Oats in the diet of dairy cows : milk production and enteric methane emissions

The overall aim of this thesis was to investigate whether replacing barley with oats as a grain supplement for dairy cows could reduce enteric methane (CH4) emissions without compromising milk production. Barley is a more common grain supplement in Sweden, mainly due to higher tabulated feeding values suggesting higher milk production with barley than with oats. In the first paper, different varieties of oats and barley were evaluated in vitro. Predicted in vivo CH4 emissions were lower from the oat diets than from the barley diets. In the second paper, barley was replaced by hulled oats as a grain supplement to dairy cows fed a grass silage-based diet. Replacing barley with oats decreased organic matter digestibility and metabolisable energy intake but did not affect milk or energy-corrected milk (ECM) yield. Daily CH4 emissions (g/d) and CH4 intensity (g/kg ECM) decreased by 4.7 and 4.8%, respectively. In the third paper, dairy cows were fed one of four grain supplements: barley, hulled oats, dehulled oats, or a mix of hulled and dehulled oats. Organic matter digestibility and metabolisable energy intake were similar between the barley diet and the oat diets, but milk and ECM yield were higher with the oat diets. Replacing hulled oats with dehulled oats did not affect milk or ECM yield. Daily CH4 emissions were similar between the barley diet and the oat diets. Yet, due to higher ECM yield, CH4 intensity was 5.7% lower with the oat diets. In the fourth paper, we investigated fatty acid composition of milk. Milk fat from cows fed oats contained lower concentrations of saturated fatty acids and higher concentrations of unsaturated fatty acids. In conclusion, replacing barley with oats in the diet of dairy cows does not compromise milk production and could offer a practical strategy to slightly reduce enteric CH4 emissions and to change milk quality to be more in line with dietary guidelines

Havre ger minskade utsläpp av metan från mjölkkor

I detta faktablad redovisas några av de resultat som framkommit i projektet ”Havre för en bättre miljö och mer hållbar mjölkproduktion”. Projektets syfte är att undersöka en realistisk strategi för att minska klimatavtrycket från mjölkproduktionen utan att produktiviteten påverkas negativt

Reducing methane production from stored feces of dairy cows by Asparagopsis taxiformis

The objective was to evaluate whether methane (CH4) production from stored feces of cows previously supplemented with Asparagopsis taxiformis (AT) in their diet was lower compared with the feces of cows not supplemented with AT. We also investigated the possibility of further reducing CH4 production by adding AT to the stored feces of cows. Fecal samples were provided from a feeding trial (during two different periods) of four cows divided into two different groups. One group was supplemented with AT at a level of 0.5% of the total organic matter intake, and the other group was not supplemented with AT. A 2 × 2 factorial design was set in the laboratory for the incubation of feces. Fecal samples from the two groups of cows were divided into two subsamples receiving either no addition of AT or the addition of AT at a level of 0.5% of OM incubated. This resulted in four treatments with two replicates per period. The same design was repeated during period two. In total, 400 g of fresh fecal samples were incubated in 1 L serum bottles for 9 weeks at 39°C in a water bath. CH4 and total gas production were measured on days 1, 4, and 7 and subsequently every 2nd week until the end of the incubation period. Enteric CH4 production showed a significant reduction (61%) when AT was supplemented in the diet of dairy cows. We found that CH4 production from the feces of dairy cows supplemented with AT in their diet was only numerically lower (P = 0.61). Adding AT to the feces of dairy cows significantly reduced CH4 production from the feces by 44% compared with feces without AT. There were no differences observed in the bacterial and archaeal community profiles of fecal samples between cows fed AT and those not fed AT. This study concludes that the addition of AT to stored feces can effectively reduce CH4 production from the feces of dairy cows

Relationship between predicted in vivo and observed in vivo methane production from dairy cows fed a grass-silage based diet with barley, oats, or dehulled oats as a concentrate supplement

The objectives of this study were to compare predicted in vivo methane (CH4) values based on data from an in vitro gas production experiment with observed in vivo values measured by the GreenFeed system, and to investigate the effect of the diet fed to donor animals of rumen inoculum (RI) on predicted in vivo CH4 production. For this purpose, we conducted an in vivo experiment simultaneously with an in vitro gas production experiment. The in vivo experiment (previously published) was a 4 × 4 Latin square design including 16 Nordic Red dairy cows. Cows were fed 60% grass silage and 40% concentrate which consisted of either barley, oats with hulls (hulled oats), dehulled oats, or a 50:50 mixture of hulled and dehulled oats on dry matter basis. The in vitro experiment was a 2 × 4 factorial design replicated in 4 runs. The in vitro diets were incubated for 48 h in two types of RI and formulated according to the diets fed in vivo. The RI was obtained from cows fed either barley (two cows) or hulled oats (two cows) as concentrate in the in vivo experiment. A set of models were applied to the gas and CH4 data obtained from the in vitro system to predict in vivo total gas and CH4 production. For the comparison between predicted in vivo and observed in vivo CH4, two different mean retention times (MRT of 35 and 50 h) in the rumen were used for the predictions. In the in vitro experiment, incubation residues were determined for organic matter digestibility and volatile fatty acids at 48 h of incubation. Assuming a MRT of 35 h in the rumen resulted in a significant relationship (P = 0.04) between predicted in vivo and observed in vivo CH4 yield (g/kg dry matter) with an R-square of 0.91 and a root mean square error of 0.20. Ranking of the diets in terms of their CH4 production was consistent between the in vitro and in vivo experiment. There were no significant interactions between diet and RI for any of the investigated parameters (P = 0.40). Rumen inoculum did not affect organic matter digestibility or total volatile fatty acid production. In conclusion, there was a good agreement between predicted in vivo and observed in vivo CH4 values. In addition, the diet of RI donor animal did not influence the comparison of diets in terms of CH4 production

