Effect of tannin-containing hays on enteric methane emissions and nitrogen partitioning in beef cattle1

AbstractThe objective of this study was to determine whether feeding tannin-containing hays to heifers and mature beef cows influences enteric methane (CH4) emissions and nitrogen (N) excretion relative to feeding traditional legume and grass hays. Fifteen mature beef cows (Exp. 1) and 9 yearling heifers (Exp. 2) were each randomly assigned to treatment groups in an incomplete bock design with 2 periods and 6 types of hays with 3 hays fed each period (n = 5 cows and 3 heifers per treatment). Groups were fed tannin-containing [birdsfoot trefoil (BFT), sainfoin (SAN), small burnet (SML)] or non-tannin-containing [alfalfa (ALF), cicer milkvetch (CMV), meadow bromegrass (MB)] hays. Each period consisted of 14 d of adjustment followed by 5 d of sample collection. Nine cows and 9 heifers were selected for the measurement of enteric CH4 emissions (sulfur hexafluoride tracer gas technique), and excretion of feces and urine, while dry matter intake (DMI) was measured for all animals. The concentration of condensed tannins in SAN and BFT was 2.5 ± 0.50% and 0.6 ± 0.09% of dry matter (DM), respectively, while SML contained hydrolyzable tannins (4.5 ± 0.55% of DM). Cows and heifers fed tannin-containing hays excreted less urinary urea N (g/d; P < 0.001) and showed lower concentrations of blood urea N (mg/dL; P < 0.001) than animals fed ALF or CMV, indicating that tannins led to a shift in route of N excretion from urine to feces. Additionally, cows fed either BFT or CMV showed the greatest percentage of retained N (P < 0.001). Enteric CH4 yield (g/kg of DMI) from heifers (P = 0.089) was greatest for MB, while daily CH4 production (g/d) from heifers (P = 0.054) was least for SML. However, digestibility of crude protein was reduced for cows (P < 0.001) and heifers (P < 0.001) consuming SML. The results suggest that tannin-containing hays have the potential to reduce urinary urea N excretion, increase N retention, and reduce enteric CH4 emissions from beef cattle. The non-bloating tannin-free legume CMV may also reduce environmental impacts relative to ALF and MB hays by reducing N excretion in urine and increasing N retention.

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Supplementation with crushed rapeseed causes reduction of methane emissions from lactating dairy cows on pasture

Animal Production Science ◽

10.1071/an15287 ◽

2017 ◽

Vol 57 (1) ◽

pp. 81 ◽

Cited By ~ 4

Author(s):

T. M. Storlien ◽

E. Prestløkken ◽

K. A. Beauchemin ◽

T. A. McAllister ◽

A. Iwaasa ◽

...

Keyword(s):

Dairy Cows ◽

Milk Fat ◽

Dry Matter ◽

Sulfur Hexafluoride ◽

Effective Means ◽

Fat Content ◽

Tracer Gas ◽

Ch4 Emissions ◽

Ch4 Production ◽

Lactating Dairy Cows

The main objective of this study was to investigate the effect of supplementing a pasture diet with crushed rapeseed on enteric methane (CH4) emissions from lactating dairy cows. The experiment was conducted as a crossover design using eight multiparous lactating Norwegian red dairy cows [(means ± s.d.) 548 ± 52 kg bodyweight, 38 ± 14 days in milk and 35 ± 3.7 kg milk/day, at the start of the experiment] maintained in two groups and fed two diets in two periods with the second period extended (18 days) to investigate the persistence of the CH4 response. Four of the eight cows were fitted with a rumen cannula with two cannulated cows assigned to each group. Cows were maintained on pasture (24 h/day) with access to 9 kg/day of concentrate containing 10% crushed rapeseed (RSC) or a control concentrate (CC). Dietary fat content was 63 g/kg dry matter for RSC and 42 g/kg dry matter for CC. The CH4 production was measured for five consecutive days in each period using the sulfur hexafluoride tracer gas technique. Compared with CC, RSC caused a reduction in enteric CH4 emission (221 vs 251 g/day and 8.1 vs 9.0 g/kg of energy-corrected milk), and this response persisted in the extension period. Cows fed RSC had higher milk yield compared with cows fed CC (31.7 vs 29.6 kg/day). However, milk fat and protein content were lower in milk from cows fed RSC than CC. Therefore, energy-corrected milk was not affected by treatment. Feeding RSC lowered milk fat content of palmitic acid compared with CC. The study showed that adding crushed RSC to the diet can be an effective means of reducing CH4 emissions from lactating dairy cows on pasture, without negatively affecting milk production.

