Review: Comparative methane production in mammalian herbivores.

Methane (CH4) production is a ubiquitous, apparently unavoidable side effect of fermentative fibre digestion by symbiotic microbiota in mammalian herbivores. Here, a data compilation is presented of in vivo CH4 measurements in individuals of 37 mammalian herbivore species fed forage-only diets, from the literature and from hitherto unpublished measurements. In contrast to previous claims, absolute CH4 emissions scaled linearly to DM intake, and CH4 yields (per DM or gross energy intake) did not vary significantly with body mass. CH4 physiology hence cannot be construed to represent an intrinsic ruminant or herbivore body size limitation. The dataset does not support traditional dichotomies of CH4 emission intensity between ruminants and nonruminants, or between foregut and hindgut fermenters. Several rodent hindgut fermenters and nonruminant foregut fermenters emit CH4 of a magnitude as high as ruminants of similar size, intake level, digesta retention or gut capacity. By contrast, equids, macropods (kangaroos) and rabbits produce few CH4 and have low CH4 : CO2 ratios for their size, intake level, digesta retention or gut capacity, ruling out these factors as explanation for interspecific variation. These findings lead to the conclusion that still unidentified host-specific factors other than digesta retention characteristics, or the presence of rumination or a foregut, influence CH4 production. Measurements of CH4 yield per digested fibre indicate that the amount of CH4 produced during fibre digestion varies not only across but also within species, possibly pointing towards variation in microbiota functionality. Recent findings on the genetic control of microbiome composition, including methanogens, raise the question about the benefits methanogens provide for many (but apparently not to the same extent for all) species, which possibly prevented the evolution of the hosting of low-methanogenic microbiota across mammals.

Accuracy of methane emissions predicted from milk mid-infrared spectra and measured by laser methane detectors in Brown Swiss dairy cows.

Since heritability of CH4 emissions in ruminants was demonstrated, various attempts to generate large individual animal CH4 data sets have been initiated. Predicting individual CH4 emissions based on equations using milk mid-infrared (MIR) spectra is currently considered promising as a low-cost proxy. However, the CH4 emission predicted by MIR in individuals still has to be confirmed by measurements. In addition, it remains unclear how low CH4 emitting cows differ in intake, digestion, and efficiency from high CH4 emitters. In the current study, putatively low and putatively high CH4 emitting Brown Swiss cows were selected from the entire Swiss herdbook population (176,611 cows), using an MIR-based prediction equation. Eventually, 15 low and 15 high CH4 emitters from 29 different farms were chosen for a respiration chamber (RC) experiment in which all cows were fed the same forage-based diet. Several traits related to intake, digestion, and efficiency were quantified over 8 d, and CH4 emission was measured in 4 open circuit RC. Daily CH4 emissions were also estimated using data from 2 laser CH4 detectors (LMD). The MIR-predicted CH4 production (g/d) was quite constant in low and high emission categories, in individuals across sites (home farm, experimental station), and within equations (first available and refined versions). The variation of the MIR-predicted values was substantially lower using the refined equation. However, the predicted low and high emitting cows (n = 28) did not differ on average in daily CH4 emissions measured either with RC or estimated using LMD, and no correlation was found between CH4 predictions (MIR) and CH4 emissions measured in RC. When individuals were recategorized based on CH4 yield measured in RC, differences between categories of 10 low and 10 high CH4 emitters were about 20%. Low CH4 emitting cows had a higher feed intake, milk yield, and residual feed intake, but they differed only weakly in eating pattern and digesta mean retention times. Low CH4 emitters were characterized by lower acetate and higher propionate proportions of total ruminal volatile fatty acids. We concluded that the current MIR-based CH4 predictions are not accurate enough to be implemented in breeding programs for cows fed forage-based diets. In addition, low CH4 emitting cows have to be characterized in more detail using mechanistic studies to clarify in more detail the properties that explain the functional differences found in comparison with other cows.

Transfer of total phenols from a grapeseed-supplemented diet to dairy sheep and goat milk, and effects on performance and milk quality.

