Odd- And Branched-chain Fatty Acids Research Articles

Short communication: Effects of diets containing supplemental fats on ruminal fermentation and milk odd- and branched-chain fatty acids in dairy cows

There is a growing interest in odd- and branched-chain fatty acids (OBCFA) in milk following reports that several branched-chain fatty acids (FA) have health promoting effects, and certain milk OBCFA could serve as a biomarker to assess ruminal function. Twenty-four Holstein cows were fed 3 low-forage diets containing 30 g/kg of dry matter of prilled palm fat (PPF), sunflower oil (SO), or an equal mixture of both fats (experiment 1) or 3 diets containing 30 g/kg of dry matter of SO with a forage-to-concentrate ratio of 39:61, 44:56, or 48:52 (Experiment 2); diets were fed to investigate milk OBCFA composition and to explore the relationships between ruminal VFA and milk OBCFA using principal component analysis. Including SO in diets decreased yields of milk 13:0 anteiso, 15:0 anteiso, 15:0, 17:0, cis-9 15:1, and cis-9 17:1 compared with PPF. The molar proportion of ruminal propionate was the lowest and the yields of milk 14:0 iso and 16:0 iso were the greatest with the diet containing both fat supplements. Replacing concentrate with forages linearly increased ruminal acetate and yields of milk 13:0 iso, 14:0 iso, 15:0 iso, 16:0 iso, 17:0 iso, 13:0 anteiso, 15:0 anteiso, 15:0, 17:0, cis-9 15:1, and cis-9 17:1. The principal component analysis revealed that ruminal molar proportion of acetate related to concentrations of milk iso FA containing <17-carbon, whereas ruminal propionate related to milk 15:0, 17:0, cis-9 15:1, and cis-9 17:1, with the stronger correlations between milk OBCFA and ruminal acetate than propionate. No associations were found between ruminal molar proportion of butyrate and milk OBCFA concentrations. The results suggest that complete replacement of PPF with SO at 30 g/kg of dry matter in low-forage diets is not an effective strategy to enhance bioactive branched-chain FA in milk, rather this feeding practice lowers anteiso FA in milk; however, increasing forage proportion in diets containing SO enhances several iso and anteiso FA in milk. The milk OBCFA concentrations have stronger correlations with ruminal acetate molar proportion than with propionate or butyrate in cows fed diets containing supplemental fats.

Fatty acid and lipid contents differentiation in cuts of rabbit meat

ABSTRACTThe study aimed at quantifying fatty acids (FA), especially the health-promoting ones, in cuts of rabbit meat. Loin, containing mostly glycolytic muscles, had less lipids than cuts containing oxidative (hind leg) or intermediate muscles (foreleg and brisket). Brisket had the highest polyunsaturated FA (PUFA), odd- and branched-chain FAs (OBCFA) and palmitoleic acid C16:1 n-7 contents, better n-6/n-3 proportion, advantageous nutritional indexes (AI, TI, H/H) than other cuts. Hind leg contained less atherogenic saturated FAs (LCSFA) than other cuts. Foreleg was rich in two important n-3 LC-PUFAs: C20:5 and C22:5. The results suggest that apart from the preferred cuts (loin and hind leg) used in gastronomy, brisket and foreleg should be included for being rich in nutritionally valuable PUFA, especially from the n-3 family. Daily portion (250 g) of foreleg would cover 16% of the requirement for EPA and DHA, and the same amount of brisket or hind leg—11%.

The relationship between odd- and branched-chain fatty acids and microbial nucleic acid bases in rumen.

ObjectiveThis study aims to identify the relationship between odd- and branched-chain fatty acids (OBCFAs) and microbial nucleic acid bases in the rumen, and to establish a model to accurately predict microbial protein flow by using OBCFA.MethodsTo develop the regression equations, data on the rumen contents of individual cows were obtained from 2 feeding experiments. In the first experiment, 3 rumen-fistulated dry dairy cows arranged in a 3×3 Latin square were fed diets of differing forage to concentration ratios (F:C). The second experiment consisted of 9 lactating Holstein dairy cows of similar body weights at the same stage of pregnancy. For each lactation stage, 3 cows with similar milk production were selected. The rumen contents were sampled at 4 time points of every two hours after morning feeding 6 h, and then to analyse the concentrations of OBCFA and microbial nucleic acid bases in the rumen samples.ResultsThe ruminal bacteria nucleic acid bases were significantly influenced by feeding diets of differing forge to concentration ratios and lactation stages of dairy cows (p<0.05). The concentrations of OBCFAs, especially odd-chain fatty acids and C15:0 isomers, strongly correlated with the microbial nucleic acid bases in the rumen (p<0.05). The equations of ruminal microbial nucleic acid bases established by ruminal OBCFAs contents showed a good predictive capacity, as indicated by reasonably low standard errors and high R-squared values.ConclusionThis finding suggests that the rumen OBCFA composition could be used as an internal marker of rumen microbial matter.

