Profils et taux de renouvellement en minéraux dans le pré-estomac de dromadaires pâturant en diverses saisons au Kenya

Les volumes et les taux de renouvellement du liquide des pré-estomacs ont été mesurés sur quatre dromadaires adultes fistulés entretenus sur pâturage dans les savanes arbustives à épineux du Kenya. Simultanément, les concentrations en minéraux et leur renouvellement ont été déterminés dans les compartiments C1 (rumen) et C2 (réseau). Les études ont été menées durant la saison humide et durant la saison sèche ; les comportements alimentaires ont été observés pour déterminer les régimes. Les volumes du liquide du pré-estomac n’étaient pas différents d’une saison à l’autre mais les taux de renouvellement du liquide étaient beaucoup plus bas en saison sèche. Les profils de concentration en minéraux Na, K, Ca, Mg et en phosphore inorganique variaient dans la journée selon les différents régimes alimentaires et probablement la production de salive. Le renouvellement journalier des cinq minéraux, dans les pré-estomacs a diminué durant la saison sèche

Methane emission by Camelids

Methane emissions from ruminant livestock have been intensively studied in order to reduce contribution to the greenhouse effect. Ruminants were found to produce more enteric methane than other mammalian herbivores. As camelids share some features of their digestive anatomy and physiology with ruminants, it has been proposed that they produce similar amounts of methane per unit of body mass. This is of special relevance for countrywide greenhouse gas budgets of countries that harbor large populations of camelids like Australia. However, hardly any quantitative methane emission measurements have been performed in camelids. In order to fill this gap, we carried out respiration chamber measurements with three camelid species (Vicugna pacos, Lama glama, Camelus bactrianus; n = 16 in total), all kept on a diet consisting of food produced from alfalfa only. The camelids produced less methane expressed on the basis of body mass (0.3260.11 L kg21 d21) when compared to literature data on domestic ruminants fed on roughage diets (0.5860.16 L kg21 d21). However, there was no significant difference between the two suborders when methane emission was expressed on the basis of digestible neutral detergent fiber intake (92.7633.9 L kg21 in camelids vs. 86.2612.1 L kg21 in ruminants). This implies that the pathways of methanogenesis forming part of the microbial digestion of fiber in the foregut are similar between the groups, and that the lower methane emission of camelids can be explained by their generally lower relative food intake. Our results suggest that the methane emission of Australia’s feral camels corresponds only to 1 to 2% of the methane amount produced by the countries’ domestic ruminants and that calculations of greenhouse gas budgets of countries with large camelid populations based on equations developed for ruminants are generally overestimating the actual levels

Differences in selective reticulo-ruminal particle retention as a key factor in ruminant diversification

The measurement of passage rate is important for the concept of ruminant diversification. While supporters of Hofmann's 1989 feeding type classification claim that browsing ruminants have faster passage rates than grazing ruminants, other researchers consider the passage rate to depend on body size alone. To date, no convincing comparison of ruminant passage rates has been put forward. For comparative purposes, we suggest the use of the "selectivity factor", which is an expression of how much longer particles of a defined size (<2 mm) are retained in the ruminant digestive tract than fluids. From the limited data available, it seems that grazing ruminants display selectivity factors between 1.56 and 3.80, whereas browsers have a much narrower range of 1.14-1.80. This suggests that browsers are not able to selectively retain particles as long as grazers. Intake of browsers, on the other hand, may not be limited by physical fill of the forestomach to the same degree as in grazers. This result can explain several observations on the digestive physiology of browsers, some of which have been linked to a rumen bypass mechanism. We propose that the ability for selective particle retention is a key factor for understanding the physiological consequences of ruminant diversification

Selektive Retention von Futterpartikeln verschiedener Groesse im Magen-Darmkanal von Kamelen im Vergleich mit Rindern und Schafen im Sudan

Available from: Zentralstelle fuer Agrardokumentation und -information (ZADI), Villichgasse 17, D-53177 Bonn / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Differences in the range of faecal dry matter content between feeding types of captive wild ruminants

The dry matter content of 245 faecal samples of 81 species of captive wild ruminants was investigated. Samples were taken from 10 different zoos from temperate climate during the winter months. All animals had ad libitum access to drinking water. Species were classified as frugivores (FR, n = 5), browsers (BR, n = 16), intermediate feeders (IM, n = 35), and grazers (GR, n = 25). While no difference was observed in the average faecal dry matter content between the feeding types, the range of dry matter contents increased continually from FR, BR, IM to GR, ie both the driest and the wettest faeces of this study were produced by grazing ruminants. As it has been shown that faecal dry matter content is a function of the length of the colon descendens of a ruminant species, these results can be interpreted as an indication of a relatively limited variation in anatomical design in this respect in the evolutionary older FR and BR, and a relatively larger variation in anatomical design - and probably niche adaptation - in IM and GR. This corresponds to the greater range of habitat niches that IM and GR manage to occupy. Due to this increased variation in the anatomical design of the lower hindgut, GR are regarded as "morphophysiologically progressive ruminants", in contrast to BR which are regarded as "morphophysiologically conservative ruminants"

No distinct difference in the excretion of large particles of varying size in a wild ruminant, the banteng (Bos javanicus)

The forestomach of ruminants and camelids does not only allow a differential excretion of fluids and small particles, but also a differential excretion of small and large particles. The question whether larger particles of different size classes are also retained for different time periods, or whether simply a particle size threshold exists above which all particles of a size higher than this threshold are retained in an undifferentiated manner, has not been addressed so far. We determined the mean retention time (MRT) of different sized large particles (10 and 20 mm) in three banteng (Bos javanicus) on two forage only diets, grass and grass hay. We used cerium (Ce)-mordanted fibre (10 mm) and lanthanum (La)-mordanted fibre (20 mm) as particle markers, mixed in the food. Average total tract MRT for large and very large particles at the grass diet was 58 and 56 h, and at the grass hay diet 66 and 64 h, respectively. Very large particles moved slightly faster than large particles through the gut of the banteng. Three interpretations are possible: Very large particles are resubmitted to rumination sooner than large particles. Ingestive mastication of the particle markers could have reduced the difference in the size of the particle markers; alternatively, particle retention may be governed by a threshold, above which all particles of a size higher than this threshold are retained in an undifferentiated manner. In order to test these possibilities, experiments with fistulated animals would have to be performed