Estimation of the stoichiometry of volatile fatty acid production in the rumen of lactating cows

The purpose of this study was to improve the prediction of the quantity and type of Volatile Fatty Acids (VFA) produced from fermented substrate in the rumen of lactating cows. A model was formulated that describes the conversion of substrate (soluble carbohydrates, starch, hemi-cellulose, cellulose, and protein) into VFA (acetate, propionate, butyrate, and other VFA). Inputs to the model were observed rates of true rumen digestion of substrates, whereas outputs were observed molar proportions of VFA in rumen fluid. A literature survey generated data of 182 diets (96 roughage and 86 concentrate diets). Coefficient values that define the conversion of a specific substrate into VFA were estimated meta-analytically by regression of the model against observed VFA molar proportions using non-linear regression techniques. Coefficient estimates significantly differed for acetate and propionate production in particular, between different types of substrate and between roughage and concentrate diets. Deviations of fitted from observed VFA molar proportions could be attributed to random error for 100%. In addition to regression against observed data, simulation studies were performed to investigate the potential of the estimation method. Fitted coefficient estimates from simulated data sets appeared accurate, as well as fitted rates of VFA production, although the model accounted for only a small fraction (maximally 45%) of the variation in VFA molar proportions. The simulation results showed that the latter result was merely a consequence of the statistical analysis chosen and should not be interpreted as an indication of inaccuracy of coefficient estimates. Deviations between fitted and observed values corresponded to those obtained in simulations. (c) 2005 Elsevier Ltd. All rights reserved.

Effects of volatile fatty acid supply on their absorption and on water kinetics in the rumen of sheep sustained by intragastric infusions

Three sheep fitted with a ruminal cannula and an abomasal catheter were used to study water kinetics and absorption of VFA infused continuously into the rumen. The effects of changing VFA concentrations in the rumen by shifting VFA infusion rates were investigated in an experiment with a 3 x 3 Latin square design. On experimental days, the animals received the basal infusion rate of VFA (271 mmol/h) during the first 2 h. Each animal then received VFA at a different rate (135, 394, or 511 mmol/h) for the next 7.5 h. Using soluble markers (polyethylene glycol and Cr-EDTA), ruminal volume, liquid outflow, apparent water absorption, and VFA absorption rates were estimated. There were no significant effects of VFA infusion rate on ruminal volume and water kinetics. As the VFA infusion rate was increased, VFA concentration and osmolality in the rumen were increased and pH was decreased. There was a biphasic response of liquid outflow to changes in the total VFA concentration in the rumen, as both variables increased together up to a total VFA concentration of 80.1 mM, whereas, beyond that concentration, liquid outflow remained stable at an average rate of 407 mL/h. There were significant linear (P = 0.003) and quadratic (P = 0.001) effects of VFA infusion rate on the VFA absorption rate, confirming that VFA absorption in the rumen is mainly a concentration-dependent process. The proportion of total VFA supplied that was absorbed in the rumen was 0.845 (0.822, 0.877, and 0.910 for acetate, propionate, and butyrate, respectively). The molar proportions of acetate, propionate, and butyrate absorbed were affected by the level of VFA infusion in the rumen, indicating that this level affected to a different extent the absorption of the different acids.

Impact of variation in structure of condensed tannins from sainfoin (Onobrychis viciifolia) on in vitro ruminal methan production and fermentation characteristics

Our study investigated the effects of condensed tannins (CT) on rumen in vitro methane (CH4) production and fermentation characteristics by incubating lucerne in buffered rumen fluid in combination with different CT extracts at 0 (control), 40, 80 and 120 g CT/kg of substrate DM. Condensed tannins were extracted from four sainfoin accessions: Rees ‘A’, CPI63763, Cotswold Common and CPI63767. Gas production (GP) was measured using a fully automated GP apparatus with CH4 measured at distinct time points. Condensed tannins differed substantially in terms of polymer size and varied from 13 (Rees ‘A’) to 73 (CPI63767) mean degree of polymerization, but had relatively similar characteristics in terms of CT content, procyanidin: prodelphinidin (PC: PD) and cis:trans ratios. Compared to control, addition of CT from CPI63767 and CPI63763 at 80 and 120 g CT/kg of substrate DM reduced CH4 by 43% and 65%, and by 23% and 57%, respectively, after 24-h incubation. Similarly, CT from Rees ‘A’ and Cotswold Common reduced CH4 by 26% and 46%, and by 28% and 46% respectively. Addition of increasing level of CT linearly reduced the maximum rates of GP and CH4 production, and the estimated in vitro organic matter digestibility. There was a negative linear and quadratic (p < 0.01) relation between CT concentration and total volatile fatty acid (VFA) production. Inclusion of 80 and 120 g CT/kg of substrate DM reduced (p < 0.001) branched-chain VFA production and acetate: propionate ratio and was lowest for CPI63767. A decrease in proteolytic activity as indirectly shown by a change in VFA composition favouring a shift towards propionate and reduction in branched-chain VFA production varied with type of CT and was highest for CPI63767. In conclusion, these results suggest that tannin polymer size is an important factor affecting in vitro CH4 production which may be linked to the CT interaction with dietary substrate or microbial cells.