Optimization of milk odd and branched-chain fatty acids analysis by gas chromatography using an extremely polar stationary phase

Odd and branched-chain fatty acids (OBCFA) are of interest, since they have bioactive properties and could be regarded biomarkers of ruminant fat intake. An accurate analysis of the individual OBCFA in milk by gas chromatography (GC) is not easy due to milk fat complexity. The availability of ionic liquid stationary phases as SLB-IL111 can be a useful tool to discriminate OBCFA from other milk FA eluting in the same chromatographic regions. The elution behavior of OBCFA on SLB-IL111 was evaluated based on different GC oven temperature programs. All programs assayed discriminated 11:0, iso 13:0, anteiso 13:0, iso 15:0, anteiso 15:0, 15:0 and iso 17:0. Using an initial temperature of 150°C for 1h, 13:0 and iso 16:0 were separated from trans-12:1 and 13-14:1, respectively, whereas iso 18:0 was discriminated from cis-16:1 isomers. 17:0 and 21:0 were well resolved only when an initial GC temperature of 160°C was applied.

Milk fat secretion in Holstein dairy cows: Insights from grain type and oil supplement

Effects of grain type and dietary oil supplement on milk fat depression and milk fatty acid (FA) composition of dairy cows were evaluated using eight multiparous Holstein cows (77±22.1 days in milk; mean±SD) in a replicated 4×4 Latin square design with a 2×2 factorial arrangement of diets. Experimental diets contained either ground barley or ground corn supplemented with either fish oil or soybean oil at 2% of dietary dry matter (DM). Experimental periods were 25 d, with the final 7 d used for sample and data collection. Dry matter intake tended (P=0.09) to be greater for barley- vs. corn-based diets (23.2 vs. 22.3kg/d), but was reduced for the fish oil compared to soybean oil supplemented diets (21.1 vs. 24.3kg/d; P<0.001). Total FA intake was greater in corn-based diets and also in soybean oil supplemented diets. Regardless of type of the diet fed, MFD occurred. Although milk fat yield was not affected, the barley-based diets increased (P<0.001) the concentration of mixed-origin FA (C16:0 plus cis-9 C16:1) but decreased the concentration of preformed FA (P<0.001) as compared with corn-based diets. Corn-based diets increased concentration of both trans-11 C18:1 (P=0.03) and cis-9, trans-11 C18:2 (P=0.01) which was a reflection of greater intake of cis-9, cis-12 C18:2 as substrate for rumen biohydrogenation. Severity of MFD was greater for fish oil than for soybean oil which was evidenced by the increased concentration and yield of biohydrogenation intermediates (especially trans-10 C18:1) associated with MFD (r =–0.61; n =32) in milk fat. However, fish oil increased concentration of both trans-11 C18:1 (P=0.001) and cis-9, trans-11 C18:2 (P<0.001) as compared with soybean oil. Grain type and oil supplement did not interact to affect milk odd- and branched-chain FA (OBCFA) concentration. Cows fed barley-based diets (P<0.001) and soybean oil supplemented diets (P<0.001) produced greater OBCFA in milk fat. Overall, there was no interaction between the type of grain and oil supplement on induction of MFD and milk fat yield. However, milk fatty acid composition was differently modified by the grain type and an increase in the concentration of mixed-origin FA of fish oil supplemented diets was unable to attenuate the severity of MFD because of the concomitant decrease in concentrations of de novo synthesized- and preformed-FA as compared with soybean oil supplemented diets.

Odd- and branched-chain fatty acids in goat milk as indicators of the diet composition