Polyphenols are known to affect digestion of ruminants, whereas there is little information about their metabolic effects. In a 2 × 2-factorial experiment the effects of supplementing a phenolic grapeseed extract were compared in 11 East Friesian dairy sheep and 9 Saanen goats. The concentrate supplemented with 7.4 g/100 g DM grapeseed extract had contents of 3.5 g additional phenols/100 g DM and was compared with a low phenolic control concentrate. Performance, total phenols in blood, milk, urine and feces, antioxidant capacity of the blood, and saliva properties were examined. The experiment lasted for 11 wk from parturition to late lactation, with an initial adaptation phase of 1 wk. Milk yield was measured daily after weaning at about 7 wk after parturition. Blood, milk, saliva, feces and urine were sampled 4, 3, 2, 2 and 2 times per animal, respectively. The phenolic diet increased phenol concentrations in blood (+10% and 17% in wk 5 and wk 11, respectively) and in milk (+32% in wk 5) on some of the sampling weeks. There were no clear species differences in phenol concentrations in blood plasma, milk, urine and feces. However, at the end of the experiment the supplemented goats had a higher (48%) urinary phenol concentrations than the non-supplemented goats. A weak relationship (P < 0.05) was found between phenol intake and phenol excretion with milk for sheep but not goats. The phenolic diet did not influence blood antioxidant capacity and tannin binding capacity of the saliva. The saliva of the goats had a higher tannin binding capacity than sheep saliva. The effects of the extract on milk yield were inconsistent between sheep and goats. In general, goats had higher feed and nutrient intakes, were heavier, and yielded more milk. Additionally, milk protein and lactose contents were lower and milk urea content was higher in goats than sheep. In conclusion, supplementing grapeseed extract to sheep and goats elevated phenol concentrations in milk and blood to a certain extent, but most of the phenols were lost via urine. The study gave another indication that goats seem to have developed coping mechanisms like a higher salivary tannin binding capacity, mechanisms which are less pronounced in sheep.

Diet changes alter paternally inherited epigenetic pattern in male Wild guinea pigs.

Epigenetic modifications, of which DNA methylation is the most stable, are a mechanism conveying environmental information to subsequent generations via parental germ lines. The paternal contribution to adaptive processes in the offspring might be crucial, but has been widely neglected in comparison to the maternal one. To address the paternal impact on the offspring's adaptability to changes in diet composition, we investigated if low protein diet (LPD) in F0 males caused epigenetic alterations in their subsequently sired sons. We therefore fed F0 male Wild guinea pigs with a diet lowered in protein content (LPD) and investigated DNA methylation in sons sired before and after their father's LPD treatment in both, liver and testis tissues. Our results point to a 'heritable epigenetic response' of the sons to the fathers' dietary change. Because we detected methylation changes also in the testis tissue, they are likely to be transmitted to the F2 generation. Gene-network analyses of differentially methylated genes in liver identified main metabolic pathways indicating a metabolic reprogramming ('metabolic shift'). Epigenetic mechanisms, allowing an immediate and inherited adaptation may thus be important for the survival of species in the context of a persistently changing environment, such as climate change.

[Management of an elderly patient in the emergency room at the end of life : A medical ethics challenge]. / Management eines älteren Patienten in der Notaufnahme am Lebensende : Eine medizinethische Herausforderung.

A 94-year-old patient with cardiogenic shock due to myocardial infarction was admitted via the emergency room. A coronary angiography and intensive care were requested. The need for care due to dementia was known. After case discussion in the interdisciplinary and multiprofessional treatment team, the decision for a palliative care concept in the form of symptom control was made in the emergency room, taking into account the patient's medical history, the current situation, and the presumed patient consent. The integration of medical ethics aspects and palliative medicine into "geriatric emergency medicine" will present a challenge in the future.

Kinetics of solutes and particles of different size in the digestive tract of cattle of 0.5-10 years of age, and relationships with methane production.