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Optimal dose of 3-nitrooxypropanol for decreasing enteric methane emissions from beef cattle fed high-forage and high-grain diets

Animal Production Science ◽

10.1071/an15705 ◽

2018 ◽

Vol 58 (6) ◽

pp. 1049 ◽

Cited By ~ 14

Author(s):

D. Vyas ◽

S. M. McGinn ◽

S. M. Duval ◽

M. K. Kindermann ◽

K. A. Beauchemin

Keyword(s):

Beef Cattle ◽

Energy Intake ◽

Dry Matter ◽

Optimal Dose ◽

Negative Effects ◽

Ch4 Emissions ◽

Ch4 Production ◽

Enteric Methane ◽

Gross Energy ◽

High Forage

The objective of the present study was to determine the dose response of the methane (CH4) inhibitor 3-nitrooxypropanol (NOP) on enteric CH4 production and dry matter intake (DMI) for beef cattle fed a high-forage or high-grain diet. Fifteen crossbred yearling steers were used in two consecutive studies (high-forage backgrounding, high-grain finishing), each designed as an incomplete block with two 28-day periods with a 7-day washout in between and treatments corresponding to six doses of NOP (0 (Control), 50, 75, 100, 150, 200 mg/kg DM). The NOP was provided in the ration daily with the dose increased gradually over the first 10 days of each period. No treatment effects were observed on overall DMI or DMI of cattle when they were in the chambers either for the high-forage (P ≥ 0.54) or high-grain (P ≥ 0.26) diet. With the high-forage diet, NOP supplementation lowered total CH4 emissions (g/day) (P = 0.05), with the response at 200 mg NOP/kg DM different from Control (P < 0.05). Similarly, CH4 emissions corrected for DMI (g/kg DMI) and as a percentage of gross energy intake were linearly reduced in the high-forage diet with supplemental NOP (P < 0.01) and responses observed at 100, 150 and 200 mg NOP/kg DM differed from Control (P < 0.05). For the high-grain diet, total CH4 emissions decreased with incremental increases in the concentration of NOP supplemented (P = 0.04) and responses observed at 150 and 200 mg/kg DM differed from Control. Similarly, linear responses were observed with CH4 emissions corrected for DMI (P = 0.04) and gross energy intake (P = 0.02), with 100–200 mg NOP/kg DM differing from Control. Overall, results from the present study demonstrated that for beef cattle fed high-forage and high-grain diets, supplementation of 100–200 mg NOP/kg DM lowered enteric CH4 emissions without inducing any negative effects on DMI.

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Lawsonia intracellularis infected enterocytes lack sucrase-isomaltase which contributes to reduced pig digestive capacity

Veterinary Research ◽

10.1186/s13567-021-00958-2 ◽

2021 ◽

Vol 52 (1) ◽

Author(s):

Emma T. Helm ◽

Eric R. Burrough ◽

Fernando L. Leite ◽

Nicholas K. Gabler

Keyword(s):

Dry Matter ◽

Post Inoculation ◽

Intestinal Function ◽

Lawsonia Intracellularis ◽

Sample Collection ◽

Treatment Groups ◽

Swine Herds ◽

The Impact ◽

Lesion Severity

AbstractLawsonia intracellularis is endemic to swine herds worldwide, however much is still unknown regarding its impact on intestinal function. Thus, this study aimed to characterize the impact of L. intracellularis on digestive function, and how vaccination mitigates these impacts. Thirty-six L. intracellularis negative barrows were assigned to treatment groups (n = 12/trt): (1) nonvaccinated, L. intracellularis negative (NC); (2) nonvaccinated, L intracellularis challenged (PC); and (3) L. intracellularis challenged, vaccinated (Enterisol® Ileitis, Boehringer Ingelheim) 7 weeks pre-challenge (VAC). On days post-inoculation (dpi) 0 PC and VAC pigs were inoculated with L. intracellularis. From dpi 19–21 fecal samples were collected for apparent total tract digestibility (ATTD) and at dpi 21, pigs were euthanized for sample collection. Post-inoculation, ADG was reduced in PC pigs compared with NC (41%, P < 0.001) and VAC (25%, P < 0.001) pigs. Ileal gross lesion severity was greater in PC pigs compared with NC (P = 0.003) and VAC (P = 0.018) pigs. Dry matter, organic matter, nitrogen, and energy ATTD were reduced in PC pigs compared with NC pigs (P ≤ 0.001 for all). RNAscope in situ hybridization revealed abolition of sucrase-isomaltase transcript in the ileum of PC pigs compared with NC and VAC pigs (P < 0.01). Conversely, abundance of stem cell signaling markers Wnt3, Hes1, and p27Kip1 were increased in PC pigs compared with NC pigs (P ≤ 0.085). Taken together, these data demonstrate that reduced digestibility during L. intracellularis challenge is partially driven by abolition of digestive machinery in lesioned tissue. Further, vaccination mitigated several of these effects, likely from lower bacterial burden and reduced disease severity.

