Metabolism of polyunsaturated fatty acids and their toxicity to the microflora of the rumen

Residual feed intake in beef cattle and its association with carcass traits, ruminal solid-fraction bacteria, and epithelium gene expression

Background

Residual feed intake (RFI) describes an animal’s feed efficiency independent of growth performance. The objective of this study was to determine differences in growth performance, carcass traits, major bacteria attached to ruminal solids-fraction, and ruminal epithelium gene expression between the most-efficient and the least-efficient beef cattle. One-hundred and forty-nine Red Angus cattle were allocated to three contemporary groups according to sex and herd origin. Animals were fed a finishing diet in confinement for 70 d to determine the RFI category for each. Within each group, the two most-efficient (n = 6; RFI coefficient = − 2.69 ± 0.58 kg dry matter intake (DMI)/d) and the two least-efficient animals (n = 6; RFI coefficient = 3.08 ± 0.55 kg DMI/d) were selected. Immediately after slaughter, ruminal solids-fraction and ruminal epithelium were collected for bacteria relative abundance and epithelial gene expression analyses, respectively, using real-time PCR.

Results

The most-efficient animals consumed less feed (P = 0.01; 5.03 kg less DMI/d) compared with the least-efficient animals. No differences (P > 0.10) in initial body weight (BW), final BW, and average daily gain (ADG) were observed between the two RFI classes. There were no significant RFI × sex effects (P > 0.10) on growth performance. Compared with the least-efficient group, hot carcass weight (HCW), ribeye area (REA), and kidney, pelvic, and heart fat (KPH) were greater (P ≤ 0.05) in the most-efficient cattle. No RFI × sex effect (P > 0.10) for carcass traits was detected between RFI groups. Of the 10 bacterial species evaluated, the most-efficient compared with least efficient cattle had greater (P ≤ 0.05) relative abundance of Eubacterium ruminantium, Fibrobacter succinogenes, and Megasphaera elsdenii, and lower (P ≤ 0.05) Succinimonas amylolytica and total bacterial density. No RFI × sex effect on ruminal bacteria was detected between RFI groups. Of the 34 genes evaluated in ruminal epithelium, the most-efficient cattle had greater (P ≤ 0.05) abundance of genes involved in VFA absorption, metabolism, ketogenesis, and immune/inflammation-response. The RFI × sex interactions indicated that responses in gene expression between RFI groups were due to differences in sex. Steers in the most-efficient compared with least-efficient group had greater (P ≤ 0.05) expression of SLC9A1, HIF1A, and ACO2. The most-efficient compared with least-efficient heifers had greater (P ≤ 0.05) mRNA expression of BDH1 and lower expression (P ≤ 0.05) of SLC9A2 and PDHA1.

Conclusions

The present study revealed that greater feed efficiency in beef cattle is associated with differences in bacterial species and transcriptional adaptations in the ruminal epithelium that might enhance nutrient delivery and utilization by tissues. The lack of RFI × sex interaction for growth performance and carcass traits indicates that sex may not play a major role in improving these phenotypes in superior RFI beef cattle. However, it is important to note that this result should not be considered a solid biomarker of efficient beef cattle prior to further examination due to the limited number of heifers compared with steers used in the study.

Electronic supplementary material

The online version of this article (10.1186/s40104-018-0283-8) contains supplementary material, which is available to authorized users.

Enzymatic Study of Linoleic and Alpha-Linolenic Acids Biohydrogenation by Chloramphenicol-Treated Mixed Rumen Bacterial Species

In the rumen, dietary polyunsaturated fatty acids (PUFA) are reduced by a multistage reaction called biohydrogenation (BH). BH leads to a high proportion of saturated fat in ruminant products, but also products some potential bioactive intermediates like conjugated linoleic and linolenic acids. BH is composed of two kinds of reactions: first an isomerization of PUFA followed by reductions (two for linoleic acid, C18:2n-6; three for α-linolenic acid, C18:3n-3). There is little knowledge about BH enzymes as BH bacterial species are the subject of a lot of studies. Nevertheless, both aspects must be explored to control BH and enhance the fatty acids profile of ruminant products. In the present study, an alternative approach was developed to study the enzymes produced in vivo by mixed ruminal bacteria, using inactivation of bacteria by chloramphenicol, an inhibitor of protein synthesis in prokaryotes, before in vitro incubation. To study C18:2n-6 and C18:3n-3 BH several experiments were used: (1) with different incubation durations (0 to 3) to estimate average rates and efficiencies of all BH reactions, and intermediates production; and (2) with different initial quantities of PUFA (0.25 to 2 mg) to estimate Michaelis–Menten enzymatic parameters, K_m and V_max. A last experiment explored the effect of pH buffer and donor cow diet on C18:2n-6 isomerization pathways. Concerning C18:2n-6 BH, this study confirmed the high saturability of its isomerization, the inhibition of both trans11 and trans10 pathways by a low pH, and the last reduction to stearic acid as the limiting-step. Concerning C18:3n-3, its BH was faster than C18:2n-6, in particular its isomerization (V_max = 3.4 vs. 0.6 mM/h, respectively), and the limiting-step was the second reduction to t11-C18:1. Besides, our mixed isomerases had a higher affinity for C18:2n-6 than for C18:3n-3 (K_m = 2.0 × 10^-3 vs. 4.3 × 10^-3 M, respectively), but due to their high saturability by C18:2n-6, they had a lower efficiency to isomerize C18:2n-6 than C18:3n-3. Chloramphenicol-treated ruminal fluid would be a meaningful method to study the BH enzymes activities.

Differential effects of oilseed supplements on methane production and milk fatty acid concentrations in dairy cows

It is known that supplementing dairy cow diets with full-fat oilseeds can be used as a strategy to mitigate methane emissions, through their action on rumen fermentation. However, direct comparisons of the effect of different oil sources are very few, as are studies implementing supplementation levels that reflect what is commonly fed on commercial farms. The objective was to investigate the effect of feeding different forms of supplemental plant oils on both methane emissions and milk fatty acid (FA) profile. Four multiparous, Holstein-Friesian cows in mid-lactation were randomly allocated to one of four treatment diets in a 4×4 Latin square design with 28-day periods. Diets were fed as a total mixed ration with a 50 : 50 forage : concentrate ratio (dry matter (DM) basis) with the forage consisting of 75 : 25 maize silage : grass silage (DM). Dietary treatments were a control diet containing no supplemental fat, and three treatment diets containing extruded linseed (EL), calcium salts of palm and linseed oil (CPLO) or milled rapeseed (MR) formulated to provide each cow with an estimated 500 g additional oil/day (22 g oil/kg diet DM). Dry matter intake (DMI), milk yield, milk composition and methane production were measured at the end of each experimental period when cows were housed in respiration chambers for 4 days. There was no effect of treatment diet on DMI or milk protein or lactose concentration, but oilseed-based supplements increased milk yield compared with the control diet and milk fat concentration relative to control was reduced by 4 g/kg by supplemental EL. Feeding CPLO reduced methane production, and both linseed-based supplements decreased methane yield (by 1.8 l/kg DMI) and intensity (by 2.7 l/kg milk yield) compared with the control diet, but feeding MR had no effect on methane emission. All the fat supplements decreased milk total saturated fatty acid (SFA) concentration compared with the control, and SFA were replaced with mainly cis-9 18:1 but also trans FA (and in the case of EL and CPLO there were increases in polyunsaturated FA concentration). Supplementing dairy cow diets with these oilseed-based preparations affected milk FA profile and increased milk yield. However, only the linseed-based supplements reduced methane production, yield or intensity, whereas feeding MR had no effect.