Dietary manipulation of fatty acid composition in lamb meat and its effect on the volatile aroma compounds of grilled lamb

The effect on lamb muscle of five dietary supplements high in polyunsaturated fatty acids (PUFA) was measured. The supplements were linseed oil, fish oil, protected lipid (high in linoleic acid (C18:2 n-6) and alpha-linolenic acid (C18:3 n-3)), fish oil/marine algae (1:1), and protected lipid/marine algae (1:1). Eicosapentaenoic acid (C20:5 n-3) and docosahexaenoic acid (C22:6 n-3) were found in the highest amounts in the meat from lambs fed diets containing algae. Meat from lambs fed protected lipid had the highest levels of C18:2 n-6 and C18:3 n-3, due to the effectiveness of the protection system. In grilled meat from these animals, volatile compounds derived from n-3 fatty acids were highest in the meat from the lambs fed the fish oil/algae diet, whereas compounds derived from n-6 fatty acids were highest in the meat from the lambs fed the protected lipid diet. (C) 2004 Elsevier Ltd. All rights reserved.

A comparison of the aroma volatiles and fatty acid compositions of grilled beef muscle from Aberdeen Angus and Holstein-Friesian steers fed diets based on silage or concentrates

This paper compares the volatile compound and fatty acid compositions of grilled beef from Aberdeen Angus and Holstein-Friesian steers slaughtered at 14 months, each breed fed from 6 months on either cereal-based concentrates or grass silage. Linoleic acid levels were higher in the muscle of concentrates-fed animals, which in the cooked meat resulted in increased levels of several compounds formed from linoleic acid decomposition. Levels of alpha-linolenic acid, and hence some volatile compounds derived from this fatty acid, were higher in the meat from the silage-fed steers. 1-Octen-3-ol, hexanal, 2-pentylfuran, trimethylamine, cis- and trans-2-octene and 4,5-dimethyl-2-pentyl-3-oxazoline were over 3 times higher in the steaks from the concentrates-fed steers, while grass-derived 1-phytene was present at much higher levels in the beef from the silage-fed steers. Only slight effects of breed were observed. (C) 2004 Elsevier Ltd. All rights reserved.

Effect of linseed oil and fish oil alone or as an equal mixture of ruminal fatty acid metabolism in growing steers fed maize silage-based diets