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Within- and between-animal variance in methane emissions in non-lactating dairy cows

Australian Journal of Experimental Agriculture ◽

10.1071/ea07278 ◽

2008 ◽

Vol 48 (2) ◽

pp. 124 ◽

Cited By ~ 34

Author(s):

J. B. Vlaming ◽

N. Lopez-Villalobos ◽

I. M. Brookes ◽

S. O. Hoskin ◽

H. Clark

Keyword(s):

Sulfur Hexafluoride ◽

Energy Levels ◽

Tracer Technique ◽

Ch4 Emissions ◽

Ch4 Production ◽

Lactating Dairy Cows ◽

Coefficients Of Variation ◽

Lactating Dairy Cattle ◽

Over Time

Several studies on methane (CH4) emissions have focussed on selecting high and low CH4-emitting animals. One challenge faced by this work is the lack of consistency, or repeatability, in animal rankings over time. Repeatability for individual animals over time needs to be high to reliably detect high and low CH4-emitting animals. A possible explanation for the lack of repeatability is a relatively high within-animal variation in daily CH4 emissions, meaning that animals could then change their ranking when compared at different points in time. An experiment was undertaken with four non-lactating dairy cattle to assess the within- and between-animal variation in CH4 emissions over time when measured using the sulfur hexafluoride (SF6) tracer technique. Two contrasting diets were fed to the cattle at maintenance energy levels: lucerne silage (diet 1) and a cereal + lucerne + straw mixed ration diet (diet 2). Daily CH4 measurements were undertaken for 23 days on diet 1 and 30 days on diet 2. There was a significant (P < 0.001) difference between diet 1 and diet 2 in daily CH4 production, with mean (±s.e.) production of 124.3 (11.1) g CH4/day from diet 1 and 169.8 (±11.0) g CH4/day from diet 2. Lower CH4 yield (g CH4/kg dry matter intake) was recorded on diet 1 (22.8 ± 2.0) than diet 2 (32.0 ± 2.0). Cows differed significantly (P < 0.05) from one another in daily CH4 yield (diet 1: cow 1 = 19.4 ± 0.6, cow 2 = 22.2 ± 0.8, cow 3 = 23.2 ± 0.7, cow 4 = 25.4 ± 0.6; diet 2: cow 1 = 26.0 ± 0.7, cow 2 = 36.4 ± 0.7, cow 3 = 29.3 ± 0.7, cow 4 = 36.6 ± 0.7). Variances for daily CH4 yield were smaller for diet 1 (within animal = 6.91, between animals = 6.23) than for diet 2 (within animal = 10.09, between animals = 27.79). Estimates of repeatability (variation between animals/total variation) for daily CH4 yield were 47 and 73% in diet 1 and 2, respectively. Coefficients of variation in average daily CH4 emissions in this experiment ranged from 8 to 18% despite the fact that each animal received the same quantity and quality of feed each day. While further research is required, the high within-animal variability in CH4 emissions measured using the SF6 tracer technique may explain why there has been difficulty in obtaining consistent rankings in CH4 yields when animals are measured on multiple occasions. The results also suggest that the SF6 tracer technique may exaggerate apparent between animal differences in CH4 emissions.

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Methane emissions from young and mature dairy cattle

Animal Production Science ◽

10.1071/an15102 ◽

2016 ◽

Vol 56 (11) ◽

pp. 1897 ◽

Cited By ~ 11

Author(s):

C. A. Ramírez-Restrepo ◽

H. Clark ◽

S. Muetzel

Keyword(s):

