Freezing African elephant semen as a new population management tool.

BACKGROUND: The captive elephant population is not self-sustaining and with a limited number of breeding bulls, its genetic diversity is in decline. One way to overcome this is to import young and healthy animals from the wild. We introduce here a more sustainable alternative method - importation of semen from wild bulls without removing them from their natural habitat. Due to the logistics involved, the only practical option would be to transport cryopreserved sperm. Despite some early reports on African elephant semen cryopreservation, the utility of this new population management tool has not been evaluated. METHODOLOGY/PRINCIPAL FINDINGS: Semen was collected by electroejaculation from 14 wild African savanna elephant (Loxodonta africana) bulls and cryopreserved using the directional freezing technique. Sperm treatments evaluated included the need for centrifugation, the use of hen or quail yolk, the concentration of glycerol (3%, 5% or 7%) in the extender, and maintenance of motility over time after thawing. Our results suggest that dilution in an extender containing hen yolk and 7% glycerol after centrifugation best preserved post-thaw sperm motility when compared to all other treatments (P≤0.012 for all). Using this approach we were able to achieve after thawing (mean ± SD) 54.6±3.9% motility, 85.3±2.4% acrosome integrity, and 86.8±4.6% normal morphology with no decrease in motility over 1 h incubation at 37°C. Sperm cryopreserved during this study has already lead to a pregnancy of a captive female elephant following artificial insemination. CONCLUSIONS/SIGNIFICANCE: With working techniques for artificial insemination and sperm cryopreservation of both African and Asian elephants in hand, population managers can now enrich captive or isolated wild elephant populations without removing valuable individuals from their natural habitat.

Variation in growth and potentially associated health status in Hermann's and spur-thighed tortoise (Testudo hermanni and Testudo graeca).

Captive reptiles often show higher growth rates than in the wild, possibly due to higher feeding intensity. Although health problems are usually linked to inappropriate diets, fast growth itself, such as triggered by appropriate diets fed in high amounts, has traditionally also been considered unfavorable for tortoises. We document growth rates (based on age and mass) from private Testudo hermanni and T. graeca breeders, which are generally higher than those reported for free-ranging specimens, but show enormous variation. Tortoise patients presented to an exotics clinic also covered the whole growth rate spectrum. To test whether fast growth was associated with diseases, the age-body mass relationship of these patients was tested, in a retrospective evaluation, for additional influence factors, such as dietary history and occurrence of certain diet and growth-related diseases. No indication was found that animals particularly heavy for their age were more prone to diet/growth-related disorders. In general, tortoises fed diets with meat/grain were heavier for their age than tortoises fed more appropriate diets; dietary history was not related to a particular disease. The results suggest the age-body mass relationship may not be suitable for testing effects of fast growth; an age-body length relationship would be more appropriate. Animals presented for a diet/growth-related disorder were younger than animals presented for other reasons; there was a significant negative correlation between the severity of pyramiding and age, suggesting that growth-related disorders may well limit the life expectancy of tortoises. Controlled clinical studies are required to fully test this hypothesis.

Condensing results of wet sieving analyses into a single data: a comparison of methods for particle size description.

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.

Phylogenetic constraints on digesta separation: Variation in fluid throughput in the digestive tract in mammalian herbivores.

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.

Mating system, feeding type and ex situ conservation effort determine life expectancy in captive ruminants.

Zoo animal husbandry aims at constantly improving husbandry, reproductive success and ultimately animal welfare. Nevertheless, analyses to determine factors influencing husbandry of different species are rare. The relative life expectancy (rLE; life expectancy (LE) as proportion of longevity) describes husbandry success of captive populations. Correlating rLE with biological characteristics of different species, reasons for variation in rLE can be detected. We analysed data of 166 901 animals representing 78 ruminant species kept in 850 facilities. The rLE of females correlated with the percentage of grass in a species' natural diet, suggesting that needs of species adapted to grass can be more easily accommodated than the needs of those adapted to browse. Males of monogamous species demonstrate higher rLE than polygamous males, which matches observed differences of sexual bias in LE in free-living populations and thus supports the ecological theory that the mating system influences LE. The third interesting finding was that rLE was higher in species managed by international studbooks when compared with species not managed in this way. Our method facilitates the identification of biological characteristics of species that are relevant for their husbandry success, and they also support ecological theory. Translating these findings into feeding recommendations, our approach can help to improve animal husbandry.