Based on the potential benefits to human health there is interest in increasing 18:3n-3, 20:5n-3, 22:6n-6, and cis-9,trans-11 conjugated linoleic acid (CLA) in ruminant foods. Four Aberdeen Angus steers (406 ± 8.2 kg BW) fitted with rumen and duodenal cannulae were used in a 4 x 4 Latin square experiment with 21 d periods to examine the potential of fish oil (FO) and linseed oil (LO) in the diet to increase ruminal outflow of trans-11 18:1 and total n-3 polyunsaturated fatty acids (PUFA) in growing cattle. Treatments consisted of a control diet (60:40; forage:concentrate ratio, on a DM basis, respectively) based on maize silage, or the same basal ration containing 30 g/kg DM of FO, LO or a mixture (1:1, w/w) of FO and LO (LFO). Diets were offered as total mixed rations and fed at a rate of 85 g DM/kg BW0.75/d. Oils had no effect (P = 0.52) on DM intake. Linseed oil had no effect (P > 0.05) on ruminal pH or VFA concentrations, while FO shifted rumen fermentation towards propionate at the expense of acetate. Compared with the control, LO increased (P < 0.05) 18:0, cis 18:1 (Δ9, 12-15), trans 18:1 (Δ4-9, 11-16), trans 18:2, geometric isomers of ∆9,11, ∆11,13, and ∆13,15 CLA, trans-8,cis-10 CLA, trans-10,trans-12 CLA, trans-12,trans-14 CLA, and 18:3n-3 flow at the duodenum. Inclusion of FO in the diet resulted in higher (P < 0.05) flows of cis-9 16:1, trans 16:1 (Δ6-13), cis 18:1 (Δ9, 11, and 13), trans 18:1 (Δ6-15), trans 18:2, 20:5n-3, 22:5n-3, and 22:6n-3, and lowered (P < 0.001) 18:0 at the duodenum relative to the control. For most fatty acids at the duodenum responses to LFO were intermediate of FO and LO. However, LFO resulted in higher (P = 0.04) flows of total trans 18:1 than LO and increased (P < 0.01) trans-6 16:1 and trans-12 18:1 at the duodenum compared with FO or LO. Biohydrogenation of cis-9 18:1 and 18:2n-6 in the rumen was independent of treatment, but both FO and LO increased (P < 0.001) the extent of 18:3n-3 biohydrogenation compared with the control. Ruminal 18:3n-3 biohydrogenation was higher (P < 0.001) for LO and LFO than FO, while biohydrogenation of 20:5n-3 and 22:6n-3 in the rumen was marginally lower (P = 0.05) for LFO than FO. In conclusion, LO and FO at 30 g/kg DM altered the biohydrogenation of unsaturated fatty acids in the rumen causing an increase in the flow of specific intermediates at the duodenum, but the potential of these oils fed alone or as a mixture to increase n-3 PUFA at the duodenum in cattle appears limited.

Effect of replacing calcium salts of palm oil distillate with rapeseed oil, milled or whole rapeseeds on milk fatty-acid composition in cows fed maize silage-based diets

Inclusion of rapeseed feeds in dairy cow diets has the potential to reduce milk fat saturated fatty acid (SFA) and increase cis-monounsaturated fatty acid (cis-MUFA) content but effectiveness may depend on the form in which the rapeseed is presented. Four mid-lactation Holstein dairy cows were allocated to four maize silage-based dietary treatments according to a 4 x 4 Latin Square design, with 28-day experimental periods. Treatments consisted of a control diet (C containing 49 g/kg dry matter (DM) of calcium salts of palm oil distillate (CPO), or 49 g/kg DM of oil supplied as whole rapeseeds (WR), rapeseeds milled with wheat (MR) or rapeseed oil (RO). Replacing CPO with rapeseed feeds had no effect (P > 0.05) on milk fat and protein content, while milk yields were higher (P < 0.05) for RO and MR compared with WR (37.1, 38.1 and 34.3 kg/day, respectively). Substituting CPO with RO or MR reduced (P < 0.05) milk fat total SFA content (69.6, 55.6, 71.7 and 61.5 g/100g fatty acids for C, RO, WR and MR, respectively) and enhanced (P < 0.05) milk cis-9 18:1 MUFA concentrations (corresponding values 18.6, 24.3, 17.0 and 23.0 g/100g fatty acids) compared with C and WR. Treatments RO and MR also increased (P < 0.05) milk trans-MUFA content (4.4, 6.8, 10.5 g/100g fatty acids, C MR and RO, respectively). A lack of significant changes in milk fat composition when replacing CPO with WR suggests limited bioavailability of fatty acids in intact rapeseeds. In conclusion, replacing a commercial palm oil-based fat supplement in the diet with milled rapeseeds or rapeseed oil represented an effective strategy to alter milk fatty acid composition with the potential to improve human health. Inclusion of processed rapeseeds offered a good compromise for reducing milk SFA and increasing cis-MUFA, whilst minimising milk trans-MUFA and negative effects on animal performance.

