Biohydrogenation of 22:6n-3 by Butyrivibrio proteoclasticus P18

Background: Rumen microbes metabolize 22:6n-3. However, pathways of 22:6n-3 biohydrogenation and ruminal microbes involved in this process are not known. In this study, we examine the ability of the well-known rumen biohydrogenating bacteria, Butyrivibrio fibrisolvens D1 and Butyrivibrio proteoclasticus P18, to hydrogenate 22:6n-3. Results: Butyrivibrio fibrisolvens D1 failed to hydrogenate 22:6n-3 (0.5 to 32 mu g/mL) in growth medium containing autoclaved ruminal fluid that either had or had not been centrifuged. Growth of B. fibrisolvens was delayed at the higher 22:6n-3 concentrations; however, total volatile fatty acid production was not affected. Butyrivibrio proteoclasticus P18 hydrogenated 22:6n-3 in growth medium containing autoclaved ruminal fluid that either had or had not been centrifuged. Biohydrogenation only started when volatile fatty acid production or growth of B. proteoclasticus P18 had been initiated, which might suggest that growth or metabolic activity is a prerequisite for the metabolism of 22:6n-3. The amount of 22:6n-3 hydrogenated was quantitatively recovered in several intermediate products eluting on the gas chromatogram between 22:6n-3 and 22:0. Formation of neither 22:0 nor 22:6 conjugated fatty acids was observed during 22:6n-3 metabolism. Extensive metabolism was observed at lower initial concentrations of 22:6n-3 (5, 10 and 20 mu g/mL) whereas increasing concentrations of 22:6n-3 (40 and 80 mu g/mL) inhibited its metabolism. Stearic acid formation (18:0) from 18:2n-6 by B. proteoclasticus P18 was retarded, but not completely inhibited, in the presence of 22:6n-3 and this effect was dependent on 22:6n-3 concentration. Conclusions: For the first time, our study identified ruminal bacteria with the ability to hydrogenate 22:6n-3. The gradual appearance of intermediates indicates that biohydrogenation of 22:6n-3 by B. proteoclasticus P18 occurs by pathways of isomerization and hydrogenation resulting in a variety of unsaturated 22 carbon fatty acids. During the simultaneous presence of 18:2n-6 and 22:6n-3, B. proteoclasticus P18 initiated 22:6n-3 metabolism before converting 18:1 isomers into 18:0

Dietary fish oil supplements depress milk fat yield and alter milk fatty acid composition in lactating cows fed grass silage-based diets

201

Grass Silage: Factors Affecting Efficiency of N Utilisation in Milk Production

Key points Low efficiency of N utilisation for milk production in cows fed grass silage-based diets is mainly due to excessive N losses in the rumen. The type and extent of in silo fermentation can alter the balance of absorbed nutrients. There is very little experimental evidence that the capture of N in the rumen can be improved by a better synchrony between energy and N release in the rumen. Nitrogen losses in the rumen can be reduced by decreasing the ratio between rumen degradable N and fermentable energy. Rapeseed meal has increased milk protein output more than isonitrogenous soybean meal supplementation, probably due to higher concentration of histidine in rapeseed protein. Efficiency of N utilisation for milk production is not necessarily lower for the grass silage based diets compared to other diets

Effects of oil and natural or synthetic vitamin E on ruminal and milk fatty acid profiles in cows receiving a high-starch diet

Among trans fatty acids, trans-10,cis-12 CLA has negative effects on cow milk fat production and can affect human health. In high-yielding dairy cows, a shift from the trans-11 to the trans-10 pathway of biohydrogenation (BH) can occur in the rumen of cows receiving high-concentrate diets, especially when the diet is supplemented with unsaturated fat sources. In some but not all experiments, vitamin E has been shown to control this shift. To ascertain the effects of vitamin E on this shift of BH pathway, 2 studies were conducted. The first study explored in vitro the effects of addition of natural (RRR-α-tocopherol acetate) and synthetic (dl-α-tocopherol acetate) vitamin E. Compared with control and synthetic vitamin E, the natural form resulted in a greater trans-10/trans-11 ratio; however, the effect was very low, suggesting that vitamin E was neither a limiting factor for rumen BH nor a modulator of the BH pathway. An in vivo study investigated the effect of natural vitamin E (RRR-α-tocopherol) on this shift and subsequent milk fat depression. Six rumenfistulated lactating Holstein cows were assigned to a 2 × 2 crossover design. Cows received 20-kg DM of a control diet based on corn silage with 22% of wheat, and after 2 wk of adaptation, the diet was supplemented with 600 g of sunflower oil for 2 more weeks. During the last week of this 4-wk experimental period, cows were divided into 2 groups: an unsupplemented control group and a group receiving 11 g of RRR-α-tocopherol acetate per day. A trans-10 shift of ruminal BH associated with milk fat depression due to oil supplementation of a high-wheat diet was observed, but vitamin E supplementation of dairy cows did not result in a reversal toward a trans-11 BH pathway, and did not restore milk fat content

Dietary forage to concentrate ratio and sunflower oil supplement alter rumen fermentation, ruminal methane emissions, and nutrient utilization in lactating cows

ISSN-numero puuttuu.201

Correspondence

quantification, real-time PCR, rumen, stearic acid producers

Maidontuotannon ympäristövaikutusten rajoittaminen eläingenetiikan ja ravitsemuksen työkaluja kehittämällä

MAKERA -hankkeen loppuraportti, hankkeen dnro 2667/312/2009

Renal and mammary PD excretion in Holstein/Friesian dairy cows: Its potential as a non-invasive index of protein metabolism

The significance and contribution of rumen synthesised MCP (MCP) in the context of current metabolisable protein (MP) systems and variations in the energetic efficiency of MCP synthesis reported in the literature are reviewed. The estimation of MCP supply from urinary PD (PD) excretion is discussed and reviewed in detail, with the conclusion that it is a reliable non-invasive technique. HPLC methodologies were developed to determine PD, pseudouridine and creatinine in bovine urine and allantoin in bovine milk. A series of experiments were conducted to evaluate the potential of the PD technique using spot urine samples or measurements of allantoin in milk as on-farm diagnostics of MCP supply. Prediction of daily mean urinary molar ratios of PDs to creatinine (PD/c) ratios from spot urine samples was poor due to diurnal variations, the extent of which was influenced by feeding regimen. Furthermore, prediction of urinary PD excretion from daily mean PD/c ratios was poor due to between-cow variations in urinary creatinine excretion. On this basis the spot urine sampling technique was considered unreliable and a total urine collection proved necessary. Variabilty of urinary creatinine excretion precludes its use as a urinary output marker for individual cows. Urinary pseudouridine excretion was independent of nutrient supply but appeared to be influenced by metabolic changes occurring during lactation. In two experiments, dietary fermentable metabolisable energy (FME) supply was manipulated during early and late lactation. For both experiments, individual cow urinary PD excretion was poorly predicted from calculated FME intake or MCP supply. Based on mean treatment values, urinary PD excretion was accurately predicted from calculated MCP. Individual cow milk allantoin excretion or concentration were poorly correlated with urinary PD excretion, calculated FME intake or MCP. Relationships derived using mean treatment values indicated that milk allantoin excretion or concentration were strongly correlated with urinary PD excretion or calculated MCP. Variability precludes the use of milk allantoin as an index of MCP supply for individual cows, but it appears as reliable as urinary PD excretion when used on a herd or group feeding basis