RESUMEN
To meet the 1.5 °C target, methane (CH4) from ruminants must be reduced by 11 to 30% by 2030 and 24 to 47% by 2050 compared to 2010 levels. A meta-analysis identified strategies to decrease product-based (PB; CH4 per unit meat or milk) and absolute (ABS) enteric CH4 emissions while maintaining or increasing animal productivity (AP; weight gain or milk yield). Next, the potential of different adoption rates of one PB or one ABS strategy to contribute to the 1.5 °C target was estimated. The database included findings from 430 peer-reviewed studies, which reported 98 mitigation strategies that can be classified into three categories: animal and feed management, diet formulation, and rumen manipulation. A random-effects meta-analysis weighted by inverse variance was carried out. Three PB strategiesnamely, increasing feeding level, decreasing grass maturity, and decreasing dietary forage-to-concentrate ratiodecreased CH4 per unit meat or milk by on average 12% and increased AP by a median of 17%. Five ABS strategiesnamely CH4 inhibitors, tanniferous forages, electron sinks, oils and fats, and oilseedsdecreased daily methane by on average 21%. Globally, only 100% adoption of the most effective PB and ABS strategies can meet the 1.5 °C target by 2030 but not 2050, because mitigation effects are offset by projected increases in CH4 due to increasing milk and meat demand. Notably, by 2030 and 2050, low- and middle-income countries may not meet their contribution to the 1.5 °C target for this same reason, whereas high-income countries could meet their contributions due to only a minor projected increase in enteric CH4 emissions.
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Metano , Rumiantes , África , Animales , Países en Desarrollo , Europa (Continente) , Calentamiento Global/prevención & control , Metano/análisisRESUMEN
Direct measurements of methane (CH4) from individual animals are difficult and expensive. Predictions based on proxies for CH4 are a viable alternative. Most prediction models are based on multiple linear regressions (MLR) and predictor variables that are not routinely available in commercial farms, such as dry matter intake (DMI) and diet composition. The use of machine learning (ML) algorithms to predict CH4 emissions from across-country heterogeneous data sets has not been reported. The objectives were to compare performances of ML ensemble algorithm random forest (RF) and MLR models in predicting CH4 emissions from proxies in dairy cows, and assess effects of imputing missing data points on prediction accuracy. Data on CH4 emissions and proxies for CH4 from 20 herds were provided by 10 countries. The integrated data set contained 43,519 records from 3,483 cows, with 18.7% missing data points imputed using k-nearest neighbor imputation. Three data sets were created, 3k (no missing records), 21k (missing DMI imputed from milk, fat, protein, body weight), and 41k (missing DMI, milk fat, and protein records imputed). These data sets were used to test scenarios (with or without DMI, imputed vs. nonimputed DMI, milk fat, and protein), and prediction models (RF vs. MLR). Model predictive ability was evaluated within and between herds through 10-fold cross-validation. Prediction accuracy was measured as correlation between observed and predicted CH4, root mean squared error (RMSE) and mean normalized discounted cumulative gain (NDCG). Inclusion of DMI in the model improved within and between-herd prediction accuracy to 0.77 (RMSE = 23.3%) and 0.58 (RMSE = 31.9%) in RF and to 0.50 (RMSE = 0.327) and 0.13 (RMSE = 42.71) in MLR, respectively than when DMI was not included in the predictive model. When missing DMI records were imputed, within and between-herd accuracy increased to 0.84 (RMSE = 18.5%) and 0.63 (RMSE = 29.9%), respectively. In all scenarios, RF models out-performed MLR models. Results suggest routinely measured variables from dairy farms can be used in developing globally robust prediction models for CH4 if coupled with state-of-the-art techniques for imputation and advanced ML algorithms for predictive modeling.
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Lactancia , Metano , Animales , Bovinos , Dieta/veterinaria , Femenino , Intestino Delgado/metabolismo , Metano/metabolismo , Leche/químicaRESUMEN
Sieve analyses of hindgut contents of horses as well as observations in horses where plastic markers had been applied to a caecal cannula suggested that there may be a discrimination by particle size in the passage or retention of digesta. Here, we performed a similar experiment with five caecum-cannulated horses (562 ± 31 kg) fed a constant amount (6.81 kg dry matter/day) of grass hay. Passage markers representing the liquid (Co-EDTA) as well as the particulate digesta phase (Yb-undefined; Cr mordanted fibre 1-2 mm; Ce-mordanted fibre 8 mm) were given as a pulse-dose into the cannula to measure their mean retention times (MRT). The MRTs were compared by repeated-measurements analysis of variance. The MRT in the hindgut was 22.2 ± 2.4 h for Co, 25.0 ± 3.4 h for Yb, 26.2 ± 1.6 h for Cr and 26.3 ± 1.5 h for Ce. Whereas differences between the particle marker MRTs were not significant (padj. > 0.05), significant differences were observed between the solute marker Co and each of the particle markers Cr and Ce (padj. < 0.009). The results confirm the well-known significant, albeit small, difference in MRT in horses between the fluid and the particle digesta phase, and corroborate another recent study that used a combination of whole, marked hay and individual marker analysis in different particle size fractions of the faeces, which also did not detect a selective retention of any particle size class.