Effects of dietary vitamin A concentration of roasted soybean inclusion on marbling, adipose cellularity, and fatty acid composition of beef

A feedlot trial was conducted to determine the effect of dietary vitamin A concentration and roasted soybean (SB) inclusion on carcass characteristics, adipose tissue cellularity, and muscle fatty acid composition. Angus-crossbred steers (n = 168; 295 +/- 1.8 kg) were allotted to 24 pens (7 steers each). Four treatments, in a 2 x 2 factorial arrangement, were investigated: no supplemental vitamin A, no roasted soybeans (NANS); no vitamin A, roasted SB (20% of the diet on a DM basis; NASB); with supplemental (2,700 IU/kg) vitamin A, no roasted SB (WANS); and with supplemental vitamin A, roasted SB (WASB). Diets included high moisture corn, 5% corn silage, 10 to 20% supplement, and 20% roasted SB in the SB treatments on a DM basis. The calculated vitamin A concentration in the basal diet was < 1,300 IU/kg of DM. Blood samples (2 steers/pen) were collected for serum vitamin A determination. Steers were slaughtered after 168 d on feed. Carcass characteristics and LM composition were determined. Fatty acid composition of LM was analyzed, and adipose cellularity in the i.m. and s.c. depots was determined. No vitamin A x SB interactions were detected (P > 0.10) for cattle performance, carcass composition, or muscle fatty acid composition. Low vitamin A diets (NA) did not affect (P > 0.05) ADG, DMI, or G:F. Quality grade tended (P = 0.07) to be greater in NA steers. Marbling scores and the percentage of carcasses grading > or = Choice(-) were 10% greater for NA steers, although these trends were not significant (P = 0.11 and 0.13, respectively). Backfat thickness and yield grade were not affected (P > 0.26) by vitamin A supplementation. Composition of the LM was not affected (P > 0.15) by vitamin A or SB supplementation. Serum retinol at slaughter was 44% lower (P < 0.01) for steers fed NA than for steers supplemented with vitamin A (23.0 vs. 41.1 microg/dL). A vitamin A x SB interaction occurred (P < 0.05) for adipose cellularity in the i.m. depot; when no SB was fed, vitamin A supplementation decreased cell density and increased cell size. However, when SB was fed, vitamin A supplementation did not affect adipose cellularity. Adipose cellularity at the s.c. depot was not affected (P > 0.18) by vitamin A or SB treatments. Fatty acid profile of the LM was not affected by vitamin A (P > 0.05), but SB increased (P < 0.05) PUFA (7.88 vs. 4.30 g/100 g). It was concluded that feeding NA tended to increase marbling without affecting back-fat and yield grade. It appeared that NA induced hyperplasia in the i.m. but not in the s.c. fat depot.

Effect of replacing calcium salts of palm oil distillate with extruded linseeds on milk fatty acid composition in Jersey and Holstein cows

Clinical and biomedical studies have provided evidence for the critical role of n-3 fatty acids on the reduction of chronic disease risk in humans, including cardiovascular disease. In the current experiment, the potential to enhance milk n-3 content in two breeds with inherent genetic differences in mammary lipogenesis and de novo fatty acid synthesis was examined using extruded linseeds. Six lactating cows (three Holstein and three Jersey) were used in a two-treatment switchback design with 3 × 21-day experimental periods to evaluate the effect of iso-energetic replacement of calcium salts of palm oil distillate (CPO) in the diet (34 g/kg dry matter (DM)) with 100 g/kg DM extruded linseeds (LIN). For both breeds, replacing CPO with LIN had no effect (P > 0.05) on DM intake or milk yield, but reduced (P < 0.05) milk fat and protein yield (on average, from 760 to 706 and 573 to 552 g/day, respectively). Relative to CPO, the LIN treatment reduced (P < 0.01) total saturated fatty acid content and enhanced (P < 0.001) 18:3n-3 in milk, whereas breed by diet interactions were significant for milk fat 16:0, total trans fatty acid and conjugated linoleic acid concentrations. Increases in 18:3n-3 intake derived from LIN in the diet were transferred into milk with a mean marginal transfer efficiency of 1.8%. Proportionate changes in milk fatty acid composition were greater in the Jersey, highlighting the importance of diet–genotype interactions on mammary lipogenesis. More extensive studies are required to determine the role of genotype on milk fat composition responses to oilseeds in the diet.