Symposium review: Understanding diet-microbe interactions to enhance productivity of dairy cows

Ruminants are dependent on the microbiota (bacteria, protozoa, archaea, and fungi) that inhabit the reticulo-rumen for digestion of feedstuffs. Nearly 70% of energy and 50% of protein requirements for dairy cows are met by microbial fermentation in the rumen, emphasizing the need to characterize the role of microbes in feed breakdown and nutrient utilization. Over the past 2 decades, next-generation sequencing technologies have allowed for rapid expansion of knowledge concerning microbial populations and alterations in response to forages, concentrates, supplements, and probiotics in the rumen. Advances in gene sequencing and emerging bioinformatic tools have allowed for increased throughput of data to aid in our understanding of the functional relevance of microbial genomes. In particular, metagenomics can identify specific genes involved in metabolic pathways, and metatranscriptomics can describe the transcriptional activity of microbial genes. These powerful approaches help untangle the complex interactions between microbes and dietary nutrients so that we can more fully understand the physiology of feed digestion in the rumen. Application of genomics-based approaches offers promise in unraveling microbial niches and respective gene repertoires to potentiate fiber and nonfiber carbohydrate digestion, microbial protein synthesis, and healthy biohydrogenation. New information on microbial genomics and interactions with dietary components will more clearly define pathways in the rumen to positively influence milk yield and components.

Effects of Condensed and Hydrolyzable Tannins on Rumen Metabolism with Emphasis on the Biohydrogenation of Unsaturated Fatty Acids

The hypothesis that condensed tannins have higher inhibitory effect on ruminal biohydrogenation than hydrolyzable tannins was tested. Condensed tannin extract from mimosa (CT) and hydrolyzable tannin extract from chestnut (HT) or their mixture (MIX) were incorporated (10%) into oil supplemented diets and fed to rumen fistulated sheep. Fatty acid and dimethyl acetal composition of rumen contents and bacterial biomass were determined. Selected rumen bacteria were analyzed by quantitative real time PCR. Lower ( P < 0.05) rumen volatile fatty acids concentrations were observed with CT compared to HT. Moreover, lower concentration ( P < 0.05) of Fibrobacter succinogenes, Ruminococcus flavefaciens, Ruminococcus albus, and Butyrivibrio proteoclasticus were observed with CT compared to HT. The extension of biohydrogenation of 18:2n-6 and 18:3n-3 did not differ among treatments but was much more variable with CT and MIX than with HT. The trans-/ cis-18:1 ratio in bacterial biomass was higher ( P < 0.05) with HT than CT. Thus, mimosa condensed tannins had a higher inhibitory effect on ruminal metabolism and biohydrogenation than chestnut hydrolyzable tannins.

Effects of fat supplementation to diets high in nonforage fiber on production responses of midlactation dairy cows

The effects of dietary nonforage fiber sources on production responses of lactating dairy cattle have been well described, but interactions with other components of the diet have been less thoroughly explored. We investigated the effects of adding 2 commonly fed fat sources to a ration featuring high levels of nonforage fiber supplied by a corn milling by-product. Midlactation Holstein cows were blocked by parity, stratified by days in milk, and randomly assigned to 1 of 6 pens (12 cows/pen). Pens were randomly assigned to treatment sequences in a 3 × 3 Latin square design, where the treatments consisted of prilled saturated fat (SAT; Energy Booster 100, Milk Specialties Co., Dundee, IL), calcium salts of long-chain fatty acids (UNS; Megalac, Church and Dwight Co. Inc., Princeton, NJ), or no added dietary fat (control), with fat sources included to provide 1.2% added fat (dry matter basis). Treatment periods were 21 d; milk and feed samples were collected and milk yield and feed intake were recorded for the last 4 d of each period. Results were analyzed with mixed models with pen as the experimental unit, and orthogonal contrasts were employed to evaluate the overall effect of added fat and the effect of fat source. Dry matter intake and milk yield tended to increase with added fat. Protein content decreased with fat supplementation, to a greater degree for UNS than for SAT, but protein yield was not affected. Fat content, fat yield, and energy-corrected milk yield were not affected by treatment. Conversion of feed to milk tended to increase for UNS compared with SAT. Fat supplementation to diets high in nonforage fiber had effects that were similar to those reported for more traditional lactation diets, except for the dry matter intake response.

Rumen Biohydrogenation and Microbial Community Changes Upon Early Life Supplementation of 22:6n-3 Enriched Microalgae to Goats

Dietary supplementation of docosahexaenoic acid (DHA)-enriched products inhibits the final step of biohydrogenation in the adult rumen, resulting in the accumulation of 18:1 isomers, particularly of trans(t)-11 18:1. Occasionally, a shift toward the formation of t10 intermediates at the expense of t11 intermediates can be triggered. However, whether similar impact would occur when supplementing DHA-enriched products during pregnancy or early life remains unknown. Therefore, the current in vivo study aimed to investigate the effect of a nutritional intervention with DHA in the early life of goat kids on rumen biohydrogenation and microbial community. Delivery of DHA was achieved by supplementing DHA-enriched microalgae (DHA Gold) either to the maternal diet during pregnancy (prenatal) or to the diet of the young offspring (postnatal). At the age of 12 weeks, rumen fluid was sampled for analysis of long-chain fatty acids and microbial community based on bacterial 16S rRNA amplicon sequencing. Postnatal supplementation with DHA-enriched microalgae inhibited the final biohydrogenation step, as observed in adult animals. This resulted particularly in increased ruminal proportions of t11 18:1 rather than a shift to t10 intermediates, suggesting that both young and adult goats might be less prone to dietary induced shifts toward the formation of t10 intermediates, in comparison with cows. Although Butyrivibrio species have been identified as the most important biohydrogenating bacteria, this genus was more abundant when complete biohydrogenation, i.e. 18:0 formation, was inhibited. Blautia abundance was positively correlated with 18:0 accumulation, whereas Lactobacillus spp. Dialister spp. and Bifidobacterium spp. were more abundant in situations with greater t10 accumulation. Extensive comparisons made between current results and literature data indicate that current associations between biohydrogenation intermediates and rumen bacteria in young goats align with former observations in adult ruminants.