New Zealand ◽

Emission Factor ◽

Dry Matter ◽

Sulfur Hexafluoride ◽

Dry Matter Intake ◽

Tracer Technique ◽

Ch4 Emissions ◽

Dairy Heifers ◽

Age Related ◽

The Mean

Daily methane (CH4) emissions (g) and CH4 yield (g/kg dry matter intake) were measured from 10 dairy heifers (<1 year old) and nine rumen-fistulated cows (>6 years old) fed ryegrass (Lolium perenne) chaffage indoors. The CH4 emissions were estimated using the sulfur hexafluoride tracer technique in four ~5-day periods beginning in June 2008 and repeated 4, 6 and 7 months later. Respiratory chambers were used in four ~13-day periods beginning in November 2008 and repeated 2, 5 and 6 months later. Third and fourth sulfur hexafluoride tracer periods overlapped with the first and second chamber measurement periods, respectively. Averaged over the four measurement periods the CH4 yields determined using both techniques were similar for heifers and cows. The mean CH4 yield estimated by the sulfur hexafluoride tracer technique was 25.3 ± 0.52 for heifers and 24.1 ± 0.55 for mature cows, whereas the mean CH4 yield measured in respiratory chambers was 23.7 ± 0.66 for heifers and 23.6 ± 0.66 for mature cows. Averaged over the eight measurements irrespective of technique, CH4 yields for heifers (24.5 ± 0.42) and cows (23.8 ± 0.43) were similar. There was also no difference between CH4 methods for assessing CH4 yield during the overlapping measurement periods. It was concluded that no consistent differences in CH4 yield existed between heifers and mature cows. Therefore, we do not recommend adoption of an age-related emission factor for cattle in the national inventory calculations for New Zealand.

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330 3-nitrooxypropanol Supplementation of a Forage Diet Decreased Enteric Methane Emissions from Beef Cattle Without Affecting Apparent Total-tract Digestibility

Journal of Animal Science ◽

10.1093/jas/skab235.338 ◽

2021 ◽

Vol 99 (Supplement_3) ◽

pp. 186-187

Author(s):

Aklilu Alemu ◽

Xiu Min Zhang ◽

Maik Kindermann ◽

Karen A Beauchemin

Keyword(s):

Crude Protein ◽

Dry Matter ◽

Control Diet ◽

Nutrient Digestibility ◽

Ch4 Emissions ◽

Ruminal Ph ◽

Enteric Methane ◽

Ruminant Diets ◽

Dietary Treatments ◽

High Forage

Abstract Supplementation of ruminant diets with the investigational methane (CH4) inhibitor 3-nitrooxypropanol (3-NOP; DSM Nutritional Products, Switzerland) is as a promising mitigation strategy. However, most studies have examined high grain or mixed forage-concentrate diets. The objective of this study was to evaluate the effects of supplementing a forage diet with 3-NOP on rumen fermentation, CH4 emissions and apparent total-tract nutrient digestibility. Eight ruminally cannulated beef heifers (BW = 514 kg) were randomly allocated to two treatments in a crossover design with 49-d periods. Dietary treatments were: control, high-forage diet (90% forage DM basis) without 3-NOP; and NOP, control diet supplemented with 150 mg 3-NOP/kg DM. After a 14-d diet adaption, dry matter (DM) intake (DMI) was recorded daily. Rumen contents were collected on days 17 and 28 for volatile fatty acid (VFA) analysis, whereas ruminal pH was continuously monitored from day 20 to 27. Diet digestibility was measured on day 38 to 41 by total collection of feces. Enteric CH4 emissions were measured on days 46 to 49 in chambers. Dry matter intake was lower (P = 0.001) for NOP (10.0 kg/d) as compared with control (10.2 kg/d). However, DM, neutral and acid detergent fiber, and crude protein digestibilities were similar between treatments (P ≥ 0.29). Although total VFA concentration was not affected by treatment (P = 0.19), the reduction in acetate and increase in propionate proportion for NOP lowered (P < 0.001) the acetate to propionate ratio by 18% as compared with control. Mean pH was lower (P = 0.03) for control (6.46) than NOP (6.57). Furthermore, CH4 yield (g/kg DMI) was 21.6% less (P < 0.001) for NOP relative to control (25.5 g/kg DMI). Overall, the results indicate that enteric CH4 emissions were effectively decreased with 3-NOP supplementation of a forage diet without affecting apparent total-tract digestibility of nutrients.