The digestive physiology of cattle is characterised by comparatively long digesta mean retention times (MRTs), a particle sorting mechanism (difference in MRTs of large vs. small particles) and a distinct digesta washing (difference in MRTs between particles and fluids) in the reticulorumen (RR). How these processes mature during ontogeny, and how they link to other digestion characteristics and methane production, is largely unknown. We used a set of passage markers (Co-EDTA for fluids and hay particles of 2, 5 and 8 mm length mordanted with Cr, La and Ce, respectively) to measure MRTs in 12 heifers (0.5-2.1 years; hay only) and two groups of 15 lactating cows (2.4-10.0 years; forage-only vs. forage-concentrate diet). The MRTs differed between markers (Co < Cr < La < Ce) and were longer in heifers than cows, consistent with the lower feed intake in heifers. MRTs were mostly similar between cow groups and increased with age. Digesta washing was not affected by group, age, feed intake and number of chews per unit of feed. The degree of digesta washing was not related to CH4 measures. Particle sorting was more prominent in cows than heifers but did not differ between cow groups or change with age in cows. This could be the consequence of the abrupt increase in intake from heifers to cows at a time when gut capacity is not yet fully developed; particle sorting might then clear smaller particles from the RR sooner allowing a higher intake. Surprisingly, CH4 yield per ingested feed did not correlate with MRTs, and CH4 yield per unit of digested fibre decreased with increasing MRTs and with increasing fibre digestibility. As this pattern occurred in heifers and both cow groups, it appeared independent of age, indicating a mechanism that has not been described in the literature so far and requires further investigation.

Comparative selective retention of particle size classes in the gastrointestinal tract of ponies and goats.

There is a discrepancy in the literature on potential digesta separation mechanisms in horses, with both a selective retention of fine and of large particles postulated in different publications. To assess the net effect of such mechanisms, we fed ponies on a hay-only diet a pulse dose of whole (unchopped) marked hay together with a solute marker, collected faeces on a regular basis, measured marker concentrations in whole faeces and in their large (2.0-16 mm), medium (0.5-1.0 mm) and small (0.063-0.25 mm) particle fraction, and calculated the corresponding mean retention times (MRTs). For comparison, the same experiment was performed in goats. In goats, as expected, MRTsolute (35 hr) was significantly shorter than MRTparticle (51 hr); only a very small fraction of particle marker was excreted as large particles (2%); and the MRT of these large particles was significantly shorter than that of small particles (with a relevant difference of 8.6 hr), indicating that those few large particles that escape the rumen do so mostly soon after ingestion. In ponies, MRTsolute (24 hr) did not differ from MRTparticle (24 hr); a higher fraction of particle marker was excreted as large particles (5%); and the MRT of these large particles was longer than that of small particles (but with a non-relevant difference of less than 1 hr). These results indicate that no relevant net separation of digesta phases occurs in horses and that selective particle retention mechanisms in the large intestine are unlikely to represent important characteristics of the horse's digestive physiology.

Assessment of anti-inflammatory properties of extracts from Honeysuckle (Lonicera sp. L., Caprifoliaceae) by ATR-FTIR spectroscopy.

Inflammation is a hallmark of some of today's most life-threatening diseases such as arteriosclerosis, cancer, diabetes and Alzheimer's disease. Herbal medicines (HMs) are re-emerging resources in the fight against these conditions and for many of them, anti-inflammatory activity has been demonstrated. However, several aspects of HMs such as their multi-component character, natural variability and pharmacodynamic interactions (e.g. synergism) hamper identification of their bioactive constituents and thus the development of appropriate quality control (QC) workflows. In this study, we investigated the potential use of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy as a tool to rapidly and non-destructively assess different anti-inflammatory properties of ethanolic extracts from various species of the Genus Lonicera (Caprifoliaceae). Reference measurements for multivariate calibration comprised in vitro bioactivity of crude extracts towards four key players of inflammation: Nitric oxide (NO), interleukin 8 (IL-8), peroxisome proliferator-activated receptor ß/δ (PPAR ß/δ), and nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB). Multivariate analysis of variance (MANOVA) revealed a statistically significant, quantitative pattern-activity relationship between the extracts' ATR-FTIR spectra and their ability to modulate these targets in the corresponding cell models. Ensemble orthogonal partial least squares (OPLS) discriminant models were established for the identification of extracts exhibiting high and low activity with respect to their potential to suppress NO and IL-8 production. Predictions made on an independent test set revealed good generalizability of the models with overall sensitivity and specificity of 80% and 100%, respectively. Partial least squares (PLS) regression models were successfully established to predict the extracts' ability to suppress NO production and NF-κB activity with root mean squared errors of cross-validation (RMSECV) of 8.7% and 0.05-fold activity, respectively.