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Ciego , Caballos , Tamaño de la Partícula , Animales , Alimentación Animal , Ciego/anatomía & histología , Ciego/fisiología , Fibras de la Dieta/administración & dosificación , Fibras de la Dieta/análisis , Digestión , Heces/química , Caballos/anatomía & histología , Cateterismo/veterinariaRESUMEN
The capybara (Hydrochoerus hydrochaeris), the largest living rodent, probably has a "mucus-trap" colonic separation mechanism. To test this hypothesis, we measured the mean retention time of a solute marker (MRTSolute ), 2 mm (MRT2 mm ), 10 mm (MRT10 mm ), and 20 mm (MRT20 mm ) particle markers and nutrient digestibility in adult captive capybaras (27-52 kg body mass (BM), 2-11 yr). In addition, total gut fill and the selectivity factor (MRTSolute /MRT2 mm ) were calculated, and mean faecal particle size and metabolic fecal nitrogen of captive capybaras were compared to those of free-ranging specimens. Finally, we also measured methane production in one animal. The MRT2 mm (29.2 ± 8.2 hr) was different (p < 0.01) from MRTSolute (37.0 ± 13.1 hr), MRT10 mm (36.5 ± 8.2 hr), and MRT20 mm (35.1 ± 9.6 hr). The selectivity factor (1.26 ± 0.30) was in the range considered typical for a "mucus-trap" colonic separation mechanism. The estimated total gut fill was 1.50 ± 0.37% and 1.73 ± 0.25% of BM calculated from the results of the 2-mm and 10-mm particle markers, respectively. The CH4 emission was 13.7 L/day. Captive capybaras had greater mean fecal particle size (0.44 ± 0.06 vs. 0.29 ± 0.05 mm, p < 0.001) and metabolic fecal nitrogen (65.5 ± 3.91 vs. 46.8 ± 10.5% of fecal nitrogen, p < 0.001) than free-ranging capybaras. Organic matter digestibility decreased less steeply with increasing dietary crude fiber content in capybaras as compared to published data from rabbits or guinea pigs. Accordingly, the digestive physiology of the capybara is characterized by a comparatively high fiber digestibility, with a "mucus-trap" colonic separation mechanism, allowing capybaras to thrive on forage-only diets.
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Animales de Zoológico , Digestión/fisiología , Roedores/fisiología , Animales , Heces/química , Femenino , Tránsito Gastrointestinal , Masculino , Metano , Roedores/anatomía & histologíaRESUMEN
Enteric methane (CH4 ) production from cattle contributes to global greenhouse gas emissions. Measurement of enteric CH4 is complex, expensive, and impractical at large scales; therefore, models are commonly used to predict CH4 production. However, building robust prediction models requires extensive data from animals under different management systems worldwide. The objectives of this study were to (1) collate a global database of enteric CH4 production from individual lactating dairy cattle; (2) determine the availability of key variables for predicting enteric CH4 production (g/day per cow), yield [g/kg dry matter intake (DMI)], and intensity (g/kg energy corrected milk) and their respective relationships; (3) develop intercontinental and regional models and cross-validate their performance; and (4) assess the trade-off between availability of on-farm inputs and CH4 prediction accuracy. The intercontinental database covered Europe (EU), the United States (US), and Australia (AU). A sequential approach was taken by incrementally adding key variables to develop models with increasing complexity. Methane emissions were predicted by fitting linear mixed models. Within model categories, an intercontinental model with the most available independent variables performed best with root mean square prediction error (RMSPE) as a percentage of mean observed value of 16.6%, 14.7%, and 19.8% for intercontinental, EU, and United States regions, respectively. Less complex models requiring only DMI had predictive ability comparable to complex models. Enteric CH4 production, yield, and intensity prediction models developed on an intercontinental basis had similar performance across regions, however, intercepts and slopes were different with implications for prediction. Revised CH4 emission conversion factors for specific regions are required to improve CH4 production estimates in national inventories. In conclusion, information on DMI is required for good prediction, and other factors such as dietary neutral detergent fiber (NDF) concentration, improve the prediction. For enteric CH4 yield and intensity prediction, information on milk yield and composition is required for better estimation.