A longitudinal study on avian polyomavirus-specific antibodies in captive Spix's macaws (Cyanopsitta spixii).

Avian polyomavirus (APV) causes a range of disease syndromes in psittacine birds, from acute fatal disease to subclinical infections, depending on age, species, and other unidentified risk factors. To determine the prevalence of APV-specific antibodies in a captive population of Spix's macaws (Cyanopsitta spixii) in Quatar, 54 birds were tested by blocking enzyme-linked immunosorbent assay. A prevalence of 48.1% for APV antibodies, which indicates viral exposure, was found. Of 36 Spix's macaws that were serially tested over a period of 4 years, 50.0% were consistently positive, 36.1% were consistently negative, 5.5% had permanently declining antibody levels, and 2.8% showed variable results. By using polymerase chain reaction testing on whole blood samples, an apparent viremia was detected in 1 of 44 birds (2.3%), although contamination provides a likely explanation for this isolated positive result in a hand-reared chick. The white blood cell count was significantly higher in antibody-positive birds compared with antibody-negative birds (P < .05). Because antibody-positive and antibody-negative birds were housed together without a change in their respective antibody status, transmission of APV within the adult breeding population appeared to be a rare event.

To chew or not to chew: fecal particle size in herbivorous reptiles and mammals.

A major difference between reptile and mammalian herbivores is that the former do not masticate their food. Actually, food particle size reduction by chewing is usually considered one of the adaptations facilitating the higher metabolic rates of mammals. However, quantitative comparisons of ingesta particle size between the clades have, to our knowledge, not been performed so far. We measured mean fecal particle size (MPS) in 79 captive individuals of 14 reptile herbivore species (tortoises, lizards, and Corucia zebrata) by wet sieving and compared the results with a mammalian dataset. MPS increased with body mass in both clades, but at a significantly higher level in reptiles. Limited evidence in free-ranging and captive individuals of Testudo hermanni indicates that in reptiles, the ability to crop food and food particle size significantly influence fecal particle size. The opportunistic observation of a drastic particle size difference between stomach and intestinal contents corroborates findings that in reptiles, in contrast to terrestrial mammals, significant ingesta particle size reduction does occur in the gastrointestinal tract, most likely owing to microbial action during very long ingesta retention. Whether behavioral adaptations to controlling ingesta particle size, such as deliberate small bite sizes, are adaptive strategies in reptiles remains to be investigated.

Relevance of management and feeding regimens on life expectancy in captive deer.

OBJECTIVE: To establish a demographic approach to facilitate the comparison of husbandry success for deer species in zoos and to test for factors that influence the performance of deer species in captivity. SAMPLE POPULATION: Data collected from 45,736 zoo-kept deer that comprised 31 species. PROCEDURES: Data had been collected by the International Species Information System during the last 3 decades on zoo-kept deer around the world. The relative life expectancy (rLE) of a species (ie, mean life expectancy as a proportion of the maximum recorded life span for that species) was used to describe zoo populations. The rLE (values between 0 and 1) was used to reflect the husbandry success of a species. RESULTS: A significant positive correlation was found between the rLE of a species and the percentage of grass in the natural diet of the species, suggesting that there are more problems in the husbandry of browsing than of grazing species. The 4 species for which a studbook (ie, record of the lineage of wild animals bred in captivity) was maintained had a high rLE, potentially indicating the positive effect of intensive breeding management. CONCLUSION AND CLINICAL RELEVANCE: The rLE facilitated the comparison of husbandry success for various species and may offer the possibility of correlating this quotient with other biological variables. Ultimately, identifying reasons for a low husbandry success in certain species may form the basis for further improvements of animal welfare in captivity.