This work aimed to determine if the milk fat contents of odd- and branched-chain fatty acids (OBCFA) could be linked to the diet composition in goats, by canonical discriminant analysis (CDA). The OBCFA contents of 32 milk fat samples from two feeding trials (two treatments per trial) were used. In both experiments, the goats were fed a diet, with the same forage/concentrate ratio and nutritive value, which was supplemented or not with 30 g/d of linseed oil. The starch/non-forage NDF ratio of the diet was 3.1 in the first experiment and was lowered to 0.8 in the second experiment by replacing part of the cereals in the concentrate with soybean hulls. Milk fat composition analyses were grouped into four classes in the CDA. Stepwise backward selection identified C13:0 iso, C14:0 iso, C17:0 anteiso, C18:0 iso and C17:0 + cis-9 C17:1 as valid predictors. The first two discriminant functions (DF) explained 82.2 and 13.9% of total variance. DF1 and DF2 differentiated milk samples by the non-forage NDF content and linseed oil supplementation of the diet, respectively. C14:0 iso and C17:0 anteiso were indicative of the diets with high non-forage NDF and starch contents, respectively. C17:0 + cis-9 C17:1 and both C18:0 iso and C13:0 iso contributed to identify the diets with and without added linseed oil, respectively. In conclusion, CDA allowed to identify which milk OBCFA were the best indicators of the starch/non-forage NDF ratio and the presence of linseed oil in the diets fed to dairy goats.

Comparison of Fatty Acid Composition of Milk from Simmental and Polish Holstein-Friesian Cows in Different Production Seasons

Abstract The aim of this study was to determine the fatty acid (FA) profile of Simmental cow milk in relation to lipid intake in feeds and their composition, and to compare it with FA composition of milk from cows of Polish Holstein-Friesian (PHF) breed. To this end, 104 milk samples were collected from Simmental cows and 52 milk samples derived from PHF breed were taken over a 2-year period. The season significantly influenced both contents of lipid, dry matter and crude protein as well as FA content in lipids extracted from forages. Winter and autumn seasons were characterized by a significantly higher intake of lipids with forages resulting from the intake of fresh silages, compared with the other seasons when the animals were fed stored silages. This was reflected in the highest content of conjugated linoleic acid (CLA) c-9 t-11 C18:2 in milk from the autumn season. Compared with PHF, milk from Simmentals had a higher content of short-chain saturated FAs (SCSFAs) and was characterized by great differences in FA contents determined in the group of odd- and branched-chain FAs (OBCFAs). Milk from Simmental cows had the butyric acid C4:0 and iso C15:0 content of 4.99 and 1.20 g/100 g FA on average, respectively, which have been associated with benefits for human health.

Influence of the calf presence during milking on dairy performance, milk fatty acid composition, lipolysis and cheese composition in Salers cows during winter and grazing seasons.

The milking of Salers cows requires the presence of the calf. The removal of the calf would simplify the milking routine, but it could also modify the milk yield and the milk and cheese composition. Therefore, the aim of this experiment was to evaluate the effect of calf presence during milking during sampling period (winter or grazing periods), on dairy performance, milk fatty acid (FA) composition, lipolysis and cheese yield and composition. Nine and 8 Salers lactating cows were milked in the presence (CP) or absence (CA) of their calves respectively. During winter, the cows were fed a hay-based diet and then they only grazed a grassland pasture. Calf presence during milking increased milk yield and milk 16:0 concentration and decreased milk fat content and milk total odd- and branched-chain FA (OBCFA) concentrations. Calf presence only increased initial lipolysis in milk collected during the winter season. Milk from CP cows compared to CA cows resulted in a lower cheese yield and ripened cheeses with lower fat content. Milk from the grazing season had lower saturated medium-chain FA and OBCFA concentrations and higher 18:0, cis-9-18:1, trans-11-18:1 and cis-9, trans-11-CLA concentrations than that from the winter season. Initial milk lipolysis was higher in the winter than in the grazing season. These variations could be due to seasonal changes in the basal diet. Furthermore, the effect of calf presence during milking on milk fat composition was lower than that on dairy performance, cheese yield and composition. Removing the calf during the milking of Salers cows seems feasible without a decrease in milked milk, and with a positive effect on cheese yield and fat content, under the condition that we are able to select cows having the capacity to be milked easily without the calf.

Effect of lipid supplementation on milk odd- and branched-chain fatty acids in dairy cows