Effects of partially replacing barley with sugar beet pulp, with and without roasted canola seeds, on performance, rumen histology and fermentation patterns in finishing Arabian lambs

This study investigated the effects of partially replacing barley grains with sugar beet pulp (SBP), with and without roasted canola seed (RCS) on ruminal pH, ruminal volatile fatty acid (VFA) concentrations, ruminal histomorphometric characteristics, and performance in finishing lambs fed a high concentrate diet. Twenty-four Arabian male lambs (23.7 ± 2.5 kg bodyweight, 118 ± 10 days in age) were used for 99 days in a completely randomised design with a 2 × 2 factorial arrangement. Lambs were fed with a high concentrate diet containing (1) 68% barley (B) (2) barley plus 7% RCS (B + RCS) (3) 36% SBP, (4) SBP plus 7% RCS (SBP + RCS). Ruminal fluid pH and VFA concentrations were determined at 0, 2, 4 and 8 h post-feeding 1 day before slaughter day. Tissue samples were collected for histomorphometric study at slaughter day. Average daily gain of the lambs was not affected by partial replacement of barley with SBP, however it was improved by RCS inclusion (P < 0.05). Diets with RCS had significantly lower (P < 0.05) neutral detergent fibre and acid detergent fibre digestibility values than diets without RCS (P < 0.05). Both SBP and RCS increased ruminal pH, molar proportions of acetate, isobutyrate but decreased molar proportion of propionate in rumen content (P < 0.05). The height, width, epithelial thickness and tunica muscularis of rumen papilla and reticulum folds were increased by SBP (P < 0.05). Density of reticulum folds were higher in lambs fed by higher SBP (P < 0.05). Inclusion of RCS significantly increased papillae height and thickness of epithelium (P < 0.05). In conclusion, partially replacing barley with SBP as well as RCS inclusion prevented a drop in the ruminal pH, and improved the morphology of the rumen-reticulum in finishing lambs fed a high concentrate diet.

Production, milk and plasma fatty acid profile, and nutrient utilization in Jersey cows fed flaxseed oil and corn grain with different particle size

We aimed to compare the effects of ground (GC) or cracked corn (CC), with or without flaxseed oil (FSO), on milk yield, milk and plasma fatty acid (FA) profile, and nutrient digestibility in Jersey cows fed diets formulated to contain similar starch concentrations. Twelve multiparous organic-certified Jersey cows averaging (mean ± standard deviation) 455 ± 41.9 kg of body weight and 152 ± 34 d in milk and 4 primiparous organic-certified Jersey cows averaging (mean ± standard deviation) 356 ± 2.41 kg of body weight and 174 ± 30 d in milk in the beginning of the experiment were used. Cows were randomly assigned to treatment sequences in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Each period lasted 24 d with 18 d for diet adaptation and 6 d for data and sample collection. Treatments were fed as total mixed rations consisting of (dry matter basis): (1) 0% FSO + 27.1% GC, (2) 0% FSO + 28.3% CC, (3) 3% FSO + 27.1% GC, and (4) 3% FSO + 28.3% CC. All cows were offered 55% of the total diet dry matter as mixed grass-legume baleage and treatments averaged 20% starch. Significant FSO × corn grain particle size interactions were observed for some variables including milk concentration of lactose and proportions of cis-9,cis-12,cis-15 18:3 in milk and plasma. The proportion of cis-9,cis-12,cis-15 18:3 in milk and plasma decreased slightly when comparing GC versus CC in 0% FSO cows, but a larger reduction was observed in 3% FSO cows. Dry matter intake did not differ and averaged 16.1 kg/d across diets. Feeding 3% FSO increased yields of milk and milk fat and lactose and feed and milk N efficiencies, but decreased fat, true protein, and MUN concentrations and apparent total-tract digestibility of fiber. The Σ branched-chain, Σ<16C, Σ16C, and Σn-6 FA decreased, whereas Σ18C, Σcis-18:1, and Σtrans-18:1 FA increased in 3% versus 0% FSO cows. No effect of corn particle size was observed for production and milk components. However, the apparent total-tract digestibility of starch was greater in GC than CC cows. Compared with CC, GC increased Σ branched-chain, Σ<16C, Σ16C, Σn-6 FA, and decreased Σ18C and Σ cis-18:1 FA in milk fat. Overall, results of this study are more directly applicable to dairy cows fed low starch, mixed grass-legume baleage-based diets.

Dietary Alfalfa and Calcium Salts of Long-Chain Fatty Acids Alter Protein Utilization, Microbial Populations, and Plasma Fatty Acid Profile in Holstein Freemartin Heifers

This study presented the effects of alfalfa and calcium salts of long-chain fatty acids (CSFA) on feed intake, apparent digestibility, rumen fermentation, microbial community, plasma biochemical parameters, and fatty acid profile in Holstein freemartin heifers. Eight Holstein freemartin heifers were randomly divided into a 4 × 4 Latin Square experiment with 2 × 2 factorial diets, with or without alfalfa or CSFA. Dietary supplementation of CSFA significantly increased the apparent digestibility of dry matter, crude protein, neutral detergent fiber, organic matter, and significantly reduced N retention (P < 0.05). CSFA increased the concentration of ammonia nitrogen in the ruminal fluid (P < 0.05), but alfalfa increased the concentration of valerate and isovalerate (P < 0.05). CSFA increased the concentration of ammonia nitrogen and the relative population of Streptococcus bovis in the rumen (P < 0.05) and inhibited the relative population of Ruminococcus flavefaciens, methanogens, and protozoa (P < 0.05). Alfalfa instead of Leymus chinensis increased the relative population of Butyrivibrio fibrisolvens and Ruminobacter amylophilus in the rumen (P < 0.05) and reduced the relative population of the Ruminococcus albus and Megasphaera elsdenii (P < 0.05). Supplemental CSFA increased the concentration of cholesterol and low-density lipoprotein cholesterol in the plasma (P < 0.05). And it also altered the composition of fatty acids in the plasma, which was expressed in reducing saturated fatty acid (ΣSFA) ratio and C14-C17 fatty acids proportion except C16:0 (P < 0.05) and increasing the proportion of polyunsaturated fatty acid (ΣPUFA) and unsaturated fatty acid (ΣUFA) (P < 0.05). The results showed that alfalfa and CSFA had interaction effect on the apparent digestibility of ether extracts, plasma triglyceride concentration, isobutyrate concentration, and Ruminococcus albus relative abundance in the rumen. It was concluded that alfalfa substituting Leymus chinensis did not change the apparent digestibility of nutrients in the final stage of fattening Holstein freemartin heifers, while CSFA increased the cholesterol and the proportion of unsaturated fatty acids in plasma. Alfalfa and CSFA had mutual interaction effect on fat digestion and plasma triglycerides.

Effect of partially replacing a barley-based concentrate with flaxseed-based products on the rumen bacterial population of lactating Holstein dairy cows

AIMS

The effects of partial replacement of a barley-based concentrate with flaxseed-based products on the rumen bacterial population of lactating Holstein dairy cows were evaluated.

METHODS AND RESULTS

Treatments fed were CONT, a normal diet that included barley silage, alfalfa hay and a barley-based concentrate that contained no flaxseed or faba beans; FLAX, inclusion of a nonextruded flaxseed-based product containing 55·0% flaxseed, 37·8% field peas and 6·9% alfalfa; EXT, similar to FLAX, but the product was extruded and EXTT, similar to FLAX, but product was extruded and field peas were replaced by high-tannin faba beans. The rumen bacterial population was evaluated by utilizing 16S rRNA gene sequencing. Most abundant phyla, families and genera were unaffected. However, some taxa were affected; for example, unsaturated fatty acid content was negatively correlated with Clostridiaceae, and tannin content was negatively correlated with BS11 and Paraprevotellaceae.

CONCLUSIONS

Predominant rumen bacterial taxa were not affected, but the abundance of some taxa found in lower proportions shifted, possibly due to sensitivity to unsaturated fatty acids or tannins.

