusion of the chemical composition of the incubated diet into the model with BC supplementation improved the accuracy of estimation of responses of fermentation variables. Thus, higher NDF and CP contents of the substrate and higher BC dosage were associated with lower concentrations of total VFA (r2 = 0.54), whereas both lower CP contents of the substrate and BC supplementation lowered the concentration of ammonia (r2 = 0.32). This analysis showed negative associations between BC supplementation and in vitro disappearance of DM and NDF, and positive correlations with dietary NDF content. In contrast, higher BC inclusion and lowering NDF content in the diet was accompanied with decreased in vitro CH4 formation (r2 = 0.21). Results indicate that BC supplementation and chemical composition of the incubated diet are determining factors which impact responses of in vitro ruminal fermentation and degradation

Metabolic Profile and Inflammatory Responses in Dairy Cows with Left Displaced Abomasum Kept under Small-Scaled Farm Conditions

Left displaced abomasum (LDA) is a severe metabolic disease of cattle with a strong negative impact on production efficiency of dairy farms. Metabolic and inflammatory alterations associated with this disease have been reported in earlier studies, conducted mostly in large dairy farms. This research aimed to: (1) evaluate metabolic and inflammatory responses in dairy cows affected by LDA in small-scaled dairy farms; and (2) establish an Animals 2015, 5 1022 association between lactation number and milk production with the outcome of metabolic variables. The cows with LDA had lower serum calcium (Ca), but greater concentrations of non-esterified fatty acids (NEFA) and beta-hydroxy-butyrate (BHBA), in particular when lactation number was &gt;2. Cows with LDA showed elevated levels of aspartate aminotransferase, glutamate dehydrogenase, and serum amyloid A (SAA), regardless of lactation number. In addition, this study revealed strong associations between milk yield and the alteration of metabolic profile but not with inflammation in the sick cows. Results indicate metabolic alterations, liver damage, and inflammation in LDA cows kept under small-scale farm conditions. Furthermore, the data suggest exacerbation of metabolic profile and Ca metabolism but not of inflammation and liver health with increasing lactation number and milk yield in cows affected by LDA

Correction: Temporal dynamics of in-situ fiber-adherent bacterial community under ruminal acidotic conditions determined by 16S rRNA gene profiling.

[This corrects the article DOI: 10.1371/journal.pone.0182271.]