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Agricultura/métodos , Bovinos/fisiología , Metano/análisis , Leche/estadística & datos numéricos , Animales , Australia , Bases de Datos Factuales , Ingestión de Alimentos , Europa (Continente) , Unión Europea , Femenino , Lactancia , Metano/metabolismo , Leche/metabolismo , Modelos Teóricos , Estados UnidosRESUMEN
BACKGROUND: A limited availability of microbial protein can impair productivity in ruminants. Ruminal nitrogen efficiency might be optimised by combining high-quality forage legumes such as red clover (RC), which has unfavourably high ruminal protein degradability, with tanniferous legumes like sainfoin (SF) and birdsfoot trefoil (BT). Silages from SF and from BT cultivars [Bull (BB) and Polom (BP)] were incubated singly or in combination with RC using the Rumen Simulation Technique (n = 6). RESULTS: The tanniferous legumes, when compared to RC, changed the total short-chain fatty acid profile by increasing propionate proportions at the expense of butyrate. Silage from SF contained the most condensed tannins (CTs) (136 g CT kg-1 dry matter) and clearly differed in various traits from the BT and RC silages. The apparent nutrient degradability (small with SF), microbial protein synthesis, and calculated content of potentially utilisable crude protein (large with SF) indicated that SF had the greatest efficiency in ruminal protein synthesis. The effects of combining SF with RC were mostly linear. CONCLUSION: The potential of sainfoin to improve protein supply, demonstrated either individually or in combination with a high-performance forage legume, indicates its potential usefulness in complementing protein-deficient ruminant diets and high-quality forages rich in rumen-degradable protein. © 2017 Society of Chemical Industry.
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Alimentación Animal/análisis , Bacterias/metabolismo , Proteínas Bacterianas/metabolismo , Bovinos/metabolismo , Fabaceae/metabolismo , Nitrógeno/metabolismo , Rumen/metabolismo , Rumen/microbiología , Animales , Digestión , Fabaceae/química , Fabaceae/clasificación , Femenino , Microbioma Gastrointestinal , Lactancia , Leche/metabolismo , Proantocianidinas/análisis , Proantocianidinas/metabolismoRESUMEN
This in vitro study examined the ability of important immune modulators [ß-hydroxybutyrate (BHB), cortisol, prolactin, isoproterenol and insulin] to influence the responsiveness of peripheral blood mononuclear cells (PBMC) from multiparous dairy cows 29 ± 2 days before and 14 ± 3 days after calving. The activation and proliferation of PBMC in response to the mitogen phytohemagglutinin was estimated by the oxygen consumption rate after 24 hr and the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5diphenyl tetrazolium bromide) method after 72 hr respectively. In early lactation, the presence of 2 compared to 0.5 mmol/L BHB reduced PBMC activation (p < 0.05) and proliferation (p < 0.10), and the presence of 0.7 compared to 0.2 ng/ml insulin enhanced (p < 0.10) PBMC proliferation. In dry cows, the presence of low concentrations of BHB and insulin and both concentrations of prolactin (20 vs. 300 ng/ml) and isoproterenol (70 vs. 130 ng/L) enhanced activation (p < 0.10), but not proliferation (p ≥ 0.10) compared to cultures with no modulator addition. The presence or absence of high or low concentrations of hydrocortisone (20 vs. 45 nmol/L) did not (p ≥ 0.10) influence the activation and proliferation of PBMC from dry and early lactating cows. It is tempting to speculate that in antepartum PBMC the modulators represented an energy source or positive extrinsic signals to use nutrients for the activation process. On the other hand, PBMC from postpartum cows are known to be exposed to a metabolic challenging endocrine background. Under such conditions, high BHB concentrations and high insulin concentrations seem to act as negative and positive signals for PBMC, respectively, to utilize nutrients for activation and proliferation.
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Bovinos/fisiología , Proliferación Celular/efectos de los fármacos , Factores Inmunológicos/farmacología , Leucocitos Mononucleares/efectos de los fármacos , Animales , Bovinos/sangre , Células Cultivadas , Femenino , Lactancia , Leucocitos Mononucleares/metabolismo , Paridad , Periodo Periparto , EmbarazoRESUMEN
BACKGROUND: Dietary supplementation with oilseeds can reduce methane emission in ruminants, but only a few common seeds have been tested so far. This study tested safflower (Carthamus tinctorius), poppy (Papaver somniferum), hemp (Cannabis sativa), and camelina (Camelina sativa) seeds in vitro using coconut (Cocos nucifera) oil and linseed (Linum usitatissimum) as positive controls. RESULTS: All the tested oilseeds suppressed methane yield (mL g-1 dry matter, up to 21%) compared to the non-supplemented control when provided at 70 g oil kg-1 dry matter, and they were as effective as coconut oil. Safflower and hemp were more effective than linseed (21% and 18% vs. 10%), whereas the effects of poppy and camelina were similar to linseed. When methane was related to digestible organic matter, only hemp and safflower seeds and coconut oil were effective compared to the non-supplemented control (up to 11%). The level of methanogenesis and the ratios of either the n-6:n-3 fatty acids or C18:2 :C18:3 in the seed lipids were not related. CONCLUSION: Unconventional oilseeds widen the spectrum of oilseeds that can be used in dietary methane mitigation. In vivo confirmation of their methane mitigating effect is still needed, and their effects on animal performance still must be determined. © 2017 Society of Chemical Industry.