Cryopreservation of captive roe deer (Capreolus capreolus) semen.

To address the need to preserve current genetic diversity before it is lost forever; further studies to adapt assisted reproductive technologies to various endangered species are needed, among other things. Roe deer (Capreolus capreolus), an over abundant wild deer, can serve as model species to develop or improve sperm cryopreservation of threatened or endangered deer species. The aim of this study was to compare the ability of three diluents (Berliner Cryomedium [BC]; Tris, citric acid, glucose [TCG]; TES, Tris, glucose) to support chilling, cryopreservation (with 5% glycerol; G) and postthaw incubation (at 22 °C and 37 °C) of roe deer spermatozoa collected by electroejaculation. Berliner Cryomedium was the diluent that better preserved roe deer spermatozoa during refrigeration, able to maintain motility for at least 14 days, longer than the other extenders. BC + G was the extender of choice for cryopreservation, showing higher viability compared with TCG + G (66.7 ± 3.4 vs. 54.5 ± 6.5; P < 0.05) and higher level of acrosome integrity compared with TES, Tris, glucose + G (79.4 ± 3.4 vs. 67.9 ± 5.0; P < 0.05). Maintaining the samples at 22 °C after thawing presented higher values in various parameters compared with 37 °C. The knowledge gained through this study can potentially act as a preliminary step toward development of new protocols to help increase the reproductive success of biologically similar, yet endangered, wild species.

Biological implications of longevity in dairy cows: 1. Changes in feed intake, feeding behavior, and digestion with age.

Milk production strategies focusing on longevity and limited use of concentrate are receiving increasing attention. To evaluate such strategies, knowledge of the development with age of animal characteristics, particularly digestion, is indispensable. We therefore investigated the development of feed intake, chewing activity, and digestion in 30 lactating Brown Swiss cows (876-3,648 d old) and 12 heifers (199-778 d old). We also studied whether age effects were exhibited differently in animals selected from herds subjected for 11 yr either to a forage-only or to a forage-concentrate feeding regimen. Forages consisted of grass hay (the only feed for heifers), corn silage, and grass pellets. Measurements lasted for 8 d, where amounts and composition of feeds, feces, and milk were recorded and analyzed. Ruminal pH data and eating and rumination activity were assessed by pH sensors put into the rumen and halter-mounted noseband sensors. The mean retention time of feed particles was assessed using Cr-mordanted fiber and data were used to calculate dry matter gut fill. Data were subjected to regression analyses with age and feeding regimen as explanatory variables, and body weight, milk yield, and proportion of hay in forage as covariates. This allowed separating age-related changes of body weight and milk yield from independent age effects and correcting for differences in preference for individual forages. In cows, organic matter intake increased with age (from slightly below to above 20kg/d), as did mean retention time and gut fill. Digestibility of organic matter did not show a clear age dependency, but fiber digestibility had a maximum in cows of around 4 to 6 yr of age. Ruminal pH and absolute eating and rumination times did not vary with cow age. Young and old cows chewed regurgitated boluses more intensively (60-70 times) than middle-aged cows (about 50 times). Effects of feeding regimen were small, except for fiber intake and rumination time per unit of intake, owing to the different fiber content of the diets. No significant interactions between age and feeding regimen were found. Heifers spent more time eating and ruminating per unit of feed than cows, which resulted in a high fiber digestibility. Irrespective of the feeding regimen tested, older cows maintained intake and digestion efficiency with longer retention times and chewing rumination boluses more intensively. The results support efforts to extend the length of productive life in dairy cows.