Eight ruminally fistulated, multiparous Holstein cows were arranged in a double 4×4 Latin square with 14-d periods to investigate the effects of lipid supplementation on performance, rumen parameters, the milk odd- and branched-chain fatty acid (OBCFA) profile, and the relationships between milk OBCFA and rumen parameters. Lipid supplementation is known to inhibit microbial growth in the rumen, decrease de novo microbial fatty acid synthesis, and increase the uptake of circulating fatty acids by the mammary gland; treatments were selected to isolate these effects on the milk OBCFA profile. The 4 treatments were (1) a lipid-free emulsion medium infused in the rumen (CTL), (2) soybean oil as a source of polyunsaturated fatty acids infused in the rumen (RSO), (3) saturated fatty acids (38% 16:0, 40% 18:0) infused in the rumen (RSF), and (4) saturated fatty acids infused in the abomasum (ASF). Fat supplements were provided continuously as emulsions at a rate of 450g/d. Preplanned contrasts compared CTL to RSO, RSO to RSF, and RSF to ASF. Infusing RSO slightly decreased ruminal pH, but did not affect volatile fatty acids profile and milk fat concentration as compared with CTL. The yields of energy-corrected milk, fat, and protein were greater with RSF compared with RSO. The concentration of odd-chain fatty acids was decreased by RSO, whereas even-chain iso fatty acids were not affected. Milk fat concentration of 17:0 + cis-9 17:1 was higher for RSF than for RSO, due to the saturated fatty acids supplement containing 2% 17:0 + cis-9 17:1. Limited differences were observed in the milk OBCFA profile between RSF and ASF. A multiple regression analysis yielded the following equation for predicting rumen pH based on milk fatty acids: pH=6.24 – (0.56×4:0) + (1.67 × iso 14:0) + (4.22 × iso 15:0) + (9.41×22:0). Rumen propionate concentration was negatively correlated with milk fat concentration of iso 14:0 and positively correlated with milk 15:0, whereas the acetate-to-propionate ratio gave the opposite correlations with milk iso 14:0 and 15:0. Milk fat concentration of 17:0 + cis-9 17:1 was not related to rumen propionate or to acetate-to-propionate ratio, due to the presence of 17:0 and cis-9 17:1 in the saturated fatty acids supplement. The results suggest that although lipid supplementation can affect the profile of milk OBCFA, the promise remains of using these milk fatty acids to evaluate rumen function.

Content and Composition of Branched-Chain Fatty Acids in Bovine Milk Are Affected by Lactation Stage and Breed of Dairy Cow.

Dairy products contain bioactive fatty acids (FA) and are a unique dietary source of an emerging class of bioactive FA, branched-chain fatty acids (BCFA). The objective of this study was to compare the content and profile of bioactive FA in milk, with emphasis on BCFA, among Holstein (HO), Jersey (JE), and first generation HO x JE crossbreeds (CB) across a lactation to better understand the impact of these factors on FA of interest to human health. Twenty-two primiparous cows (n = 7 HO, n = 7 CB, n = 8 JE) were followed across a lactation. All cows were fed a consistent total mixed ration (TMR) at a 70:30 forage to concentrate ratio. Time points were defined as 5 days in milk (DIM), 95 DIM, 185 DIM, and 275 DIM. HO and CB had a higher content of n-3 FA at 5 DIM than JE and a lower n-6:n-3 ratio. Time point had an effect on the n-6:n-3 ratio, with the lowest value observed at 5 DIM and the highest at 185 DIM. The content of vaccenic acid was highest at 5 DIM, yet rumenic acid was unaffected by time point or breed. Total odd and BCFA (OBCFA) were higher in JE than HO and CB at 185 and 275 DIM. Breed affected the content of individual BCFA. The content of iso-14:0 and iso-16:0 in milk was higher in JE than HO and CB from 95 to 275 DIM. Total OBCFA were affected by time point, with the highest content in milk at 275 DIM. In conclusion, HO and CB exhibited a higher content of several bioactive FA in milk than JE. Across a lactation the greatest content of bioactive FA in milk occurred at 5 DIM and OBCFA were highest at 275 DIM.

Relationship between milk odd and branched-chain fatty acids and urinary purine derivatives in dairy cows supplemented with quebracho tannins—A study to test milk fatty acids as predictors of rumen microbial protein synthesis

The purpose of this study was to explore the potential of milk odd and branched-chain fatty acids (OBCFA) as biomarkers for rumen microbial protein synthesis in dairy cows, and to study the effects of diets supplemented with different levels of quebracho tannin extract (QTE) on milk OBCFA.The experiment included 50 lactating German Holstein dairy cows divided into two groups of 25 animals each and lasted for six consecutive periods of 21 days (13 days of adaptation and 8 days of feed, milk, and urine sampling). The basal diet was a total mixed ration with a constant forage to concentrate ratio of 65:35 (Control, without QTE). A commercial QTE product was added to the basal diet at 15g and 30g/kg dry matter to create diets QTE15 and QTE30, respectively. Milk fat samples were analysed for OBCFA contents and urine for purine derivatives (PD), nitrogen (N), and creatinine concentrations.The QTE addition increased the concentrations of creatinine and the ratio between total PD and N in urine, whereas the concentrations of allantoin, total PD, and N in urine decreased with QTE addition. Similarly, addition of QTE decreased the proportions (g/100g fat) and yields (g/d) of milk OBCFA, with the exception of anteiso-C15:0 and anteiso-C17:0.Multivariate models to predict concentrations and ratios of PD, N, and creatinine in urine from milk OBCFA explained between 10% and 40% of the variance in the dataset of each predicted parameter. However, the explanation of that variance attributed to milk OBCFA was only between 2% and 26%. For most parameters, models developed from milk OBCFA proportions explained more variance in the dataset than those developed from OBCFA yields. Our findings suggest that milk OBCFA are poor indicators of rumen microbial protein synthesis in dairy cows.