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Alimentación Animal/análisis , Brassicaceae/metabolismo , Cannabis/metabolismo , Carthamus tinctorius/metabolismo , Metano/metabolismo , Papaver/metabolismo , Aceites de Plantas/metabolismo , Rumen/metabolismo , Animales , Brassicaceae/química , Cannabis/química , Carthamus tinctorius/química , Bovinos , Suplementos Dietéticos/análisis , Fermentación , Metano/análisis , Modelos Biológicos , Papaver/química , Aceites de Plantas/química , Semillas/química , Semillas/metabolismoRESUMEN
Low-protein diets are increasingly being used in dairy cow nutrition to minimise noxious nitrogen (N) emissions. However, at parturition, the lower milk yield at that time may mask deficiency in dietary utilisable crude protein (uCP; equivalent to metabolisable protein). Under restrictive feeding conditions, farmers would limit the feed allowance to match the lower measured milk yield, thereby exacerbating the deficiency. The consequences for N emission intensity per kg milk yield and methane emissions are unknown. In this study, two diets were fed to nine Holstein cows each from parturition onwards. One diet was complete and the other was calculated as 20% deficient in uCP. Feed allowance was always oriented towards the measured milk yield. In each of the first eight lactation weeks, intake and excretion were measured for 5 d. On the last 2 d of this period, methane emission was measured in respiration chambers. The statistical model included treatment, week and interaction as effects. The real levels of uCP and energy supply across the 8 weeks were 33% and 15% below requirements, respectively, in the Deficient cows. In addition, the Deficient cows consumed 18% less dry matter (caused by substantial refusals in week 1, where energy supply was according to requirements) and produced 25% less milk (26 vs. 34 kg/d). Cows in both groups used dietary N with similar efficiency for milk protein synthesis and excreted similar proportions of the N ingested via urine and faeces. This resulted in both treatments having similar N emission intensities per kg milk N and similar urinary N as a proportion of total excreta N, suggesting a similar potential for gaseous N emissions from the manure per kg of milk. The Deficient cows emitted 22% less methane overall but had similar methane yield and emission intensity to the Controls. In conclusion, a reduction in crude protein intake immediately after parturition does not reduce N emission per unit of milk when associated with uCP deficiency.
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Bovinos/metabolismo , Dieta con Restricción de Proteínas/veterinaria , Leche/metabolismo , Nitrógeno/metabolismo , Alimentación Animal/análisis , Animales , Dieta/veterinaria , Proteínas en la Dieta/administración & dosificación , Femenino , Lactancia , Metano/metabolismo , Nitrógeno/orina , Distribución AleatoriaRESUMEN
Enteric methane (CH4) production is a side-effect of herbivore digestion, but it is unknown whether CH4 itself influences digestive physiology. We investigated the effect of adding CH4 to, or reducing it in, the reticulorumen (RR) in a 4×4 Latin square experiment with rumen-fistulated, non-lactating cows, with four treatments: (i) control, (ii) insufflation of CH4 (iCH4), (iii) N via rumen fistula, (iv) reduction of CH4 via administration of bromochloromethane (BCM). DM intake (DMI), apparent total tract digestibility, digesta mean retention times (MRT), rumen motility and chewing activity, spot breath CH4 emission (CH4exhal, litre/kg DMI) as well as CH4 dissolved in rumen fluid (CH4RRf, µg/ml) were measured. Data were analysed using mixed models, including treatment (or, alternatively, CH4exhal or CH4RRf) and DMI relative to body mass0·85 (rDMI) as covariates. rDMI was the lowest on the BCM treatment. CH4exhal was highest for iCH4 and lowest for BCM treatments, whereas only BCM affected (reduced) CH4RRf. After adjusting for rDMI, CH4RRf had a negative association with MRT in the gastrointestinal tract but not in the RR, and negative associations with fibre digestibility and measures of rumination activity. Adjusting for rDMI, CH4exhal had additionally a negative association with particle MRT in the RR and a positive association with rumen motility. Thus, higher rumen levels of CH4 (CH4exhal or CH4RRf) were associated with shorter MRT and increased motility. These findings are tentatively interpreted as a feedback mechanism in the ruminant digestive tract that aims at mitigating CH4 losses by shortening MRT at higher CH4.