SIGNIFICANCE AND IMPACT OF THE STUDY

Flaxseed-based products were effective for partially replacing barley-based concentrate in rations of lactating dairy cows. No negative effects of these products were observed on the abundance of predominant rumen bacterial taxa, with only minor shifts in less abundant bacteria.

Effects of partial replacement of maize in the diet with crude glycerin and/or soyabean oil on ruminal fermentation and microbial population in Nellore steers

The objective of this study was to determine whether a combination of crude glycerin (CG) and soyabean oil (SO) could be used to partially replace maize in the diet of Nellore steers while maintaining optimum feed utilisation. Eight castrated Nellore steers fitted with ruminal and duodenal cannulas were used in a double 4×4 Latin square design balanced for residual effects, in a factorial arrangement (A×B), when factor A corresponded to the provision of SO, and factor B to the provision of CG. Steers feed SO and CG showed similar DM intake, DM, organic matter and neutral-detergent fibre digestibility to that of steers fed diets without oil and without glycerine (P>0·05). Both diets with CG additions reduced the acetate:propionate ratio and increased the proportion of iso-butyrate, butyrate, iso-valerate and valerate (P<0·05). Steers fed diets containing SO had less total N excretion (P<0·001) and showed greater retained N expressed as % N intake (P=0·022). SO and CG diet generated a greater ruminal abundance of Prevotella, Succinivibrio, Ruminococcus, Syntrophococcus and Succiniclasticum. Archaea abundance (P=0·002) and total ciliate protozoa were less in steers fed diets containing SO (P=0·011). CG associated with lipids could be an energy source, which is a useful strategy for the partial replacement of maize in cattle diets, could result in reduced total N excretion and ruminal methanogens without affecting intake and digestibility.

Endocannabinoid concentrations in plasma during the finishing period are associated with feed efficiency and carcass composition of beef cattle

We previously have shown that plasma concentrations of endocannabinoids (EC) are positively correlated with feed efficiency and leaner carcasses in finishing steers. However, whether the animal growth during the finishing period affects the concentration of EC is unknown. The objective of this study was to quantify anandamide (AEA) and 2-arachidonyl glycerol (2-AG) in plasma during different stages of the finishing period and identify possible associations with production traits and carcass composition in beef calves. Individual DMI and BW gain were measured on 236 calves ( = 127 steers and = 109 heifers) for 84 d on a finishing ration. Blood samples were collected on d 0 (early), 42 (mid), and 83 (late) of days on study (DOS). Cattle were slaughtered 44 d after the feeding study. Plasma concentration of AEA at 0 DOS was indirectly associated with the G:F ( < 0.01) and directly associated with residual feed intake (RFI; < 0.05) in steers. In contrast, plasma concentration of AEA at 83 DOS was directly associated with the G:F and indirectly associated RFI in heifers and steers ( < 0.01). In addition, AEA concentration at 42 and 83 DOS was positively associated with ADG and DMI ( < 0.01) in heifers and steers. Furthermore, 2-AG concentration at 42 DOS was positively associated with ADG in steers ( < 0.01) and heifers ( < 0.10). Plasma concentration of AEA was positively associated ( < 0.05) with HCW, USDA-calculated yield grade, and 12th-rib fat thickness in heifers, whereas no associations were found in steers. In contrast, 2-AG concentration was not associated with any carcass traits. These results provide evidence that circulating EC change during animal growth and that AEA concentration may be a useful predictor of growth and feed efficiency and, in females, of carcass attributes.

Camelina Seed Supplementation at Two Dietary Fat Levels Change Ruminal Bacterial Community Composition in a Dual-Flow Continuous Culture System

This experiment aimed to determine the effects of camelina seed (CS) supplementation at different dietary fat levels on ruminal bacterial community composition and how it relates to changes in ruminal fermentation in a dual-flow continuous culture system. Diets were randomly assigned to 8 fermenters (1,200–1,250 mL) in a 2 × 2 factorial arrangement of treatments in a replicated 4 × 4 Latin square with four 10-day experimental periods that consisted of 7 days for diet adaptation and 3 days for sample collection. Treatments were: (1) no CS at 5% ether extract (EE, NCS5); (2) no CS at 8% EE (NCS8); (3) 7.7% CS at 5% EE (CS5); and (4) 17.7% CS at 8% EE (CS8). Megalac was used as a control to adjust EE levels. Diets contained 55% orchardgrass hay and 45% concentrate, and fermenters were equally fed a total of 72 g/day (DM basis) twice daily. The bacterial community was determined by sequencing the V4 region of the 16S rRNA gene using the Illumina MiSeq platform. Sequencing data were analyzed using mothur and statistical analyses were performed in R and SAS. The most abundant phyla across treatments were the Bacteroidetes and Firmicutes, accounting for 49 and 39% of the total sequences, respectively. The bacterial community composition in both liquid and solid fractions of the effluent digesta changed with CS supplementation but not by dietary EE. Including CS in the diets decreased the relative abundances of Ruminococcus spp., Fibrobacter spp., and Butyrivibrio spp. The most abundant genus across treatments, Prevotella, was reduced by high dietary EE levels, while Megasphaera and Succinivibrio were increased by CS supplementation in the liquid fraction. Correlatively, the concentration of acetate was decreased while propionate increased; C18:0 was decreased and polyunsaturated fatty acids, especially C18:2 n-6 and C18:3 n-3, were increased by CS supplementation. Based on the correlation analysis between genera and fermentation end products, this study revealed that CS supplementation could be energetically beneficial to dairy cows by increasing propionate-producing bacteria and suppressing ruminal bacteria associated with biohydrogenation. However, attention should be given to avoid the effects of CS supplementation on suppressing cellulolytic bacteria.

Contribution of Ruminal Fungi, Archaea, Protozoa, and Bacteria to the Methane Suppression Caused by Oilseed Supplemented Diets

Dietary lipids can suppress methane emission from ruminants, but effects are variable. Especially the role of bacteria, archaea, fungi and protozoa in mediating the lipid effects is unclear. In the present in vitro study, archaea, fungi and protozoa were selectively inhibited by specific agents. This was fully or almost fully successful for fungi and protozoa as well as archaeal activity as determined by the methyl-coenzyme M reductase alpha subunit gene. Five different microbial treatments were generated: rumen fluid being intact (I), without archaea (–A), without fungi (–F), without protozoa (–P) and with bacteria only (–AFP). A forage-concentrate diet given alone or supplemented with crushed full-fat oilseeds of either safflower (Carthamus tinctorius) or poppy (Papaver somniferum) or camelina (Camelina sativa) at 70 g oil kg⁻¹ diet dry matter was incubated. This added up to 20 treatments with six incubation runs per treatment. All oilseeds suppressed methane emission compared to the non-supplemented control. Compared to the non-supplemented control, –F decreased organic matter (OM) degradation, and short-chain fatty acid concentration was greater with camelina and safflower seeds. Methane suppression per OM digested in –F was greater with camelina seeds (−12 vs.−7% with I, P = 0.06), but smaller with poppy seeds (−4 vs. −8% with I, P = 0.03), and not affected with safflower seeds. With –P, camelina seeds decreased the acetate-to-propionate ratio and enhanced the methane suppression per gram dry matter (18 vs. 10% with I, P = 0.08). Hydrogen recovery was improved with –P in any oilseeds compared to non-supplemented control. No methane emission was detected with the –A and –AFP treatments. In conclusion, concerning methanogenesis, camelina seeds seem to exert effects only on archaea and bacteria. By contrast, with safflower and poppy seeds methane was obviously reduced mainly through the interaction with protozoa or archaea associated with protozoa. This demonstrated that the microbial groups differ in their contribution to the methane suppressing effect dependent on the source of lipid. These findings help to understand how lipid supplementation and microbial groups interact, and thus may assist in making this methane mitigation tool more efficient, but await confirmation in vivo.