Postruminal synthesis modifies the odd- and branched-chain fatty acid profile from the duodenum to milk

Milk odd- and branched-chain fatty acids (OBCFA) have been suggested as potential biomarkers for rumen function. The potential of milk OBCFA as a biomarker depends on whether their profile reflects the profile observed in the duodenum. The objective of this study was to evaluate whether the OBCFA profile in duodenum samples is reflected in plasma and milk. For this, 2 dairy cattle experiments were used. In experiment 1, 4 Holstein cows fitted with rumen and proximal duodenum cannulas were used in a 4×4 Latin square design. The treatments consisted of 2 nitrogen levels (143 vs. 110g of crude protein/kg of dry matter for high and low N, respectively) combined with either 1 of the 2 energy sources (i.e., starch from barley, corn, and wheat or fiber from soybean hulls and dehydrated beet pulp). In experiment 2, 4 Holstein cows fitted with rumen and proximal duodenum cannulas were used in a 3×3 Latin square design, with the treatments consisting of 3 diets: (1) RNB−, a diet with a crude protein content of 122g/kg of dry matter, predicted to provide protein digested in the small intestine according to the requirement of the animals, but with a shortage of rumen degradable protein; (2) RNB− to which 6g/d of niacin was added through inclusion in the mineral and vitamin premix, and (3) RNB− to which urea was added to balance rumen degradable N supply resulting in a CP content of 156g/kg of dry matter. In both experiments, samples of duodenal digesta, plasma, and milk were collected and analyzed for fatty acids. Additionally, lipids in plasma samples were separated in lipid classes and analyzed for fatty acids. The OBCFA profile in milk was enriched in 15:0, iso-17:0, anteiso-17:0, and cis-9–17:1 as compared with duodenal samples, and milk secretions even exceeded duodenal flows, which suggests occurrence of postruminal synthesis, such as de novo synthesis, desaturation, and elongation. The postruminal modification of the OBCFA profile might hamper the application of OBCFA as diagnostic tools of rumen function.

Effects of grape seed supplementation, alone or associated with linseed, on ruminal metabolism in Sarda dairy sheep

Grape seed is a by-product of the winery and distillery industry which could be used in animal nutrition. To test the hypothesis that dietary supplementation with this by-product can decrease the biohydrogenation (BH) of healthy fatty acids (FA), the present study evaluated the effects of grape seed supplementation, alone or combined with linseed, on ruminal BH processes in dairy sheep. In this 60-d trial, 24 lactating Sarda dairy ewes were assigned to four homogeneous groups and fed as follows: (1) control diet (CON), (2) a diet supplemented with 300g/d per head of grape seed (GS), (3) a diet supplemented with 220g/d per head of extruded linseed (LIN), (4) and a diet supplemented with a mix of both grape seed and linseed (300 and 220g/d per head, respectively) (MIX). Ammonia, pH, volatile fatty acids (VFA) and FA composition were determined in rumen liquor at three sampling dates (20, 40 and 60 d). Rumen pH was not influenced by diet (P>0.05). The ammonia content was increased (P<0.05) in GS and MIX compared with LIN and CON. The molar proportions of acetate and propionate and their ratio were not affected by the diet (P>0.05), whereas the molar proportion of butyrate was the lowest in MIX. Rumenic acid (RA; CLA cis-9,trans-11) concentration increased in GS compared with CON (0.78 vs. 0.45mg/100mg FA; P<0.05), whereas the percentage of vaccenic acid (VA; C18:1 trans-11) tended to increase (P<0.10) in GS compared with CON. The concentration of VA was higher in MIX than in CON (8.18 vs. 3.77mg/100mg FA; P<0.05), whereas RA did not differ between the same groups. The concentration of linoleic acid (LA; C18:2 n–6) decreased and stearic acid (SA; C18:0) increased in all supplemented groups, whereas linolenic acid (LNA; C18:3 n–3) decreased in the two groups receiving grape seed compared with CON and LIN. The concentration of total odd- and branched-chain fatty acids (OBCFA) decreased in all supplemented groups compared with CON (P<0.05), evidencing that grape seed and linseed supplementation influenced the ruminal BH processes. Grape seed was able to increase the accumulation of RA when supplemented alone, and of VA when combined with linseed; however, the rumen accumulation of SA in both groups supplemented with grape seed evidenced that this by-product was not effective in decreasing the BH of dietary polyunsaturated fatty acids (PUFA).