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Bovinos/fisiología , Motilidad Gastrointestinal/fisiología , Metano/metabolismo , Rumen/fisiología , Animales , Heces , Femenino , Contenido Digestivo , Concentración de Iones de Hidrógeno , MasticaciónRESUMEN
Digesta flow plays an important role in ruminant digestive physiology. We measured the mean retention time (MRT) of a solute and a particle marker in the gastrointestinal tract (GIT) and the reticulorumen (RR) of five gazelles and one dikdik species. Species-specific differences were independent from body mass (BM) or food intake. Comparative evaluations (including up to 31 other ruminant species) indicate that MRT GIT relate positively to BM, and are less related to feeding type (the percentage of grass in the natural diet, %grass) than MRT RR. The MRTparticleRR is related to BM and (as a trend) %grass, matching a higher RR capacity with increasing BM in grazers compared to browsers. MRTsoluteRR is neither linked to BM nor to %grass but shows a consistent phylogenetic signal. Selectivity factors (SF; MRTparticle/MRTsolute, proxies for the degree of digesta washing) are positively related to %grass, with a threshold effect, where species with >20% grass have higher SF. These findings suggest that in different ruminant taxa, morphophysiological adaptations controlling MRTsoluteRR evolved to achieve a similar SF RR in relation to a %grass threshold. A high SF could facilitate an increased microbial yield from the forestomach. Reasons for variation in SF above the %grass threshold might represent important drivers of ruminant diversification and await closer investigation.
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Antílopes/fisiología , Rumen/fisiología , Adaptación Fisiológica , Animales , Peso Corporal , Dieta , Digestión , Ingestión de Alimentos , Tracto Gastrointestinal/fisiología , Cinética , Masculino , Filogenia , Especificidad de la EspecieRESUMEN
The aim of the present experiment was to compare silage prepared from maize having a brown midrib (BMR) mutation with control (CTR) maize to identify their effects on enteric methane emission, digesta mean retention time (MRT), ruminal fermentation and digestibility. In addition, the utility of archaeol present in faecal samples was validated as a proxy for methane production. Seven German Holstein heifers were fed total mixed rations with a maize-silage proportion (either BMR or CTR) of 920 g/kg dry matter (DM) in a change-over design. Heifers were fed boluses with markers to measure MRT; faeces were collected for 7 days and rumen fluid was collected on the penultimate day. Methane emission was measured in respiration chambers on one day. Data were analysed by t-test and regression analysis. DM intake did not differ between the two diets. The apparent digestibility of DM and most nutrients was unaffected by diet type, but apparent digestibility of neutral and acid detergent-fibre was higher in those heifers fed BMR than in those fed CTR. Comparisons between diets revealed no difference in particle or solute MRT in the gastro-intestinal tract and the reticulorumen. Concentrations of short-chain fatty acid and ammonia in rumen fluid and its pH were not affected by silage type. Independent of the mode of expression [l/d, l/kg DM intake, l/kg digested organic matter], methane emissions were not affected by maize-silage type, but with BMR, there was a trend towards lower methane production per unit of digested neutral detergent fibre than there was with CTR silage. Results of the present study show that feeding heifers BMR silage does not increase methane emissions despite a higher fibre digestibility as compared to CTR silage. Therefore, it is assumed that improvements in animal productivity achieved by feeding BMR silage, as some studies have reported, can be obtained without extra environmental cost per unit of milk or meat. Neither faecal archaeol content [µg/g] nor daily amount excreted [mg/d] is suitable to predict methane production in absolute terms [l per day]. However, faecal archaeol content has a certain potential for predicting the methane yield [l per kg DM intake] of individual animals.