Can we improve the nutritional quality of meat?

The nutritional value of meat is an increasingly important factor influencing consumer preferences for poultry, red meat and processed meat products. Intramuscular fat content and composition, in addition to high quality protein, trace minerals and vitamins are important determinants of nutritional value. Fat content of meat at retail has decreased substantially over the past 40 years through advances in animal genetics, nutrition and management and changes in processing techniques. Evidence of the association between diet and the incidence of human non-communicable diseases has driven an interest in developing production systems for lowering total SFA and trans fatty acid (TFA) content and enrichment of n-3 PUFA concentrations in meat and meat products. Typically, poultry and pork has a lower fat content, containing higher PUFA and lower TFA concentrations than lamb or beef. Animal genetics, nutrition and maturity, coupled with their rumen microbiome, are the main factors influencing tissue lipid content and relative proportions of SFA, MUFA and PUFA. Altering the fatty acid (FA) profile of lamb and beef is determined to a large extent by extensive plant and microbial lipolysis and subsequent microbial biohydrogenation of dietary lipid in the rumen, and one of the major reasons explaining the differences in lipid composition of meat from monogastrics and ruminants. Nutritional strategies can be used to align the fat content and FA composition of poultry, pork, lamb and beef with Public Health Guidelines for lowering the social and economic burden of chronic disease.

Effect of unconventional oilseeds (safflower, poppy, hemp, camelina) on in vitro ruminal methane production and fermentation

BACKGROUND

Dietary supplementation with oilseeds can reduce methane emission in ruminants, but only a few common seeds have been tested so far. This study tested safflower (Carthamus tinctorius), poppy (Papaver somniferum), hemp (Cannabis sativa), and camelina (Camelina sativa) seeds in vitro using coconut (Cocos nucifera) oil and linseed (Linum usitatissimum) as positive controls.

RESULTS

All the tested oilseeds suppressed methane yield (mL g^-1 dry matter, up to 21%) compared to the non-supplemented control when provided at 70 g oil kg^-1 dry matter, and they were as effective as coconut oil. Safflower and hemp were more effective than linseed (21% and 18% vs. 10%), whereas the effects of poppy and camelina were similar to linseed. When methane was related to digestible organic matter, only hemp and safflower seeds and coconut oil were effective compared to the non-supplemented control (up to 11%). The level of methanogenesis and the ratios of either the n-6:n-3 fatty acids or C_18:2 :C_18:3 in the seed lipids were not related.

CONCLUSION

Unconventional oilseeds widen the spectrum of oilseeds that can be used in dietary methane mitigation. In vivo confirmation of their methane mitigating effect is still needed, and their effects on animal performance still must be determined. © 2017 Society of Chemical Industry.

Increasing corn distillers solubles alters the liquid fraction of the ruminal microbiome

Five ruminally fistulated steers were used in a 5 × 5 Latin square design to determine the effects of increasing dietary fat and sulfur from condensed distiller's solubles (CDS) on the ruminal microbiome. Treatments included a corn-based control (CON) and 4 levels of CDS (0, 10, 19, and 27%) in a coproduct-based (corn gluten feed and soybean hulls) diet. Fat concentrations were 1.79, 4.43, 6.80, and 8.91% for diets containing 0, 10, 19, and 27% CDS, respectively. Steers were fed for ad libitum intake once daily. After feeding each diet for 18 d, ruminal samples were collected 3 h after feeding on d 19. Samples were separated into solid and liquid fractions. Microbial DNA was extracted for bacterial analysis using paired-end sequencing of the V3 through V4 region of the 16S rRNA gene on the MiSeq Illumina platform and quantitative PCR of selected species. Orthogonal contrasts were used to determine linear and quadratic effects of CDS inclusion. Increasing CDS inclusion decreased (linear, < 0.05) α-diversity and species richness in the liquid fraction. Analysis of Bray-Curtis similarity indicated a treatment effect ( = 0.01) in the liquid fraction. At the phyla level, relative abundance of Bacteroidetes decreased in steers fed increasing dietary inclusion of CDS as Firmicutes increased to 82% of sequences for the 27% CDS treatment. Family Ruminococcaceae increased (linear, < 0.01) 2-fold in the liquid fraction when feeding CDS increased from 0 to 27% CDS, yet genera tended ( = 0.09) to decrease in steers fed greater CDS. The most abundant family of sulfate-reducing bacteria, Desulfovibrionaceae, increased ( < 0.03) in the solid and liquid fraction in steers fed additional dietary CDS and sulfur. Relative abundance of family Veillonellaceae and were increased (linear, ≤ 0.02) in the solid fraction as steers were fed increasing CDS. There were no effects ( > 0.10) of feeding increasing dietary fat from CDS on fibroylytic genus in either fraction. Results demonstrate increasing fat and sulfur from CDS in a coproduct-based diet markedly alters the liquid fraction ruminal microbiome but does not elicit negative effects on relative abundance of identified fiber-fermenting bacteria.

Fatty acids, vitamins and cholesterol content, and sensory properties of cheese made with milk from sheep fed rapeseed oilcake

The aim of the present study was to evaluate the influence of rapeseed oilcake used for feeding sheep on the content of fatty acids (FA), tocopherols, retinoids, and cholesterol of milk and cheese, and on the sensory properties of cheese. Indoor animal feeding (in winter) is the highest cost of production for cheesemakers, and the inclusion of locally produced rapeseed oilcake in the concentrate feed formulation can reduce the cost of cheese production, as long as the quality of the cheese is not altered. The experiment was carried out in March (mid lactation) with 72 Latxa sheep from an experimental farm located in the Basque Country (northern Spain). Two homogeneous groups of animals (n = 36) were set to receive each a different diet based on commercial or rapeseed concentrate, respectively, and forage (Festuca hay). Animal production parameters were individually recorded for each feeding group, whereas bulk milk from each group was used for cheesemaking trials. The rapeseed concentrate had higher amounts of unsaturated FA (mainly C18:1 cis isomers, C18:2 cis-9,cis-12 and C18:3 cis-9,cis-12,cis-15) and tocopherols than the commercial concentrate. The inclusion of rapeseed oilcake in the diet of dairy sheep did not compromise animal production parameters or milk gross composition. Bulk milk and cheese from sheep fed rapeseed concentrate showed higher content of unsaturated FA and tocopherols than those from sheep fed commercial concentrate. No differences were observed in the content of retinoid in milk and cheese between feeding groups, whereas the cholesterol content was slightly lower in cheese made with milk from sheep fed rapeseed concentrate. Thus, milk and cheese from sheep fed rapeseed concentrate had a healthier lipid profile. In addition, the inclusion of rapeseed oilcake in the diet of sheep did not change the typical sensory attributes of Protected Denomination of Origin Idiazabal cheese. Therefore, rapeseed concentrate could be a good local resource for feeding sheep to improve the nutritional quality of dairy products and to provide higher returns to farms.