Effect of replacing barley grain with oat grain in the diet of dairy cows on methane production in vitro

The aim of this master’s thesis was to investigate the potential of reducing enteric methane production from dairy cows by replacing barley grain with oat grain on a grass silage-based diet. The effects of grain species on in vitro methane production, digestibility, pH and volatile fatty acid (VFA) production pattern were investigated and a regression analysis was performed to entangle possible methane mitigating mechanisms of oats. The study was conducted in the laboratory at the Department of Agricultural Research for Northern Sweden in the autumn of 2016. An in vitro gas production system was applied, consisting of 16 diets with two replicates, four blanks and three runs, each with a three-day incubation time. The feed material consisted of eight varieties of barley, eight varieties of oats and timothy silage incubated at a grain/silage ratio of 1:1 on a dry matter basis. Rumen fluid was collected from two cannulated Nordic Red dairy cows after morning feeding. Gas sampling was performed at 2, 4, 8, 12, 24, 32 and 48 hours of incubation, meanwhile VFA-sampling, pH-measurements and sampling of incubation residues were performed at 48 hours. Methane production was estimated as predicted in vivo methane production and stoichiometrically predicted methane production. The in vitro digestibility was determined as true dry matter digestibility (TDMD). Content of indigestible neutral detergent fiber (iNDF) was determined by applying a 12-day in situ incubation in two Ayrshire dairy cows. Oats had a higher content of crude protein, neutral detergent fiber (NDF), iNDF and fat compared to barley, whereas barley had a higher content of starch. Replacing barley with oats decreased predicted in vivo methane production by 9% and stoichiometrically predicted methane production by 11%. Variety within grain was not found to have any significant effect on methane production. True DM digestibility and total VFA production were lower in oat-based diets compared to barley-based diets. No significant differences were observed between the diets considering VFA molar proportions. The pH was lower in barley-based diets compared to oat-based diets. True DM digestibility was the best predictor of methane production. Among grain composition parameters, iNDF content was the best predictor of methane production, followed by NDF. Crude fat content also predicted methane production relatively well. Based on the results of this experiment, it can be concluded that replacing barley grain with oat grain in the diet of dairy cows has a potential to lower methane production predicted in vitro. Furthermore, the methane mitigating effect observed in this experiment is at least partly due to the higher fat content and lower digestibility of oats compared to barley.Syftet med denna magistersavhandling var att undersöka huruvida ersättning av kornsäd med havresäd i en diet baserad på gräsensilage innehar potential att sänka den enteriska metanproduktionen från mjölkkor. Spannmålsartens inverkan på in vitro metanproduktion, smältbarhet och produktion av flyktiga fettsyror (VFA) undersöktes samt utfördes en regressionsanalys för att försöka identifiera de bakomliggande mekanismerna för havrens eventuella metansänkande verkan. Studien genomfördes i laboratoriet vid Institutionen för norrländsk jordbruksvetenskap under hösten 2016. För studien användes ett in vitro gasproduktionssystem som bestod av 16 dieter med två replikat, fyra blanka och tre körningar. Varje körning bestod av en tre dagar lång inkubation. Fodermaterialet bestod av 8 sorter av korn, 8 sorter av havre och timotejensilage som inkuberades i glasflaskor enligt 0,5 gram spannmål och 0,5 gram ensilage. Vomvätska samlades in efter morgonutfodring från två mjölkkor av rasen Svensk röd boskap. Gasprovtagning skedde 2, 4, 8, 12, 24, 32 och 48 timmar efter inkubationens start. Sann torrsubstanssmältbarhet mättes genom att tillämpa en 12 dagar lång in situ inkubation i två mjölkkor av rasen Ayrshire. Metanproduktionen uttrycktes som estimerad in vivo och stökiometriskt estimerad metanproduktion. Spannmålsarten hade signifikant inverkan på metanproduktionen. Ersättning av korn med havre minskade både estimerad in vivo och stökiometriskt estimerad metanproduktion. Sort inom spannmålsart hade ingen inverkan på metanproduktionen. Smältbarhet och total VFA-produktion visade sig vara lägre i havredieterna jämfört med korndieterna. Inga skillnader kunde observeras gällande molproportionerna av olika VFA. Sann torrsubstanssmältbarhet var den bästa förklarande variabeln av estimerad in vivo metanproduktion. Bland parametrarna gällande spannmålens sammansättning var iNDF den bästa förklarande variabeln för metanproduktionen. Även NDF-koncentrationen och koncentrationen av fett var signifikanta förklarande variabler. Baserat på resultaten av detta experiment kan man dra slutsatsen att havre som ett utfodringsalternativ till mjölkkor har potential att sänka den enteriska metanproduktionen. Dessutom verkar den sänkande effekten hos havre på metanproduktionen orsakas av den högre fettkoncentrationen och den sämre smältbarheten jämfört med korn. För att undersöka andra möjliga orsaker behövs mer forskning inom ämnet