Retention of solute and particle markers in the digestive tract of chinchillas (Chinchilla laniger).

The chinchilla (Chinchilla laniger) is a herbivorous hystricomorph South American rodent for which no mean digesta retention times have been reported so far. Six animals (mean body mass ± standard deviation: 513 ± 99 g) on a diet of grass hay and lucerne-based pellets were given a pulse dose of a solute (cobalt-EDTA) and a particle (chromium-mordanted fibre, <2 mm) marker with subsequent frequent faecal collection. Dry matter intake was 45.2 ± 8.0 g/kg(0.75) /day. Mean retention times were 22.2 ± 5.3 h for solutes and 25.4 ± 5.2 h for particles, with the difference being not significant within individuals. This indicates the presence of a 'mucus-trap' colonic separation mechanism, which is in accord with morphological descriptions of the typical colonic furrow in chinchillas. Corresponding to a strategy of colonic digesta separation and caecotroph formation, secondary marker excretion peaks indicated coprophagic events that were spaced approximately 12 h apart. Given that these retention times appear longer than measures reported for rabbits (Oryctolagus cuniculus) or guinea pigs (Cavia procellus), it would be interesting to compare the digestive efficiency of chinchillas on high levels of dietary fibre to other species.

Digestive physiology, metabolism and methane production of captive Linné's two-toed sloths (Choloepus didactylus).

Sloths are renowned for their low metabolic rate, low food intake and low defecation frequency. We investigated factors of digestive physiology and energy metabolism in four captive individuals (mean body mass 10.0 ± SD 3.7 kg) of a hitherto mostly unstudied sloth species, Linné's two-toed sloth (Choloepus didactylus), in a 2-week digestion recording and 23-h respiration experiment on animals fed a standard zoo diet of vegetables and starchy components. Dry matter intake, defecation frequency and particle mean retention time (MRT) in the gastrointestinal tract (GIT) were 12 ± 3 g/(kg(0.75)  day), once every 5 days and >140 h in three individuals, but 53 g/(kg(0.75)  day), daily and 82 h in one individual that was apparently compensating for a period of weight loss prior to the experiment. In all animals, solute marker was eliminated at a faster rate than the particle marker, indicating 'digesta washing' in the sloths' GIT. The overall metabolic rate calculated from oxygen consumption matched the metabolisable energy intake in three individuals [173 ± 22 vs. 168 ± 44 kJ/(kg(0.75)  day)] but not in the fourth one [225 vs. 698 kJ/(kg(0.75)  day)], supporting the interpretation that this animal was replenishing body stores. In spite of the low food intake and the low-fibre diet (209 ± 26 g neutral detergent fibre/kg dry matter), methane production was rather high accounting for 9.4 ± 0.8% of gross energy intake (2.7% in the fourth individual), which exceeded literature data for ruminants on forage-only diets. These results corroborate literature reports on low intake, low defecation frequency, low metabolic rate and long MRT in other sloth species. The long MRT is probably responsible for the comparatively high methane production, providing more opportunity for methanogenic archaea than in other non-ruminant mammals to produce significant amounts of methane.

Digestive physiology of captive giant anteaters (Myrmecophaga tridactyla): determinants of faecal dry matter content.