Dose-response effects of dietary pequi oil on fermentation characteristics and microbial population using a rumen simulation technique (Rusitec)

The effect of increasing the concentration of commercial pequi (Caryocar brasiliense) oil on fermentation characteristics and abundance of methanogens and fibrolityc bacteria was evaluated using the rumen simulation technique (Rusitec). In vitro incubation was performed over 15 days using a basal diet consisting of ryegrass, maize silage and concentrate in equal proportions. Treatments consisted of control diet (no pequi oil inclusion, 0 g/kg DM), pequi dose 1 (45 g/kg DM), and pequi dose 2 (91 g/kg DM). After a 7 day adaptation period, samples for fermentation parameters (total gas, methane, and VFA production) were taken on a daily basis. Quantitative real time PCR (q-PCR) was used to evaluate the abundance of the main rumen cellulolytic bacteria, as well as abundance of methanogens. Supplementation with pequi oil did not reduce overall methane production (P = 0.97), however a tendency (P = 0.06) to decrease proportion of methane in overall microbial gas was observed. Increasing addition of pequi oil was associated with a linear decrease (P < 0.01) in dry matter disappearance of maize silage. The abundance of total methanogens was unchanged by the addition of pequi oil, but numbers of those belonging to Methanomassiliicoccaceae decreased in liquid-associated microbes (LAM) samples (P < 0.01) and solid-associated microbes (SAM) samples (P = 0.09) respectively, while Methanobrevibacter spp. increased (P < 0.01) only in SAM samples. Fibrobacter succinogenes decreased (P < 0.01) in both LAM and SAM samples when substrates were supplemented with pequi oil. In conclusion, pequi oil was ineffective in mitigating methane emissions and had some adverse effects on digestibility and selected fibrolytic bacteria.

In vitro response to EPA, DPA, and DHA: Comparison of effects on ruminal fermentation and biohydrogenation of 18-carbon fatty acids in cows and ewes

The modulation of milk fat nutritional quality through fish oil supplementation seems to be largely explained by the action of n-3 very long chain polyunsaturated fatty acids (PUFA) on ruminal biohydrogenation (BH) of C18 fatty acids (FA). However, relationships among this action, disappearance of those PUFA in the rumen, and potential detrimental consequences on ruminal fermentation remain uncertain. This study compared the effect of 20:5n-3 (eicosapentaenoic acid; EPA), 22:5n-3 (docosapentaenoic acid; DPA), and 22:6n-3 (docosahexaenoic acid; DHA) on rumen fermentation and BH of C18 FA and was conducted simultaneously in cows and sheep to provide novel insights into interspecies differences. The trial was performed in vitro using batch cultures of rumen microorganisms with inocula collected from cannulated cows and ewes. The PUFA were added at a dose of 2% incubated dry matter, and treatment effects on ruminal C18 FA concentrations, PUFA disappearances, and fermentation parameters (gas production, ammonia and volatile FA concentrations, and dry matter and neutral detergent fiber disappearances) were examined after 24 h of incubation. A principal component analysis suggested that responses to PUFA treatments explained most of the variability; those of ruminant species were of lower relevance. Overall, EPA and DHA were equally effective for inhibiting the saturation of trans-11 18:1 to 18:0 and had a similar influence on ruminal fermentation in cows and sheep (e.g., reductions in gas production and acetate:propionate ratio). Nevertheless, DHA further promoted alternative BH pathways that lead to trans-10 18:1 accumulation, and EPA seemed to have specific effects on 18:3n-3 metabolism. Only minor variations attributable to DPA were observed in the studied parameters, suggesting a low contribution of this FA to the action of marine lipids. Although most changes due to the added PUFA were comparable in bovine and ovine, there were also relevant specificities, such as a stronger inhibition of 18:0 formation in cows and a greater increase in 18:3n-3 metabolites in sheep. No direct relationship between in vitro disappearance of the incubated PUFA and effect on BH (in particular, inhibition of the last step) was found in either cows or ewes, calling into question a putative link between extent of disappearance and toxicity for microbiota. Conversely, an association between the influence of these PUFA on ruminal lipid metabolism and fermentation may exist in both species. In vivo verification of these findings would be advisable.

Rumen Fluid Metabolomics Analysis Associated with Feed Efficiency on Crossbred Steers

The rumen has a central role in the efficiency of digestion in ruminants. To identify potential differences in rumen function that lead to differences in average daily gain (ADG), rumen fluid metabolomic analysis by LC-MS and multivariate/univariate statistical analysis were used to identify differences in rumen metabolites. Individual feed intake and body-weight was measured on 144 steers during 105 d on a high concentrate ration. Eight steers with the greatest ADG and 8 steers with the least-ADG with dry matter intake near the population average were selected. Blood and rumen fluid was collected from the 16 steers 26 d before slaughter and at slaughter, respectively. As a result of the metabolomics analysis of rumen fluid, 33 metabolites differed between the ADG groups based on t-test, fold changes and partial least square discriminant analysis. These metabolites were primarily involved in linoleic and alpha-linolenic metabolism (impact-value 1.0 and 0.75, respectively; P < 0.05); both pathways were down-regulated in the greatest-ADG compared with least-ADG group. Ruminal biohydrogenation might be associated with the overall animal production. The fatty acids were quantified in rumen and plasma using targeted MS to validate and evaluate the simple combination of metabolites that effectively predict ADG.

The Structural and Functional Capacity of Ruminal and Cecal Microbiota in Growing Cattle Was Unaffected by Dietary Supplementation of Linseed Oil and Nitrate

Microorganisms in the digestive tract of ruminants differ in their functionality and ability to use feed constituents. While cecal microbiota play an important role in post-rumen fermentation of residual substrates undigested in the rumen, limited knowledge exists regarding its structure and function. In this trial we investigated the effect of dietary supplementation with linseed oil and nitrate on methane emissions and on the structure of ruminal and cecal microbiota of growing bulls. Animals were allocated to either a CTL (control) or LINNIT (CTL supplemented with 1.9% linseed and 1.0% nitrates) diet. Methane emissions were measured using the GreenFeed system. Microbial diversity was assessed using amplicon sequencing of microbial genomic DNA. Additionally, total RNA was extracted from ruminal contents and functional mcrA and mtt genes were targeted in amplicon sequencing approach to explore the diversity of functional gene expression in methanogens. LINNIT had no effect on methane yield (g/kg DMI) even though it decreased methane production by 9% (g/day; P < 0.05). Methanobrevibacter- and Methanomassiliicoccaceae-related OTUs were more abundant in cecum (72 and 24%) compared to rumen (60 and 11%) irrespective of the diet (P < 0.05). Feeding LINNIT reduced the relative abundance of Methanomassiliicoccaceae mcrA cDNA reads in the rumen. Principal component analysis revealed significant differences in taxonomic composition and abundance of bacterial communities between rumen and cecum. Treatment decreased the relative abundance of a few Ruminococcaceae genera, without affecting global bacterial community structure. Our research confirms a high level of heterogeneity in species composition of microbial consortia in the main gastrointestinal compartments where feed is fermented in ruminants. There was a parallel between the lack of effect of LINNIT on ruminal and cecal microbial community structure and functions on one side and methane emission changes on the other. These results suggest that the sequencing strategy used here to study microbial diversity and function accurately reflected the absence of effect on methane phenotypes in bulls treated with linseed plus nitrate.