Passage marker excretion in red kangaroo (Macropus rufus), collared peccary (Pecari tajacu) and colobine monkeys (Colobus angolensis, C. polykomos, Trachypithecus johnii).

Ruminants are characterized by an efficient particle-sorting mechanism in the forestomach (FRST) followed by selective rechewing of large food particles. For the nonruminating foregut fermenter pygmy hippo it was demonstrated that large particles are excreted as fast as, or faster than, the small particles. The same has been suggested for other nonruminating foregut fermenters. We determined the mean retention time of fluids and different-sized particles in six red kangaroos (Macropus rufus), seven collared peccaries (Pecari tajacu) and three colobine monkeys (Colobus angolensis, C. polykomos, Trachypithecus johnii). We fed Co-EDTA as fluid and mordanted fiber as particle markers (Cr, Ce). Mean (+ or - SD) total tract retention time for fluids, small and large particles was 14 + or - 2, 29 + or - 10 and 30 + or - 9 hr in red kangaroos, 26 + or - 2, 34 + or - 5 and 32 + or - 3 hr in collared peccaries and 57 + or - 17, 55 + or - 19 and 54 + or - 19 hr in colobine monkeys, respectively. Large and small particles were excreted simultaneously in all species. There was no difference in the excretion of fluids and particles in the colobine monkeys, in contrast to the other foregut fermenters. In the nonprimate, nonruminant foregut fermenters, the difference in the excretion of fluids and small particles decreases with increasing food intake. On the contrary, ruminants keep this differential excretion constant at different intake levels. This may be a prerequisite for the sorting of particles in their FRST and enable them to achieve higher food intake rates. The functional significance of differential excretion of fluids and particles from the FRST requires further investigations.

The intraruminal papillation gradient in wild ruminants of different feeding types: Implications for rumen physiology.

Browsing and grazing ruminants are thought to differ in the degree their rumen contents are stratified-which may be due to different characteristics of their respective forages, to particular adaptations of the animals, or both. However, this stratification is difficult to measure in live animals. The papillation of the rumen has been suggested as an anatomical proxy for stratification-with even papillation indicating homogenous contents, and uneven papillation (with few and small dorsal and ventral papillae, and prominent papillae in the atrium ruminis) stratified contents. Using the surface enlargement factor (SEF, indicating how basal mucosa surface is increased by papillae) of over 55 ruminant species, we demonstrate that differences between the SEF(dorsal) or SEF(ventral) and the SEF(atrium) are significantly related to the percentage of grass in the natural diet. The more a species is adapted to grass, the more distinct this difference, with extreme grazers having unpapillated dorsal and ventral mucosa. The relative SEF(dorsal) as anatomical proxy for stratification, and the difference in particle and fluid retention in the rumen as physiological proxy for stratification, are highly correlated in species (n = 9) for which both kind of data are available. The results support the concept that the stratification of rumen contents varies among ruminants, with more homogenous contents in the more browsing and more stratified contents in the more grazing species.

More efficient mastication allows increasing intake without compromising digestibility or necessitating a larger gut: comparative feeding trials in banteng (Bos javanicus) and pygmy hippopotamus (Hexaprotodon liberiensis).

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.

Physical characteristics of rumen contents in two small ruminants of different feeding type, the mouflon (Ovis ammon musimon) and the roe deer (Capreolus capreolus).

In domestic ruminants, the stratification of forestomach contents - the results of flotation and sedimentation processes - is an important prerequisite for the selective particle retention in this organ. A series of anatomical and physiological measurements suggests that the degree of this stratification varies between browsing and grazing wild ruminants. We investigated the forestomach contents of free-ranging mouflon and roe deer shot during regular hunting procedures. There was no difference between the species in the degree by which forestomach ingesta separated according to size due to buoyancy characteristics in vitro. However, forestomach fluid of roe deer was more viscous than that of mouflon, and no difference in moisture content was evident between the dorsal and the ventral rumen in roe deer, in contrast to mouflon. Hence, the forestomach milieu in roe deer appears less favourable for gas or particle separation due to buoyancy characteristics. These findings are in accord with notable differences in forestomach papillation between the two species. In roe deer, particle separation is most likely restricted to the reticulum, whereas in mouflon, the whole rumen may pre-sort particles to a higher degree. The results suggest that differences in forestomach physiology may occur across ruminant species.