Giant anteaters (Myrmecophaga tridactyla) are specialized insectivores and consume mainly ants and termites in the wild. In captivity, giant anteaters are either fed a complete diet, or a combination of a domestic carnivore diet with leaf eater pellets, or a traditional gruel-type diet. Soft faeces are a frequently encountered problem with this type of feeding. In the present study, we analysed diet and faeces composition, calculated digestibility and measured mean retention time on various diets in eight giant anteaters (total of n = 64 experiments). The results suggest that the digestive physiology of giant anteaters is similar to that of domestic dogs and cats in terms of nutrient digestibility and digesta retention. When testing correlations between faecal dry matter content and other variables, no relationship with dietary crude fibre content or mean digesta retention time could be detected. However, acid insoluble ash intake was significantly and positively correlated with faecal dry matter content. The amount of acid insoluble ash excreted with the faeces was higher than that ingested with the diet offered, indicating that the giant anteaters ingested soil from their enclosure of up to 93 g per day. This finding is consistent with observation of faeces of wild giant anteaters that contain soil or sand most likely due to indiscriminate feeding. It also corresponds to reports that indigestible materials such as peat, soil, chitin or cellulose contribute to a firmer faecal consistency in various carnivore species. Therefore, offering giant anteaters the opportunity to voluntarily ingest soil from their enclosure might be beneficial.

The effect of very low food intake on digestive physiology and forage digestibility in horses.

Equid digestion is often conceptualized as a high-throughput/low-efficiency system, in particular compared with ruminants. It is commonly assumed that ruminants have an advantage when resources are limited; the effect of low food intake on digestive physiology of horses has, however, not been explored to our knowledge. We used four adult ponies [initial body mass (BM) 288 ± 65 kg] in two subsequent trials with grass hay-only diets [in dry matter (DM): hay1, mid-early cut, crude protein (CP) 10.5%, neutral detergent fibre (NDF) 67.6%; hay2, late cut, CP 5.8%, NDF 69.5%], each fed subsequently at four different dry matter intake (DMI) levels: ad libitum and at 75, 55 and 30 g/kg(0.75) /day. We particularly expected digesta mean retention times (MRT) to increase, and hence fibre digestibility to increase, with decreasing DMI. Ponies maintained BM on the first, but lost BM and body condition on DMI55 and DMI30. MRTs were negatively correlated to DMI and ranged (for particles <2 mm) from 23/31 h (hay1/2) on the ad libitum to 38/48 h on DMI30. Digestibilities of DM, nutrients and fibre components decreased from DMI75 to DMI30; apparent digestibilities of organic matter and NDF (hay1/2) dropped from 47/43% and 42/37%, respectively, on the ad libitum DMI to 35/35% and 30/28% on DMI30. Additional differences evident between the two hays included a higher estimated 'true' protein digestibility for hay1 and finer faecal particles on hay2; there were no differences in faecal particle size between intake levels. The results suggest that below a certain food intake threshold, the major digestive constraint is not fermentation time but nutrient supply to gut bacteria. The threshold for such an effect probably varies between feeds and might differ between ruminants and equids.

Influence of diet and stress on reproductive hormones in Nigerian olive baboons.

A female mammal's reproductive function and output are limited by the energy she is able to extract from her environment. Previous studies of the interrelationships between energetic circumstances and reproductive function in a variety of mammal species have produced varied results, which do not all support the common assumption that higher female reproductive hormone levels, specifically progesterone, indicate better ovarian function and greater reproductive potential, and are associated with lower energetic stress. In the present study faecal progesterone and glucocorticoid levels were assessed in two troops of olive baboons (Papio anubis) in the same population. They face similar ecological challenges, except that one troop crop-raids, potentially affecting its energetic intake and stress levels. The energy intake of individual females was assessed by combining detailed feeding observations with nutritional analysis of food samples. The crop-raiding troop experienced 50% higher energy intake rates and 50% lower glucocorticoid levels compared to the non-crop-raiding troop alongside substantially lower progesterone levels. This suggests that energetic stress is associated with elevated progesterone levels and may be the cause of the non-crop-raiding troop's lower reproductive output. By comparing groups which differ little, except in terms of food access, and also by directly assessing energy intake, our study addresses some of the design limitations of previous research investigating variation in progesterone levels and energetic stress. It therefore has the potential to contribute to greater understanding of the factors affecting differences in reproductive and stress hormone levels and reproductive function in mammals experiencing different energetic circumstances.