Effect of replacing grass silage with maize silage in the diet on bovine milk fatty acid composition

Even though extensive research has examined the role of nutrition on milk fat composition, there is less information on the impact of forages on milk fatty acid (FA) composition. In the current study, the effect of replacing grass silage (GS) with maize silage (MS) as part of a total mixed ration on animal performance and milk FA composition was examined using eight multiparous mid-lactation cows in a replicated 4 X 4 Latin square with 28-day experimental periods. Four treatments comprised the stepwise replacement of GS with MS (0, 160, 334 and 500 g/kg dry matter (DM)) in diets containing a 54:46 forage: concentrate ratio on a DM basis. Replacing GS with MS increased (P < 0.001) the DM intake, milk yield and milk protein content. Incremental replacement of GS with MS in the diet enhanced linearly (P < 0.001) the proportions of 6:0-14:0, decreased (P < 0.01) the 16:0 concentrations, but had no effect on the total milk fat saturated fatty acid content. Inclusion of MS altered the distribution of trans-18:1 isomers and enhanced (P < 0.05) total trans monounsaturated fatty acid and total conjugated linoleic acid content. Milk total n-3 polyunsaturated fatty acid (PUFA) content decreased with higher amounts of MS in the diet and n-6 PUFA concentration increased, leading to an elevated n-6: n-3 PUFA ratio. Despite some beneficial changes associated with the replacement of GS with MS, the overall effects on milk FA composition would not be expected to substantially improve long-term human health. However the role of forages on milk fat composition must also be balanced against the increases in total milk and protein yield on diets containing higher proportions of MS.

Effects of forage source and soybean and marine algal oil supplementation on milk fatty acid composition in ewes

The objective of the present studies was to determine effects of basal dietary forage source on the response of milk fatty acid composition to an oil supplement based (2:1, respectively, w/w) on soybean oil and marine algae biomass oil high in cis-9, cis-12 C18:2n − 3 and C22:6n − 3, respectively. In Study 1, Hampshire × Dorset ewes (48) were randomly assigned to one of four treatments and 12 pens in a completely randomized design blocked on the basis of lambing date and number of lambs suckled. Control rations (60:40 forage:concentrate, dry matter (DM) basis) based on alfalfa pellets (AP) or corn silage (CS) were fed from lambing. Beginning at 22 days postpartum, three pens of ewes fed AP and three pens of ewes fed CS were supplemented with oil (30 g/kg of ration DM) in place of corn meal. Average ewe DM intake (DMI) and average daily gain (ADG) were measured weekly. Milk yield and composition were measured at 42 days postpartum. DMI was lower (P<0.02) for CS and for oil, but milk yield was not affected by forage source or oil supplementation. Milk fat content was higher for oil (P<0.10) and milk protein content was higher for AP (P<0.04). Total CLA concentration (g/100 g fatty acids) increased (P<0.01) with CS and oil, and the response to oil was greater for AP (P<0.04). Similarly, total trans-C18:1 and C22:6ω−3 concentrations were higher for CS and oil, but the response to oil was greater for CS (P<0.06 and P<0.01, respectively). In Study 2, the experiment was repeated using alfalfa haylage (AH) instead of AP. The DMI decreased (P<0.05) with oil feeding, but was not affected by forage source. Milk yield was decreased by feeding oil with AH, but not by feeding oil with CS (P<0.03). Milk fat content tended to be increased by feeding oil with AH, but tended to be decreased by feeding oil with CS (P<0.08). Total CLA concentration was increased (P<0.01) for AH versus CS and by oil, and the response to oil supplementation was greater for AH (P<0.01). In contrast, total trans-C18:1 concentration was higher for CS versus AH, with a greater response to oil for CS (P<0.05). Feeding marine oil increased the C22:6ω−3 (P<0.01) concentration, and the response was greater for AH (P<0.04). To further characterize the response of milk fat composition to dietary oil in ewes, a third study used six pens of three ewes each assigned to either the control CS diet used for Study 2 or the same diet supplemented with 45 g/kg (DM basis) of the oil mixture. Feeding oil had no effect on DMI, milk yield or milk fat concentration, but again increased (P<0.001) total trans-C18:1 and C22:6ω−3 concentrations and numerically increased (114%) total CLA concentration. Milk fatty acid composition responses to supplemental vegetable and marine oils were affected by forage source. Milk trans-C18:1 concentration was higher when CS was fed in Studies 1 and 2, but the effect of forage species on CLA concentration differed between studies, which may reflect differences in diet PUFA content and consumption, as well as amounts of dietary starch and fiber consumed. Despite large increases in trans-C18:1 concentration, milk fat content was not decreased by feeding unsaturated oils to ewes, even at diet levels of 45 g/kg of ration DM.