Higher masseter muscle mass in grazing than in browsing ruminants.

Using cranioskeletal measurements, several studies have generated evidence that grazing ruminants have a more pronounced mastication apparatus, in terms of muscle insertion areas and protuberances, than browsing ruminants, with the resulting hypothesis that grazers should have larger, heavier chewing muscles than browsers. However, the only investigation of this so far [Axmacher and Hofmann (J Zool 215:463-473, 1988)] did not find differences between ruminant feeding types in the masseter muscle mass of 22 species. Here, we expand the dataset to 48 ruminant species. Regardless of phylogenetic control in the statistical treatment, there was a significant positive correlation of body mass and masseter mass, and also a significant association between percent grass in the natural diet and masseter mass. The results support the concept that ruminant species that ingest more grass have relatively larger masseter muscles, possibly indicating an increased requirement to overcome the resistance of grass forage. The comparative chewing resistance of different forage classes may represent a rewarding field of ecophysiological research.

Modelling digestive constraints in non-ruminant and ruminant foregut-fermenting mammals.

It has been suggested that large foregut-fermenting marsupial herbivores, the kangaroos and their relatives, may be less constrained by food intake limitations as compared with ruminants, due mainly to differences in their digestive morphology and management of ingesta particles through the gut. In particular, as the quality of forage declines with increasing contents of plant fibre (cellulose, hemicelluloses and lignin; measured as neutral-detergent fibre, NDF), the tubiform foregut of kangaroos may allow these animals to maintain food intakes more so than ruminants like sheep, which appear to be limited by fibrous bulk filling the foregut and truncating further ingestion. Using available data on dry matter intake (DMI, g kg(-0.75) d(-1)), ingesta mean retention time (MRT, h), and apparent digestibility, we modelled digestible dry matter intake (DDMI) and digestible energy intake (DEI) by ruminant sheep (Ovis aries) and by the largest marsupial herbivore, the red kangaroo (Macropus rufus). Sheep achieved higher MRTs on similar DMIs, and hence sheep achieved higher DDMIs for any given level of DMI as compared with kangaroos. Interestingly, MRT declined in response to increasing DMI in a similar pattern for both species, and the association between DMI and plant NDF contents did not support the hypothesis that kangaroos are less affected by increasing fibre relative to sheep. However, when DEI was modelled according to DDMIs and dietary energy contents, we show that the kangaroos could meet their daily maintenance energy requirements (MER) at lower levels of DMI and on diets with higher fibre contents compared with sheep, due largely to the kangaroos' lower absolute maintenance and basal energy metabolisms compared with eutherians. These results suggest that differences in the metabolic set-point of different species can have profound effects on their nutritional niche, even when their digestive constraints are similar, as was the case for these ruminant and non-ruminant foregut fermenters.

The influence of natural diet composition, food intake level, and body size on ingesta passage in primates.

An important component of digestive physiology involves ingesta mean retention time (MRT), which describes the time available for digestion. At least three different variables have been proposed to influence MRT in herbivorous mammals: body mass, diet type, and food intake (dry matter intake, DMI). To investigate which of these parameters influences MRT in primates, we collated data for 19 species from trials where both MRT and DMI were measured in captivity, and acquired data on the composition of the natural diet from the literature. We ran comparative tests using both raw species values and phylogenetically independent contrasts. MRT was not significantly associated with body mass, but there was a significant correlation between MRT and relative DMI (rDMI, g/kg(0.75)/d). MRT was also significantly correlated with diet type indices. Thus, both rDMI and diet type were better predictors of MRT than body mass. The rDMI-MRT relationship suggests that primate digestive differentiation occurs along a continuum between an "efficiency" (low intake, long MRT, high fiber digestibility) and an "intake" (high intake, short MRT, low fiber digestibility) strategy. Whereas simple-stomached (hindgut fermenting) species can be found along the whole continuum, foregut fermenters appear limited to the "efficiency" approach.