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Bovinos/fisiología , Éteres de Glicerilo/análisis , Metano/biosíntesis , Rumen/metabolismo , Zea mays/clasificación , Fenómenos Fisiológicos Nutricionales de los Animales , Animales , Dieta/veterinaria , Digestión , Heces/química , Femenino , Ensilaje/análisisRESUMEN
Differences in allometric scaling of physiological characters have the appeal to explain species diversification and niche differentiation along a body mass (BM) gradient - because they lead to different combinations of physiological properties, and thus may facilitate different adaptive strategies. An important argument in physiological ecology is built on the allometries of gut fill (assumed to scale to BM(1.0)) and energy requirements/intake (assumed to scale to BM(0.75)) in mammalian herbivores. From the difference in exponents, it has been postulated that the mean retention time (MRT) of digesta should scale to BM(1.0-0.75)=BM(0.25). This has been used to argue that larger animals have an advantage in digestive efficiency and hence can tolerate lower-quality diets. However, empirical data does not support the BM(0.25) scaling of MRT, and the deduction of MRT scaling implies, according to physical principles, no scaling of digestibility; basing assumptions on digestive efficiency on the thus-derived MRT scaling amounts to circular reasoning. An alternative explanation considers a higher scaling exponent for food intake than for metabolism, allowing larger animals to eat more of a lower quality food without having to increase digestive efficiency; to date, this concept has only been explored in ruminants. Here, using data for 77 species in which intake, digestibility and MRT were measured (allowing the calculation of the dry matter gut contents (DMC)), we show that the unexpected shallow scaling of MRT is common in herbivores and may result from deviations of other scaling exponents from expectations. Notably, DMC have a lower scaling exponent than 1.0, and the 95% confidence intervals of the scaling exponents for intake and DMC generally overlap. Differences in the scaling of wet gut contents and dry matter gut contents confirm a previous finding that the dry matter concentration of gut contents decreases with body mass, possibly compensating for the less favorable volume-surface ratio in the guts of larger organisms. These findings suggest that traditional explanations for herbivore niche differentiation along a BM gradient should not be based on allometries of digestive physiology. In contrast, they support the recent interpretation that larger species can tolerate lower-quality diets because their intake has a higher allometric scaling than their basal metabolism, allowing them to eat relatively more of a lower quality food without having to increase digestive efficiency.
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Peso Corporal , Digestión , Ingestión de Alimentos/fisiología , Tracto Gastrointestinal/fisiología , Herbivoria/fisiología , Mamíferos/fisiología , Adaptación Fisiológica , Animales , Intervalos de Confianza , Bases de Datos Factuales , Fermentación , Análisis de los Mínimos Cuadrados , Tamaño de los Órganos , Filogenia , Especificidad de la Especie , Factores de TiempoRESUMEN
Methane (CH4) emissions from ruminants are of a significant environmental concern, necessitating accurate prediction for emission inventories. Existing models rely solely on dietary and host animal-related data, ignoring the predicting power of rumen microbiota, the source of CH4. To address this limitation, we developed novel CH4 prediction models incorporating rumen microbes as predictors, alongside animal- and feed-related predictors using four statistical/machine learning (ML) methods. These include random forest combined with boosting (RF-B), least absolute shrinkage and selection operator (LASSO), generalized linear mixed model with LASSO (glmmLasso), and smoothly clipped absolute deviation (SCAD) implemented on linear mixed models. With a sheep dataset (218 observations) of both animal data and rumen microbiota data (relative sequence abundance of 330 genera of rumen bacteria, archaea, protozoa, and fungi), we developed linear mixed models to predict CH4 production (g CH4/animal·d, ANIM-B models) and CH4 yield (g CH4/kg of dry matter intake, DMI-B models). We also developed models solely based on animal-related data. Prediction performance was evaluated 200 times with random data splits, while fitting performance was assessed without data splitting. The inclusion of microbial predictors improved the models, as indicated by decreased root mean square prediction error (RMSPE) and mean absolute error (MAE), and increased Lin's concordance correlation coefficient (CCC). Both glmmLasso and SCAD reduced the Akaike information criterion (AIC) and Bayesian information criterion (BIC) for both the ANIM-B and the DMI-B models, while the other two ML methods had mixed outcomes. By balancing prediction performance and fitting performance, we obtained one ANIM-B model (containing 10 genera of bacteria and 3 animal data) fitted using glmmLasso and one DMI-B model (5 genera of bacteria and 1 animal datum) fitted using SCAD. This study highlights the importance of incorporating rumen microbiota data in CH4 prediction models to enhance accuracy and robustness. Additionally, ML methods facilitate the selection of microbial predictors from high-dimensional metataxonomic data of the rumen microbiota without overfitting. Moreover, the identified microbial predictors can serve as biomarkers of CH4 emissions from sheep, providing valuable insights for future research and mitigation strategies.