Technical note: Fatty acids and purine profile of cecum and colon bacteria as indicators of equine microbial metabolism1

The potential use of odd- and branched-chain fatty acids (OBCFA) and purine bases (PB) as microbial markers in the equine hindgut was studied. For this purpose, feed particles adherent bacteria [solid associated bacteria (SAB)] and planktonic bacteria [liquid associated bacteria (PAB)] were isolated from total cecum and colon contents of 8 healthy, crossbred horses (9 ± 3 yr). Horses were fasted for 12 to 15 h before slaughter, and the cecum and colon were identified and clamped in their extremities to avoid mixing of digesta contents. The total cecum or colon contents was collected into thermal containers previously filled with CO2, immediately transported to the laboratory, and subjected to separation of solid and liquid phases to obtain bacterial PAB and SAB pellets from each horse. Overall differences observed were mainly between site of bacterial collection (cecum vs. colon) rather than between type of bacterial population (PAB vs. SAB). Cecal bacteria fraction had greater (P < 0.05) OM, PB, and branched-chain fatty acids (BCFA):odd-chain fatty acids (OFA) ratio but less (P < 0.05) BCFA, OFA, BCFA:PB ratio, and adenine:guanine ratio than colon bacterial biomass. Results indicated that the composition of cecal and colon bacteria is very different from that of similar ecosystems (e.g., rumen). These differences can be a reflection of different growth stages or nutrition of particular populations as well as different bacterial metabolic activities. Results presented herein provide evidence that PB and fatty acids can be used as microbial markers in equine studies.

Effect of dietary proportion of grass silage on milk fat with emphasis on odd- and branched-chain fatty acids in dairy cows

High proportions of forage in diets fed to dairy cows are interesting options in conventional production, and mandatory in organic dairy farming (e.g., within the European Union). The objectives of the present study were to study the milk fatty acid (FA) profiles, with particular focus on the odd- and branched-chain FA (OBCFA) and their association with diet composition, using 3 different proportions of grass silage in the diet. The OBCFA profiles in milk have been suggested to be potential markers to assess nutrient supply to the cows. The study included data from 24 cows in 2008 and 26 cows in 2009, using pooled milk samples from morning and evening milking within 24h. The 3 diets were composed of the same feeds: grass silage and grain-based concentrate, but the silage component was fed in different proportions, namely 50, 70, and 85% of total dry matter intake. The cows were in late lactation, with a mean of 220 (SD=15) days in milk in 2008, and 216 (SD=35) days in milk in 2009, at the onset of the trial. Increased proportions of grass silage in the diet increased the intake of C18:3n-3, and decreased the intake of C18:2n-6 and intake of total FA. The daily intake of C18:3n-3 and C18:2n-6 was reflected in a similar increase in milk C18:3n-3, whereas the concentration of milk C18:2n-6 decreased with increasing proportion of grass silage in the diet. Increased proportions of grass silage in the diet increased the concentration of conjugated linoleic acid and the linear odd-chain FA C15:0 and C17:0, the branched-chain iso C15:0 and total OBCFA in milk. The concentration of total OBCFA in milk was shown to be positively correlated with dietary content of neutral detergent fiber. This suggests that the concentration of milk OBCFA may be useful in the future to indicate low forage intake in cows under conditions when it is not possible to measure individual forage intake.

Diurnal variation in fatty acid profiles in rumen digesta from dairy cows grazing high-quality pasture