Excretion patterns of fluid and different sized particle passage markers in banteng (Bos javanicus) and pygmy hippopotamus (Hexaprotodon liberiensis): two functionally different foregut fermenters.

Processing of ingesta particles plays a crucial role in the digestive physiology of herbivores. In the ruminant forestomach different sized particles are stratified into a small and a large particle fraction and only the latter is regurgitated and remasticated to smaller, easier-to-digest particles. In contrast, it has been suggested that in non-ruminating foregut fermenters, such as hippopotamuses, larger particles should be selectively excreted since they tend to be digested at a slower rate and hence can be considered intake-limiting bulk. In our study we determined the mean retention time (MRT) of fluids and different sized particles (2 mm and 10 mm) in six pygmy hippos (Hexaprotodon liberiensis) and six banteng (Bos javanicus) on a diet of fresh grass at two intake levels. We used cobalt ethylendiamintetraacetate (Co-EDTA) as fluid and chromium (Cr)-mordanted fibre (2 mm) and cerium (Ce)-mordanted fibre (10 mm) as particle markers, mixed in the food. Average total tract MRT for fluid, small and large particles at the high intake level was 32, 76 and 73 h in pygmy hippos and 25, 56 and 60 h in banteng, and at the low intake level 39, 109, and 105 h in pygmy hippos and 22, 51 and 58 h in banteng, respectively. In accordance with the prediction, large particles moved faster than, or as fast as the small particles, through the gut of pygmy hippos. In contrast, large particles were excreted slower than the small particles in the ruminant of this study, the banteng. Pygmy hippos had longer retention times than the banteng, which probably compensate for the less efficient particle size reduction. Although the results were not as distinct as expected, most likely due to the fact that ingestive mastication of the larger particle marker could not be prevented, they confirm our hypothesis of a functional difference in selective particle retention between ruminating and non-ruminating foregut fermenters.

Irregular tooth wear and longevity in captive wild ruminants: a pilot survey of necropsy reports.

Tooth wear is often suggested as an important factor limiting the life span of free-ranging wildlife. Given the frequent occurrence of poor dental health in captive animals reported in the literature, one would expect tooth health to be a limiting factor in captivity as well. Additionally, it could be assumed that brachydont (browsing) animals are more susceptible to dental health problems than are hypsodont (grazing) animals, given current indications for systematic increased tooth wear in some browsing species. A pilot survey of necropsy reports of adult captive wild ruminants (n = 294, 12 species) in one facility was performed in order to test these hypotheses and to calculate the incidence of irregular tooth wear. The overall incidence of irregular tooth wear was 20%, with a very high proportion of reports that did not mention the teeth at all. In contrast to this study's hypotheses, animals with irregular tooth wear were older than animals that died from other causes, indicating that reaching above-average age was a prerequisite for the development of reported abnormalities in this data set. A grazing species (blackbuck, Antilope cervicapra) was most affected, whereas two browsing species were not affected. Affected species had been regularly fed on sandy soil, whereas browsers had received feeds from racks, indicating that husbandry practices are most important for dental health. There was a high proportion of reported serous fat atrophy in animals with irregular tooth wear, indicating the clinical relevance of the problem. On average, adult individuals of the species investigated reached 41% of the maximum reported life span. Although this number appears low, the lack of comparative data from other facilities does not allow for conclusions on the adequacy of the husbandry practices used.

Fluid and particle retention in the digestive tract of the addax antelope (Addax nasomaculatus)--adaptations of a grazing desert ruminant.