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Metano , Rumen , Ovinos , Animales , Femenino , Teorema de Bayes , Rumiantes , Dieta/veterinaria , Bacterias/genética , Alimentación Animal/análisis , LactanciaRESUMEN
Sieve analysis is used in feed analysis, and studies of digestive physiology with various approaches to describe an average value of particle size which can serve to compare different samples. To demonstrate the effects of such different approaches, we compared five particle size indicators to demonstrate advantages and disadvantages of each method, the modulus of fineness (MOF), the discrete mean (dMEAN) and median (dMED), and the continuous mean (cMEAN) and median (cMED), well aware of the fact that a gold standard for this procedure is lacking. Data were obtained from 580 individual faecal samples of different herbivore species by wet sieving over a cascade of nine sieves with mesh sizes ranging from 0.063 to 16 mm. MOF, dMEAN and dMED can be calculated directly from the results of sieve analysis, but cMEAN and cMED require a curve-fitting procedure. Across the whole sample size, dMEAN and cMEAN showed the highest correlation. The correlation between the respective MEAN and MED was higher for d than for c. As expected, MOF deviated most from the other measurements. Simulating different sieve sets resulted in a poor correlation between the results from the different sets in MOF and cMED, but a good correlation in dMEAN and cMEAN, suggesting that these latter measures can also be compared between studies that do not use identical sieve sets. As the calculation of dMEAN is comparatively simpler and less time-consuming than that of cMEAN, we propose the dMEAN as a standard for the description of a mean particle size value obtained from sieve analysis. For practical application, the good correlation of different simulated sieve sets indicates that sets with fewer sieves could be used in large-scale studies to reduce analytical workload.
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Manipulación de Alimentos , Contenido Digestivo , Tamaño de la Partícula , Alimentación Animal , Fenómenos Fisiológicos Nutricionales de los Animales , Animales , Heces/química , Herbivoria , Masticación , Modelos Teóricos , Especificidad de la EspecieRESUMEN
The relevance of the mean retention time (MRT) of particles through the gastrointestinal tract (GIT) is well understood and MRT(particle)GIT is an important parameter in digestion models. Solute markers have been used to estimate MRT(solute)GIT (or 'fluid passage') in animals, but the relevance of this measure is less evident and is usually sought in its relation to MRT(particle)GIT. The ratio between the two measures indicates the degree of 'digesta washing', with little washing occurring at ratios of 1, aborad washing at ratios >1 (where the solute marker travels faster than the particle marker), and orad (retrograde) washing at ratios <1 (where the solute marker travels slower than the particle marker). We analysed digesta washing in a dataset of 98 mammalian species including man of different digestion types (caecum, colon and nonruminant foregut fermenters, and ruminants), controlling for phylogeny; a subset of 72 species allowed testing for the influence of food intake level. The results indicate that MRT(solute)GIT and the degree of digesta washing are related to digestion type, whereas variation in MRT(particle)GIT is influenced mainly by effects of body mass and food intake. Thus, fluid throughput and digesta washing emerge as important correlates of digestive anatomy. Most importantly, primates appear constrained to little digesta washing compared to non-primate mammalian herbivores, regardless of their digestion type. These results may help explain the absence of primates from certain herbivore niches and represent a drastic example of a physiologic limitation in a phylogenetic group. More experimental research is required to illuminate relative benefits and costs of digesta washing.
Asunto(s)
Fenómenos Fisiológicos Nutricionales de los Animales , Tránsito Gastrointestinal , Mamíferos/fisiología , Animales , Dieta , Sistema Digestivo , Humanos , Mamíferos/clasificación , FilogeniaRESUMEN
The aim of this study was to develop a basic model to predict enteric methane emission from dairy cows and to update operational calculations for the national inventory in Norway. Development of basic models utilized information that is available only from feeding experiments. Basic models were developed using a database with 63 treatment means from 19 studies and were evaluated against an external database (n = 36, from 10 studies) along with other extant models. In total, the basic model database included 99 treatment means from 29 studies with records for enteric CH4 production (MJ/day), dry matter intake (DMI) and dietary nutrient composition. When evaluated by low root mean square prediction errors and high concordance correlation coefficients, the developed basic models that included DMI, dietary concentrations of fatty acids and neutral detergent fiber performed slightly better in predicting CH4 emissions than extant models. In order to propose country-specific values for the CH4 conversion factor Ym (% of gross energy intake partitioned into CH4) and thus to be able to carry out the national inventory for Norway, the existing operational model was updated for the prediction of Ym over a wide range of feeding situations. A simulated operational database containing CH4 production (predicted by the basic model), feed intake and composition, Ym and gross energy intake (GEI), in addition to the predictor variables energy corrected milk yield and dietary concentrate share were used to develop an operational model. Input values of Ym were updated based on the results from the basic models. The predicted Ym ranged from 6.22 to 6.72%. In conclusion, the prediction accuracy of CH4 production from dairy cows was improved with the help of newly published data, which enabled an update of the operational model for calculating the national inventory of CH4 in Norway.