Six dairy cows receiving a once-daily high-quality pasture allocation in the afternoon were used to investigate the relationship between diurnal variation in rumen fermentation activity and diurnal variation in rumen fatty acids (FA). Rumen digesta was collected every two hours over a 24h period, and rumen pH, volatile fatty acid (VFA) concentration and FA were measured. Cows receiving a once-daily pasture allocation in the afternoon had lower rumen pH at night than during the day, while the variation pattern of VFA concentration and rumen pH was exaggerated, but broadly similar, to previous reports of cows on once daily pasture allocation. Rumen FA profiles varied considerably over the grazing cycle, with the most dramatic changes occurred in the evening and overnight, especially for odd- and branched-chain fatty acids (OBCFA) and C18 FA. Diurnal variation in OBCFA clearly reflected the microbial colonization of the newly ingested pasture while the variation in C18 FA was consistent with known biohydrogenation reactions in the rumen. Disappearances of most C18:3 n-3 and C18:2 n-6 by 8–12h after ingestion suggests a rapid biohydrogenation of plant-derived polyunsaturated fatty acids (PUFA), while the high proportions of unsaturated C18 intermediates (especially C18:2 t11, c15 and C18:1 t11) and low proportion of C18:0 measured in the present study suggests inhibition of the final step of biohydrogenation by the high level of C18:3 n-3. The low proportion of conjugated linoleic acid (CLA c9, t11) in rumen digesta confirms an endogenous synthesis of this CLA isomer in milk fat of pasture based cows. The principal component analysis (PCA) biplot analysis provides a good description of variation in the overall FA, as well as the main biohydrogenation pathway for C18:3 n-3. The lower rumen buffering capacity (decreased rumen pH), dramatic decline in rumen microbial population (assessed by total OBCFA) observed between 18:00 and 20:00, as well as the large increase in plant-derived PUFA implied a reduced rumen biohydrogenation activity during the evening, which might provide an approach to reduce the biohydrogenation of protected PUFA supplements by strategic feeding to coincide with reduced rumen activity.

Rumen and milk odd- and branched-chain fatty acid proportions are minimally influenced by ruminal volatile fatty acid infusions

The objective of this study was to determine if ruminally infusing volatile fatty acid (VFA) increased concentration of their homologous odd- and branched-chain fatty acid (OBCFA) in rumen contents and milk. The influence of VFA on dry matter intake (DMI), blood metabolites, and blood insulin was also evaluated. Four mid-lactation cows were assigned to a 4×4 Latin square design with 48-h periods. Infusion treatments were acetate (AC), propionate (PR), isovalerate (IV), and anteisovalerate (AIV). Infusions began (time = 0) 5.5h before feeding at 17.4mmol of VFA/min and were terminated at 18h. Infusions rates were well above physiological levels for IV and AIV. Surprisingly, the greatest differences in rumen OBCFA were increases in rumen liquid iso C15:0 and nonbranched C17:0 for AIV. In addition, infusing AIV increased anteiso C15:0 and anteiso C17:0 in rumen solid contents. Infusing IV increased iso C15:0 in both rumen solids and milk. Propionate increased milk C15:0 and C17:0. Both gluconeogenic compounds, PR and AIV, had similar proportions of milk C15:0, which was greater than that obtained with AC and IV. Rumen and blood VFA were as expected, with increased concentrations of the VFA present in the infusate. At 23h, and consistently throughout infusions, DMI was similar for AC compared with PR and for AIV compared with IV. Both IV and AIV decreased DMI and energy balance; however, only IV increased plasma nonesterified fatty acids (121, 78, 172, and 102mM for AC, AIV, IV, and PR), increased β-hydroxybutyrate (10.8, 5.9, 51.9, 5.4mg/dL for AC, AIV, IV, and PR), and reduced plasma glucose (56.3, 59.1, 31.9, and 64.3mg/dL for AC, AIV, IV, and PR). Rumen and milk OBCFA responses were minimal following infusion of large amounts of IV and AIV, suggesting limited use of IV, and AIV for de novo OBCFA synthesis, either pre- or postabsorption. Minor increases in milk odd-chain fatty acids following large doses of ruminal PR support the presence of postabsorptive synthesis of these milk odd-chain fatty acids.

Milk odd- and branched-chain fatty acids as biomarkers of rumen function—An update