Protein profile and physicochemical characteristics of meat of lambs fed diets supplemented with rapeseed oil, fish oil, carnosic acid, and different chemical forms of selenium

Abstract. The objective of this study was to evaluate the physicochemical characteristics of the longissimus muscle of lambs fed a control diet containing 3 % rapeseed oil (RO) (group I); an experimental diet with 2 % RO and 1 % fish oil (FO) (group II); or experimental diets with coupled addition of 2 % RO, 1 % FO, and 0.1 % carnosic acid (CA) (group III) without/with 0.35 ppm Se as selenized yeast (SeY) (group IV) or selenate (SeVI as sodium selenate, Na2SeO4) (group V). The results showed that dietary FO or SeVI affected the ultimate pH and meat color in comparison to lambs fed the control diet. The differences noted between diets in the case of muscle tissue were as follows: myosin HC (heavy chain) and LC1 (light chain), 150 kDa, α-actinin, 60 kDa, and TnT (troponin T), 30 kDa protein. The addition of FO to lamb diets resulted in a lower content of 30 kDa proteins, which are indicators of proteolysis. Considering the protein profile of drip loss, results showed effects of dietary administration of FO, CA, and Se (as SeY and SeVI) on the abundance of the following sarcoplasmic proteins: AMPDA (AMP deaminase), PGM (phosphoglucomutase), PK/PGI (pyruvate kinase/phosphoglucose isomerase), CK/PGAK (creatine kinase/phosphoglycerate kinase), ALD (aldolase), LDH (lactate dehydrogenase), PGAM (phosphoglycerate mutase), and TPI (triosephosphate isomerase). The lower content of TPI (in group II with comparison to groups III–V) and PGAM (in group II with comparison to group I and III) could be due to a higher ultimate pH in the group with FO addition, whereas lower contents of CK/PGAK, ALD, and LDH were attributed to Se addition. In comparison to the control diet, all experimental diets without SeVI decreased the content of the sum of all assayed amino acids ( ∑ AAs), indispensable amino acids ( ∑ IAAs), and dispensable amino acids ( ∑ DAAs) in the muscle. The highest ratios of  ∑ IAAs to  ∑ DAAs and  ∑ IAAs to  ∑ AAs were found in the muscle of lambs fed the diet containing RO, FO, and CA. The FO-supplemented diet with CA and SeVI increased the abundance of methionine in the muscle in comparison to the control diet and the FO-supplemented diet without/with CA.

Diurnal Dynamics of Gaseous and Dissolved Metabolites and Microbiota Composition in the Bovine Rumen

Diurnal patterns of ruminal fermentation metabolites and microbial communities are not commonly assessed when investigating variation in ruminal CH4 production. The aims of this study were to monitor diurnal patterns of: (i) gaseous and dissolved metabolite concentrations in the bovine rumen, (ii) H2 and CH4 emitted, and (iii) the rumen microbiota. Furthermore, the effect of dietary inclusion of linseed oil on these patterns was assessed. Four rumen cannulated multiparous cows were used in a cross-over design with two 17 days periods and two dietary treatments: a control diet and a linseed oil supplemented diet [40% maize silage, 30% grass silage, 30% concentrate on dry matter (DM) basis for both diets; fat contents of 33 vs. 56 g/kg of DM]. On day 11, rumen contents were sampled for 10 h after morning feeding to profile gaseous and dissolved metabolite concentrations and microbiota composition. H2 and CH4 emission (mass per unit of time) was measured in respiration chambers from day 13 to 17. A 100-fold increase in ruminal H2 partial pressure (contribution to the total pressure of rumen headspace gases) was observed at 0.5 h after feeding. This peak was followed by a decline to basal level. Qualitatively similar patterns after feeding were also observed for H2 and CH4 emission, ethanol and lactate concentrations, and propionate molar proportion, although the opposite pattern was seen for acetate molar proportion. Associated with these patterns, a temporal biphasic change in the microbial composition was observed as based on 16S ribosomal RNA with certain taxa specifically associated with each phase. Bacterial concentrations (log10 16S ribosomal RNA gene copies based) were affected by time, and were increased by linseed oil supplementation. Archaeal concentrations (log10 16S ribosomal RNA gene copies based) tended to be affected by time and were not affected by diet, despite linseed oil supplementation decreasing CH4 emission, tending to decrease the partial pressure of CH4, and tending to increase propionate molar proportion. Linseed oil supplementation affected microbiota composition, and was most associated with an uncultivated Bacteroidales taxon. In summary, our findings support the importance of diurnal dynamics for the understanding of VFA, H2, and CH4 production.

Dietary n-6:n-3 Fatty Acid Ratios Alter Rumen Fermentation Parameters and Microbial Populations in Goats

Revealing the ruminal fermentation patterns and microbial populations as affected by dietary n-6:n-3 PUFA ratio would be useful for further clarifying the role of the rumen in the lipid metabolism of ruminants. The objective of the present study was to investigate the effects of dietary n-6:n-3 PUFA ratios on fermentation characteristics, fatty acid (FA) profiles, and microbial populations in the rumen of goats. A total of twenty-one goats were randomly assigned to three dietary treatments with different n-6:n-3 PUFA ratios of 2.27:1 (low ratio, LR), 5.01:1 (medium ratio, MR), and 10.38:1 (high ratio, HR). After 100 days of feeding, all goats were slaughtered. Dietary n-6:n-3 PUFA ratios had no effect (P > 0.05) on rumen pH and NH₃N concentration. Goats fed HR diet had lower (P < 0.05) propionate and total volatile fatty acids and higher (P < 0.05) butyrate compared with those fed the MR and LR diets. The proportion of C18:0 decreased (P < 0.05) as dietary n-6:n-3 PUFA ratios increased. The proportions of C18:1 trans-11, C18:2n-6, cis-9 trans-11 CLA, and C20:4n-6 were greater in the HR goats compared with the MR and LR goats. Lowering dietary n-6:n-3 PUFA ratios enhanced (P < 0.05) the proportion of C18:3n-3 and total n-3 PUFA in the rumen fluid of goats. The populations of R. albus and R. flavefaciens decreased (P < 0.05) as the n-6:n-3 PUFA ratios increased in diet. Diet had no effect (P > 0.05) on the ruminal populations of F. succinogenes, total bacteria, methanogens, total protozoa, Entiodinium, and Holotrich. The population of B. fibrisolvens was lower (P < 0.05) in the LR goats compared with the MR and HR goats. It was concluded that HR would increase the concentration of cis-9 trans-11 CLA and C18:1 trans-11 in the rumen. However, LR whould decrease the B. fibrisolvens population, which is involved in the BH process in the rumen. Further research is needed to evaluate the potential role and contribution of rumen microbiome in the metabolism of FA in the rumen.