RESUMEN
The present study evaluated the effects of linseed supplementation on CH4 emission and milk fatty acid composition in dairy cows measured at the group level in an experimental dairy loose housing using a tracer gas technique and individually in tied stalls and respiration chambers. Cows (2 × 20) were maintained in two separate sections under loose-housing conditions and received a diet supplemented with extruded linseed (L) lipids (29 g·kg-1 dry matter) or a control (C) diet containing corn flour. Subsequently, 2 × 6 cows per dietary group were investigated in a tied-housing system and respiration chambers. Substantially higher proportions of favorable milk fatty acids were recovered in L cows when compared with C cows at the group level, making the analysis of bulk milk a suitable control instrument for retailers. Linseed supplementation resulted in a slightly lower diurnal course of CH4 emission intensity than the control at the group and individual levels. However, we found no more than a trend for a CH4 mitigating effect, unlike in other studies supplementing similar linseed lipid levels. Feed supplements in concentrations that lead to a significant reduction in CH4 emissions must show whether the reduction potential determined at the group and individual levels is comparable.
RESUMEN
The digestion of plant material in mammalian herbivores basically depends on the chemical and structural composition of the diet, the mean particle size to which the forage is processed, and the ingesta retention time. These different factors can be influenced by the animal, and they can presumably compensate for each other. The pygmy hippopotamus, a non-ruminating foregut fermenter, has longer mean retention times than ruminants; however hippos do not achieve higher (fibre) digestibilities on comparable diets, which could be due to ineffective mastication. We performed feeding trials with six pygmy hippos (Hexaprotodon liberiensis) and six banteng cattle (Bos javanicus) on a grass diet. As predicted, both species achieved similar dry matter, organic matter, crude protein and gross energy digestibilities. However, neutral and acid detergent fibre digestibility was lower in pygmy hippos. Apparently, in these species, fibre digestibility was more influenced by particle size, which was larger in pygmy hippos compared to banteng, than by retention time. In spite of their higher relative food intake, the banteng in this study did not have greater relative gut fills than the hippos. Ruminants traditionally appear intake-limited when compared to equids, because feed particles above a certain size cannot leave the rumen. But when compared to nonruminating foregut fermenters, rumination seems to free foregut fermenters from an intrinsic food intake limitation. The higher energy intakes and metabolic rates in wild cattle compared to hippos could have life-history consequences, such as a higher relative reproductive rate.
Asunto(s)
Artiodáctilos/fisiología , Digestión/fisiología , Ingestión de Alimentos/fisiología , Tracto Gastrointestinal/anatomía & histología , Masticación/fisiología , Alimentación Animal , Animales , Animales de Zoológico , Bovinos , Tracto Gastrointestinal/fisiología , Valor Predictivo de las Pruebas , Reproducibilidad de los Resultados , Especificidad de la EspecieRESUMEN
Hazel leaves (Corylus avellana) fed to sheep resulted in decreased methane emissions without negatively affecting feed intake and were found to have antioxidant properties in vitro. The objective of this study was to evaluate effects of hazel leaves, rich in tannins, on blood antioxidant activity, cellular immune response, and heart beat parameters in sheep. Four experimental pellets were produced by mixing alfalfa and hazel leaves in different proportions, including alfalfa alone as a control, 30% and 60% of hazel leaves, the latter also with 3.8% polyethylene glycol (PEG). Six adult, nonpregnant, nonlactating female sheep (71 ± 5.7 kg of body weight) were allocated to 4 treatments in a 6 × 4 crossover design with four 18-d periods. The diet consisted of experimental pellets and ryegrass-dominated hay (ratio 80% to 20% in dry matter), resulting in hazel leaf proportions of approximately 0%, 25%, and 50% in the total diet. Blood samples were collected at the end of each period to determine plasma total phenol concentration and markers of oxidative status as well as peripheral blood mononuclear cells (PBMC) activation and proliferation response in vitro. Heart rate (HR) and HR variability parameters were measured for 2 consecutive days in each period, during different activities (i.e., eating pellets or hay, or lying). Treatments were compared with multiple comparisons and contrast analysis was used to test for linear and quadratic relations. Compared with control, feeding a high dosage of hazel leaves enhanced (P = 0.006) the plasma total antioxidant capacity, which linearly (P = 0.016) increased with increasing level of hazel leaves in the diet. The total phenol concentration and activities of the antioxidant enzymes superoxide dismutase, catalase, and glutathione reductase in the plasma were not different (P ≥ 0.23) among the treatments; however, the latter slightly increased linearly (P = 0.047) with increasing hazel leaves proportion. No differences were observed in the activation and proliferation of PBMC among treatments. The HR decreased linearly (P ≤ 0.009) during pellet eating and lying and the root mean square of successive differences of interbeat intervals (RMSSD) increased linearly (P = 0.037) when lying with increasing level of hazel leaves in the diet. In conclusion, our findings indicate that hazel leaves are a promising supplement to improve oxidative status with no effect on cellular immune response and cardiac stress level of sheep.