Energy intake for maintenance in a mammal with a low basal metabolism, the giant anteater (Myrmecophaga tridactyla).

Giant anteaters (Myrmecophaga tridactyla) are among those mammals for which a particularly low metabolism has been reported. In order to verify presumably low requirements for energy, we used eight anteaters (two males, six females; aged 1-14 years; body mass between 46 and 64 kg) in a total of 64 individual trials, in which a variety of intake levels was achieved on various diets. Digestible energy (DE) intake was quantified by measuring food intake and faecal excretion and analysing representative samples for gross energy, and animals were weighed regularly. Maintenance DE requirements were calculated by regression analysis for the DE intake that corresponded to zero weight change. Differences between individuals were significant. Older anteaters (n = 3 animals aged 12-15 years in 29 trials) had lower relative requirements than younger ones (n = 5 animals aged 1-7 years in 35 trials); thus, giant anteaters resemble other mammals in which similar age-specific differences in energy requirements are known. However, estimated maintenance requirements were 347 kJ DE/kg(0.75)/day in the anteaters, which is low compared to the 460-580 kJ DE/kg(0.75)/day maintenance requirements of domestic dogs. The lack of knowledge that metabolic requirements are below the mammalian average could make species particularly susceptible to overfeeding, if amounts considered adequate for average mammals were provided. Non-scientific reports on comparatively fast growth rates and high body masses in captive giant anteaters as compared to free-ranging animals suggest that body mass development and feeding regimes in captivity should be further assessed.

Physical characteristics of reticuloruminal contents of oxen in relation to forage type and time after feeding.

The stratification of reticulorumen (RR) contents has been described in domestic ruminants, but suspected to be absent in certain wild ruminant species. To investigate how such stratification could be quantified, we tested variables indicating stratification in three oxen with rumen cannulae, fed once daily for 3 h, one of three different forages (fresh grass FG, grass hay GH, lucerne hay LH). Ingesta samples from dorsal rumen (DR), ventral rumen (VR) and reticulum (RET) were taken at 0, 3, 6, 12 and 24 h after the last meal and analyzed for dry matter (DM) concentration, mean particle size and proportion of floating/sedimenting particles. Viscosity was measured in centrifuged RR fluid. There was no relevant variation in rumen fluid viscosity over time or with feeding regime. Dry matter content in DR was always higher than in VR or RET and increased after feeding. When LH and FG were fed, DR always contained larger particles than VR, except at 6 and 12 h of feeding GH. The proportion of floating particles was higher in DR than VR except at GH 6 h and GR between 6 and 12 h. The floating particle fraction mostly contained larger particles, except for GH 3 h in both DR and VR and for FG 3-12 h in DR. Changes in the distribution of particle size and proportion of floating particles over time comply with the theoretical course of fermentative digestion for different forages, but make these variables unreliable indicators of stratification in less controlled settings, such as investigations in wild ruminants. In contrast, viscosity of rumen fluids appears constant over time and feeding regime and might be used as a species-specific variable. The difference in DM content in DR and VR is a reliable indicator for RR contents stratification characterized by an oversaturation of the contents with fluid, leading to lower VR DM contents.

No easy solution for the fractionation of faecal nitrogen in captive wild herbivores: results of a pilot study.