The effects of adding fat to diets of lactating dairy cows on total-tract neutral detergent fiber digestibility: A meta-analysis

The objective of this meta-analysis was to determine the effects of supplemental fat on fiber digestibility in lactating dairy cattle. Published papers that evaluated the effects of adding fat to the diets of lactating dairy cattle on total-tract neutral detergent fiber digestibility (ttNDFd) and dry matter intake (DMI) were compiled. The final data set included 108 fat-supplemented treatment means, not including low-fat controls, from 38 publications. The fat-supplemented treatment means exhibited a wide range of ttNDFd (49.4% ± 9.3, mean ± standard deviation) and DMI (21.3 kg/d ± 3.5). Observations were summarized as the difference between the treatment means for fat-supplemented diets minus their respective low-fat control means. Additionally, those differences were divided by the difference in diet fatty acid (FA) concentration between the treatment and control diets. Treatment means were categorized by the type of fat supplement. Supplementing 3% FA in the diet as medium-chain fats (containing predominately 12- and 14-carbon saturated FA) or unsaturated vegetable oil decreased ttNDFd by 8.0 and 1.2 percentage units, respectively. Adding 3% calcium salts of long-chain FA or saturated fats increased ttNDFd by 3.2 and 1.3 percentage units, respectively. No other fat supplement type affected ttNDFd. Except for saturated fats and animal-vegetable fats, supplementing dietary fat decreased DMI. When the values for changes in ttNDFd are regressed on changes in DMI there was a positive relationship, though the coefficient of determination is only 0.20. When changes in ttNDFd were regressed on changes in DMI, within individual fat supplement types, there was no relationship within calcium salt supplements. There was a positive relationship between changes in ttNDFd and changes in DMI for saturated fats. Neither relationship suggested that the increased ttNDFd with calcium salts or saturated FA was due to decreased DMI for these fat sources. A subset of the means included measured ruminal neutral detergent fiber digestion. Analysis of this smaller data set did not suggest that ruminal neutral detergent fiber digestibility is depressed by fat supplementation more than ttNDFd. Adding fats, other than those with medium-chain FA, consistently increased digestible energy density of the diet. However, due to reduced DMI, this increased energy density may not result in increased digestible nutrient intake.

Protection of sunflower seed and sunflower meal protein with malic acid and heat: effects on in vitro ruminal fermentation and methane production

BACKGROUND

Combined malic acid-heat treatments of protein supplements have been shown to reduce ruminal protein degradation, but there is no information on their possible influence on ruminal fermentation and methane emissions. This study aimed to investigate the effects of the treatment of sunflower meal (SM) and sunflower seed (SS) with malic acid and subsequent drying at 150°C for 1 (MAL1) or 3 h (MAL3) on in vitro rumen fermentation and methane emission using ruminal fluid from sheep as inoculum.

RESULTS

Compared with untreated samples, the MAL3 treatment reduced (P < 0.05) the dry matter effective degradability (DMED) by 78% and 46% for SS and SM, respectively, indicating heat damage. The MAL1 treatment reduced the DMED of SS by 22%, but did not affect (P > 0.05) total volatile fatty acid production for any feed. This treatment also increased (P < 0.05) the propionate proportion (by 17.7% and 15.6% for SS and SM, respectively) and decreased (P < 0.05) methane production (by 15.5% and 11.3%, respectively) and ammonia-N concentrations (by 26.5% and 14.5%, respectively).

CONCLUSION

The MAL1 treatment was effective in reducing both ammonia-N concentrations and methane emissions without depressing SS and SM fermentation, but more research is needed to formulate environmentally cleaner diets for ruminants. © 2016 Society of Chemical Industry.

Modulation of in vitro rumen biohydrogenation by Cistus ladanifer tannins compared with other tannin sources

BACKGROUND

Tannins are polyphenolic compounds able to modify the ruminal biohydrogenation (BH) of unsaturated fatty acids, but their activity may vary among different tannin sources. The effect of rockrose (Cistus ladanifer) on BH has never been compared with other more common tannin sources. Tannin extracts (100 g kg^-1 substrate dry matter) from chestnut (CH), quebracho (QB), grape seed (GS) and rockrose (CL) were incubated in vitro for 6 h with ruminal fluid using as substrate a feed containing 60 g kg^-1 of sunflower oil. A control treatment with no added tannins was also included.

RESULTS

Compared with the control, GS and CL, but not CH and QB, increased (P < 0.05) the disappearance of c9,c12-18:2 with a consequent larger production of c9,t11-18:2 and t11-18:1. However, no differences among treatments (P > 0.05) were observed for the disappearance of c9-18:1 and c9,c12,c15-18:3. The production of 18:0 was not different (P > 0.05) among treatments, although its proportion in the total BH products was lower (P < 0.05) for GS than for the other treatments.

CONCLUSION

Condensed tannins from GS and, to a lesser extent, from CL stimulate the first steps of BH, without a clear inhibition of 18:0 production. © 2016 Society of Chemical Industry.

Effect of incremental amounts of camelina oil on milk fatty acid composition in lactating cows fed diets based on a mixture of grass and red clover silage and concentrates containing camelina expeller

Camelina is an ancient oilseed crop that produces an oil rich in cis-9,cis-12 18:2 (linoleic acid, LA) and cis-9,cis-12,cis-15 18:3 (α-linolenic acid, ALA); however, reports on the use of camelina oil (CO) for ruminants are limited. The present study investigated the effects of incremental CO supplementation on animal performance, milk fatty acid (FA) composition, and milk sensory quality. Eight Finnish Ayrshire cows (91d in milk) were used in replicated 4×4 Latin squares with 21-d periods. Treatments comprised 4 concentrates (12kg/d on an air-dry basis) based on cereals and camelina expeller containing 0 (control), 2, 4, or 6% CO on an air-dry basis. Cows were offered a mixture of grass and red clover silage (RCS; 1:1 on a dry matter basis) ad libitum. Incremental CO supplementation linearly decreased silage and total dry matter intake, and linearly increased LA, ALA, and total FA intake. Treatments had no effect on whole-tract apparent organic matter or fiber digestibility and did not have a major influence on rumen fermentation. Supplements of CO quadratically decreased daily milk and lactose yields and linearly decreased milk protein yield and milk taste panel score from 4.2 to 3.6 [on a scale of 1 (poor) to 5 (excellent)], without altering milk fat yield. Inclusion of CO linearly decreased the proportions of saturated FA synthesized de novo (4:0 to 16:0), without altering milk fat 18:0, cis-9 18:1, LA, and ALA concentrations. Milk fat 18:0 was low (<5g/100g of FA) across all treatments. Increases in CO linearly decreased the proportions of total saturates from 58 to 45g/100g of FA and linearly enriched trans-11 18:1, cis-9,trans-11 18:2, and trans-11,cis-15 18:2 from 5.2, 2.6, and 1.7 to 11, 4.3, and 5.8g/100g of FA, respectively. Furthermore, CO quadratically decreased milk fat trans-10 18:1 and linearly decreased trans-10,cis-12 18:2 concentration. Overall, milk FA composition on all treatments suggested that one or more components in camelina seeds may inhibit the complete reduction of 18-carbon unsaturates in the rumen. In conclusion, CO decreased the secretion of saturated FA in milk and increased those of the trans-11 biohydrogenation pathway or their desaturation products. Despite increasing the intake of 18-carbon unsaturated FA, CO had no effect on the secretions of 18:0, cis-9 18:1, LA, or ALA in milk. Concentrates containing camelina expeller and 2% CO could be used for the commercial production of low-saturated milk from grass- and RCS-based diets without major adverse effects on animal performance.