Retention time of food in the digestive tract is a major aspect describing the digestive physiology of herbivores. Differences in feed retention times have been described for different ruminant feeding types. In this study, a dominantly grazing desert ruminant, the addax (Addax nasomaculatus), was investigated in this respect. Eight animals with a body weight (BW) of 87+/-5.3 kg on an ad libitum grass hay (Chloris gayana) diet were available. Co-EDTA and Cr-mordanted fibers (<2 mm) were used as pulse-dose markers. Mean retention time (MRT) in the digestive tract was calculated from faecal marker excretion. Average daily intake of the addax was found to be 1.7 kg dry matter (DM) or 60+/-8.3 g DM/kg BW(0.75). The MRT of fluid and particles in the reticulo-rumen (MRT(fluid)RR and MRT(particle)RR) were quantified to be 20+/-5.8 and 42+/-7.0 h respectively. When compared to literature data, MRT(fluid)RR was significantly longer than in cattle species, and MRT(particle)RR was significantly longer than in 11 taxa of all feeding types. The ratio of MRT(particle)RR/MRT(fluid)RR (2.3+/-0.5) was found to be within the range described for grazing ruminants. The long retention times found in the addax can be interpreted as an adaptation to a diet including a high proportion of slow fermenting grasses, while the long retention time of the fluid phase can be interpreted as a consequence of water saving mechanisms of the desert-adapted addax with a potentially low water turnover and capacious water storing rumen.

Differences in fecal particle size between free-ranging and captive individuals of two browser species.

Data from captive animals indicated that browsing (BR) ruminants have larger fecal particles-indicative of lesser chewing efficiency-than grazers (GR). To answer whether this reflects fundamental differences between the animal groups, or different reactions of basically similar organisms to diets fed in captivity, we compared mean fecal particle size (MPS) in a GR and a BR ruminant (aurox Bos primigenius taurus, giraffe Giraffa camelopardalis) and a GR and a BR hindgut fermenter (Przewalski's horse Equus ferus przewalskii, lowland tapir Tapirus terrestris), both from captivity and from the wild. As would be expected owing to a proportion of finely ground, pelleted feeds in captive diets, MPS was smaller in captive than free-ranging GR. In contrast, MPS was drastically higher in captive than in free-ranging BR of either digestion type. Thus, the difference in MPS between GR and BR was much more pronounced among captive than free-ranging animals. The results indicate that BR teeth have adapted to their natural diet so that in the wild, they achieve a particle size reduction similar to that of GR. However, although GR teeth seem equally adapted to food ingested in captivity, the BR teeth seem less well suited to efficiently chew captive diets. In the case of ruminants, less efficient particle size reduction could contribute to potential clinical problems like "rumen blockage" and bezoar formation. Comparisons of MPS between free-ranging and captive animals might offer indications for the physical suitability of zoo diets. Zoo Biol 27:70-77, 2008. (c) 2007 Wiley-Liss, Inc.

Convergent evolution in feeding types: salivary gland mass differences in wild ruminant species.

In the ongoing debate about divergent evolutionary morphophysiological adaptations of grazing and browsing ruminants, the size of the salivary glands has received special attention. Here, we report the most comprehensive dataset on ruminant salivary glands so far, with data on the Glandula parotis (n=62 species), Gl. mandibularis (n=61), Gl. buccalis ventralis (n=44), and Gl. sublingualis (n=30). All four salivary gland complexes showed allometric scaling with body mass (BM); in all cases, the 95% confidence interval for the allometric exponent included 0.75 but did not include 1.0 (linearity); therefore, like other parameters linked to the process of food intake, salivary gland mass appears to be correlated to metabolic body weight (BM0.75), and comparisons of relative salivary gland mass between species should rather be made on the basis of BM0.75 than as a percentage of BM. In the subsequent analyses, the percentage of grass (%grass) in the natural diet was used to characterize the feeding type; the phylogenetic tree used for a controlled statistical evaluation was entirely based on mitochondrial DNA information. Regardless of phylogenetic control in the statistical treatment, there was, for all four gland complexes, a significant positive correlation of BM and gland mass, and a significant negative correlation between %grass in the natural diet and gland mass. If the Gl. parotis was analyzed either for cervid or for bovid species only, the negative correlation of gland mass and %grass was still significant in either case; an inspection of certain ruminant subfamilies, however, suggested that a convergent evolutionary adaptation can only be demonstrated if a sufficient variety of ruminant subfamilies are included in a dataset. The results support the concept that ruminant species that ingest more grass have smaller salivary glands, possibly indicating a reduced requirement for the production of salivary tannin-binding proteins.