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Effect of Mootral—a garlic- and citrus-extract-based feed additive—on enteric methane emissions in feedlot cattle

Translational Animal Science ◽

10.1093/tas/txz133 ◽

2019 ◽

Vol 3 (4) ◽

pp. 1383-1388 ◽

Cited By ~ 1

Author(s):

Breanna M Roque ◽

Henk J Van Lingen ◽

Hilde Vrancken ◽

Ermias Kebreab

Keyword(s):

Beef Cattle ◽

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

Experimental Period ◽

Feed Additive ◽

Gas Emissions ◽

Ch4 Emissions ◽

Ch4 Production ◽

Enteric Methane

Abstract: Enteric methane (CH4) production is the main source of greenhouse gas emissions from livestock globally with beef cattle contributing 5.95% of total global greenhouse gas emissions. Various mitigation strategies have been developed to reduce enteric emissions with limited success. In vitro studies have shown a reduction in CH4 emissions when using garlic and citrus extracts. However, there is paucity of data regarding in vivo studies investigating the effect of garlic and citrus extracts in cattle. The objective of this study was to quantitatively evaluate the response of Angus × Hereford cross steers consuming the feed additive Mootral, which contains extracts of both garlic and citrus, on CH4 yield (g/kg dry matter intake [DMI]). Twenty steers were randomly assigned to two treatments: control (no additive) and Mootral supplied at 15 g/d in a completely randomized design with a 2-wk covariate and a 12-wk data collection periods. Enteric CH4 emissions were measured using the GreenFeed system during the covariate period and experimental weeks 2, 6, 9, and 12. CH4 yield (g/kg DMI) by steers remained similar in both treatments for weeks 2 to 9. In week 12, there was a significant decrease in CH4 yield (23.2%) in treatment compared to control steers mainly because the steers were consuming all the pellets containing the additive. However, overall CH4 yield (g/kg DMI) during the entire experimental period was not significantly different. Carbon dioxide yield (g/kg DMI) and oxygen consumption (g/kg DMI) did not differ between treatments during the entire experimental period. DMI, average daily gain, and feed efficiency also remained similar in control and supplemented steers. The in vivo results showed that Mootral may have a potential to be used as a feed additive to reduce enteric CH4 production and yield in beef cattle but needs further investigation under various dietary regimen.

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PSXI-29 Assessing enteric methane emissions from Nellore and Angus-Nellore crossbred cattle in a tropical, intensive beef cattle production system

Journal of Animal Science ◽

10.1093/jas/skz258.757 ◽

2019 ◽

Vol 97 (Supplement_3) ◽

pp. 380-381

Author(s):

Isabella Cristina F Maciel ◽

Fabiano A Barbosa ◽

Thierry R Tomich ◽

Ramon C Alvarenga ◽

Ludhiana R Ferreira ◽

...

Keyword(s):

Beef Cattle ◽

Sulfur Hexafluoride ◽

Methane Emissions ◽

Ch4 Production ◽

Trial Onset ◽

Enteric Methane ◽

Grazing Period ◽

Tropical Climates ◽

The Impact ◽

Enteric Methane Emissions

Abstract Crossbreeding has been used to improve performance in beef cattle; however, the effects of breed composition on methane production, yield and intensity from cattle in a tropical intensive system remain unknown. To assess the impact of breed composition on enteric methane emissions, Nellore (NE; yr 1: BW = 171.5 ± 19.4 kg; n = 10; yr 2: BW = 215.8 ± 32.3 kg, n = 25) and Angus-Nellore crossbred (AN; yr 1: BW = 214.2 ± 26.4 kg, n = 10; yr 2: BW = 242.5 ± 32.2 kg, n = 25) were compared. At trial onset, 10 mo old steers grazed Megathyrsus maximus ‘Mombaça’ in the grazing period (GP) and then were finished in a feedlot (FL) (35:65% corn silage:concentrate diet). Steers (n = 8) from each breed composition were randomly selected in GP and FL to measure CH4 production using a sulfur hexafluoride technique and DMI using titanium dioxide. The NE produced 19% less CH4 than AN in GP (17.21 vs 21.17 kg, P < 0.01), and no difference was observed in FL (22.34 vs 22.67 kg, P > 0.10). However, in FL, NE had greater CH4 intensity (CH4/ADG) compared to AN (122.76 vs 97.49 g/kg, P < 0.01). Furthermore, CH4/carcass weight was greater for NE than AN (0.079 vs 0.067 g/kg CW, P < 0.01). Breed composition did not influence CH4 yield (CH4/DMI) in either phase. The percentage CH4/GEI (Ym) for GP was higher for AN than NE (4.5 vs 3.8%), but lower than the IPCC recommended Ym of 6.5%. In FL, Ym was similar between breed composition (5.0%) and greater than the IPCC Ym of 3%. In our study the introduction of Angus into Nellore has potential to reduce CH4 intensity in tropical climates, resulting in less methane emission per kg beef produced.