Faecal nitrogen (FN) concentration is used as a marker for habitat quality and digestive efficiency in free-ranging herbivores. In herbivores, FN can be separated into undigested plant N (analysed as the N concentration of the neutral detergent residue) and metabolic faecal N (MFN). It has been suggested that by differential analysis of the faecal fibre-bound N, the MFN fraction can be further split into a bacterial N and an endogenous N fraction [Hesta et al., Br. J. Nutr. 90 (2003) 1007]. We applied these methods to 96 faecal samples of 48 mammalian herbivore species from zoos. Species were grouped into coprophageous and non-coprophageous hindgut fermenters and ruminating and non-ruminating foregut fermenters. Diet was not controlled. The FN decreased with body mass, possibly reflecting higher proportions of concentrates in diets of smaller animals. The proportion of MFN increased with FN, indicating that higher quality food might enhance the gastrointestinal bacterial flora. The only outlier to this pattern was the lesser panda (Ailurus fulgens), confirming the low relevance of fermentative digestion in this herbivorous 'carnivore'. No relevant differences between the four digestion types were noted. The proportion of endogenous faecal N (32-80% of FN) was always higher than that of bacterial faecal N (7-30%), which contradicts basal understanding of herbivore digestive physiology. Thus, the method of Hesta et al. (2003) does not appear applicable to herbivores. While the results do not exclude the possibility that detailed differences might occur between digestion types, they indicate a high degree of similarity between herbivores that rely on bacterial fermentation, regardless of their digestion type, with respect to metabolic faecal losses.

The influence of dietary tannin supplementation on digestive performance in captive black rhinoceros (Diceros bicornis).

Free-ranging browsers such as the black rhinoceros (Diceros bicornis) consume a diet that contains tannins, whereas the diets offered to them in captivity consist mostly of items known to contain hardly any such secondary plant compounds. Tannins could have potentially beneficial effects, including the chelation of dietary iron (iron storage disease is a common problem in black rhinos). Here, we tested the acceptance, and the consequences on digestion variables, of a low-dose tannin supplementation in captive animals. Eight black rhinoceroses from three zoological institutions were used. Faecal output was quantified by total faecal collection. Diets fed were regular zoo diets supplemented with either tannic acid (T, hydrolysable tannin) or quebracho (Q, condensed tannins); overall tannin source intake increased at 5-15 g/kg dry matter (DM) in relation to regular zoo diets. Adaptation periods to the new diets were >2 months. Additional data were taken from one hitherto unpublished study. Data were compared to measurements in the same animals on their regular zoo diets. All animals accepted the new diets without hesitation. There was no influence of tannin supplementation on digestion coefficients of DM and its constituents, or faecal concentrations of short-chain fatty acids or lactate. Water intake did not increase during tannin supplementation. Should the inclusion of dietary tannin sources be an objective in the development of diets for captive rhinoceroses, moderate doses such as used in this study are unlikely to cause relevant depressions of digestive efficiency and will not interfere with bacterial fermentation in a relevant way.

Development of diabetes in obese, insulin-resistant mice: essential role of dietary carbohydrate in beta cell destruction.

AIMS/HYPOTHESIS: The role of dietary carbohydrate in the pathogenesis of type 2 diabetes is still a subject of controversial debate. Here we analysed the effects of diets with and without carbohydrate on obesity, insulin resistance and development of beta cell failure in the obese, diabetes-prone New Zealand Obese (NZO) mouse. MATERIALS AND METHODS: NZO mice were kept on a standard diet (4% [w/w] fat, 51% carbohydrate, 19% protein), a high-fat diet (15, 47 and 17%, respectively) and a carbohydrate-free diet in which carbohydrate was exchanged for fat (68 and 20%, respectively). Body composition and blood glucose were measured over a period of 22 weeks. Glucose tolerance tests and euglycaemic-hyperinsulinaemic clamps were performed to analyse insulin sensitivity. Islet morphology was assessed by immunohistochemistry. RESULTS: Mice on carbohydrate-containing standard or high-fat diets developed severe diabetes (blood glucose >16.6 mmol/l, glucosuria) due to selective destruction of pancreatic beta cells associated with severe loss of immunoreactivity of insulin, glucose transporter 2 (GLUT2) and musculoaponeurotic fibrosarcoma oncogene homologue A (MafA). In contrast, mice on the carbohydrate-free diet remained normoglycaemic and exhibited hyperplastic islets in spite of a morbid obesity associated with severe insulin resistance and a massive accumulation of macrophages in adipose tissue. CONCLUSIONS/INTERPRETATION: These data indicate that the combination of obesity, insulin resistance and the inflammatory response of adipose tissue are insufficient to cause beta cell destruction in the absence of dietary carbohydrate.