The main odd- and branched-chain fatty acids (OBCFA) in milk of dairy cows are isomers of tridecanoic acid (iso C13:0), tetradecanoic acid (iso C14:0), pentadecanoic acid (C15:0, iso C15:0 and anteiso C15:0), hexadecanoic acid (iso C16:0) and heptadecanoic acid (C17:0, iso C17:0 and anteiso C17:0). OBCFA are suggested to reflect rumen function (e.g. ruminal fermentation pattern, including methane, duodenal flow of microbial protein and acidosis). This relies on their predominant origin, i.e. bacteria leaving the rumen. The OBCFA are synthesized de novo by ruminal bacteria and incorporated in their cell membrane, suggesting a direct relation with bacterial biomass. Their potential as duodenal markers to quantify bacterial protein is strengthened by their constant relation with bacterial N content over a diversity of bacterial groups. From a limited database, evidence was shown of a useful relation of milk OBCFA yield with microbial protein flow from the rumen, but more research is needed to elucidate some discrepancies under diverse dietary regimes.Further, variation in the OBCFA profile of pure strains of ruminal bacteria were reported and are, in the current review, linked with their production of metabolites. From this, it can be assumed that the rumen fermentation pattern is related to the rumen OBCFA profile, which seems consistent for milk OBCFA. The close stoichiometric relation between ruminal VFA and methane further opens perspective for the use of OBCFA profiles in milk to quantify methane emissions. OBCFA consistently contributing to the predictive models, irrespective of the modeling approach are: iso C14:0 and iso C15:0, which positively relate to acetate and methane and negatively to propionate; and C15:0 and C17:0 which show an inverse relationship. Anteiso C15:0 seemed only relevant in the prediction of butyrate proportions.As changes in the ruminal microbial population (e.g. increased dominance of Streptococcus bovis) sometimes initiate a chain of events that eventually might lead to (sub-acute) ruminal acidosis, OBCFA in milk fat are targeted as candidates for the early detection of ruminal acidosis. Increasing C17:0+C17:1 cis-9 and decreasing iso C14:0 concentration show potential as indicators of sub-acute acidosis or were obvious before clinical symptoms of acute acidosis occurred. Collection of more experimental data is currently on-going for the development of more robust models to classify rumen health in continuous probability classes rather than discrete acidotic vs. non-acidotic cases.

Relationships between odd- and branched-chain fatty acid profiles in milk and calculated enteric methane proportion for lactating dairy cattle

The purpose of this study was to explore the relationships between odd- and branched-chain fatty acids (OBCFA) in milk with calculated enteric CH4 production for lactating dairy cows using multiple linear regression (MLR), partial least squares regression (PLS) and a genetic algorithm approach (GA). A dataset collected from 13 experiments containing 224 paired observations of measured acetate, propionate and butyrate proportions in rumen fluid VFA and 7 measured OBCFA was used. Methane proportion (mmol/mol VFA) was calculated from acetate, propionate and butyrate and expressed relative to the sum of these volatile fatty acids (VFA). Calculated CH4 production was related to milk OBCFA using MLR and PLS, resulting in a linear prediction model. The GA approach resulted in a model which predicted rumen VFA proportions of total VFA from milk OBCFA. Methane proportion was calculated from predicted acetate, propionate and butyrate proportions in total VFA based on rumen stoichiometry and compared with CH4 proportion calculated from measured VFA proportions. The prediction error was low (i.e., root mean square prediction error <5%), and models captured up to 66% of the variance in the data and the concordance correlation coefficient was close to 0.8. The variance of the prediction error was less than 40% of the variance of the calculated CH4 proportion. Seven milk OBCFA were initially considered as predictors, from which the branched-fatty acids iso C14:0, iso C15:0, iso C16:0 were positively related to calculated enteric CH4 production and the odd-fatty acids C15:0 and the sum of C17:0 and C17:1 cis–9 were negatively related to it. Relationships in this large data set identify the most relevant OBCFA in milk as potential predictors of rumen methanogenesis.This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.

Analysis of Milk Odd- and Branched-Chain Fatty Acids Using Fourier Transform (FT)-Raman Spectroscopy

Fourier transform (FT)-Raman spectra of pure C13:0, C15:0, C17:0, iso C14:0, iso C15:0, and ante C15:0 fatty acid methyl ester standards (FAMESs) and 75 milk fat samples from 6 different dietary experiments were acquired at room temperature (RT) and immediately after freezing at -80 °C (FT). The latter generally included much more well-defined and sharper scattering bands than those obtained at RT. Further, the spectra at FT revealed additional acuate bands in the vicinity of peculiar wavenumber regions, as well as an increase of Raman scattering intensity, which was sometimes associated with a shift of the peak. Partial least-squares (PLS) regression models based on either selected regions or the full spectra and using two pretreatment methods [multiplicative scatter correction (MSC, using raw spectra of milk fat only) and modified MSC (MMSC, a combination of pure FAMESs and milk fat spectra)] with cross-validation were used to evaluate the different types of milk fat FT-Raman spectra for the predictions of individual odd- and branched-chain fatty acids (OBCFAs) and their sums. In general, most individual (C15:0, ante C15:0, iso C17:0, and ante C17:0) and grouped (ODD, ANTE, and total OBCFAs) fatty acids were favorably (coefficient of determination, R(2) > 0.65) predicted using models with FT spectra only or a combination of RT and FT spectra (RFT), when compared to models with spectra analyzed at RT only. The results indicate the interest to use FT-Raman spectra collected at different temperatures for the prediction of narrow concentrations of saturated OBCFAs in milk fat.