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Enteric methane emissions in response to ruminal inoculation of Propionibacterium strains in beef cattle fed a mixed diet

Animal Production Science ◽

10.1071/an14801 ◽

2016 ◽

Vol 56 (7) ◽

pp. 1035 ◽

Cited By ~ 6

Author(s):

D. Vyas ◽

A. Alazzeh ◽

S. M. McGinn ◽

T. A. McAllister ◽

O. M. Harstad ◽

...

Keyword(s):

Fatty Acids ◽

Volatile Fatty Acids ◽

Basal Diet ◽

Barley Grain ◽

Mixed Diet ◽

Beef Heifers ◽

Ch4 Emissions ◽

Ch4 Production ◽

Enteric Methane ◽

Barley Silage

The objective of this study was to test the efficacy of Propionibacterium strains to mitigate enteric methane (CH4) emissions in beef heifers fed a mixed diet. An experiment was conducted with 16 ruminally cannulated beef heifers fed a basal diet consisting of 60 : 40 barley silage : barley grain (DM basis). Treatments included: (1) Control, (2) Propionibacterium freudenreichii T114, (3) P. thoenii T159, and (4) P. freudenreichii T54. Strains (1 × 1011 colony forming units) were administered daily directly into the rumen before feeding. No treatment effects were observed for DM intake (P = 0.90), mean ruminal pH (P = 0.50) and total volatile fatty acids (P = 0.44). However, compared with the Control, proportions of individual volatile fatty acids changed with acetate being less with Propionibacterium T159 (P = 0.02), whereas ruminal isobutyrate (P < 0.01) and acetate : propionate ratio (P = 0.04) were greater with Propionibacterium T114. Total daily enteric CH4 production averaged 188 g/day and was not affected by Propionbacterium strains (P = 0.51). Methane yield averaged 22 g/kg of DMI intake and tended to be greater with Propionibacterium strains (P = 0.08). The relative abundance of total Propionibacteria was greater with the inoculation of Propionibacterium T159 relative to the Control heifers (P = 0.04). In conclusion, inoculation of Propionibacterium T159 decreased ruminal acetate proportion and Propionibacterium T114 increased acetate : propionate ratio. However, inoculated strains failed to lower total CH4 emissions possibly due to the inability of Propionibacterium strains to elevate ruminal propionate concentrations.

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A meta-analysis comparing four measurement methods to determine the relationship between methane emissions and dry-matter intake in New Zealand dairy cattle

Animal Production Science ◽

10.1071/an18573 ◽

2020 ◽

Vol 60 (1) ◽

pp. 96 ◽

Cited By ~ 2

Author(s):

Arjan Jonker ◽

Peter Green ◽

Garry Waghorn ◽

Tony van der Weerden ◽

David Pacheco ◽

...

Keyword(s):

New Zealand ◽

Dairy Cattle ◽

Dry Matter ◽

Measurement Methods ◽

Dry Matter Intake ◽

Residual Variance ◽

Mixed Effect ◽

Ch4 Emissions ◽

Ch4 Production ◽

The Relationship

Enteric methane (CH4) emissions and dry-matter intake (DMI) can be accurately and precisely measured in respiration chambers (RC), whereas automated head chambers (GreenFeed; GF) and the SF6 tracer method can provide estimates of CH4 emissions from grazing cattle. In New Zealand, most dairy cattle graze pasture and, under these conditions, DMI also has to be estimated. The objective of the current study was to compare the relationship between CH4 production and DMI of New Zealand dairy cattle fed forages using the following four measurement methods: RC with measured DMI (RC); sulfur hexafluoride (SF6) with measured DMI (SF6-DMI); SF6 with DMI estimated from prediction equations or indigestible markers (SF6); GF with measured or estimated DMI (GF). Data were collected from published literature from New Zealand trials with growing and lactating dairy cattle fed forage-based diets and data were analysed using a mixed-effect model. The intercept of the linear regression between CH4 production and DMI was not significantly different from zero and was omitted from the model. However, residual variance (observed–predicted values) increased with an increasing DMI, which was addressed by log-transforming CH4 per unit of DMI and this model was used for final data analysis. The accuracy of the four methods for predicting log CH4 per unit of DMI was similar (P = 0.55), but the precision (indicated by residuals) differed (P < 0.001) among methods. The residual standard deviations for SF6, GF and SF6-DMI were 4.6, 3.4 and 2.1 times greater than the residuals for RC. Hence, all methods enabled accurate prediction of CH4 per unit of DMI, but methodology for determining both CH4 and DMI affected their precision (residuals).

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