Forage fibre digestion, rates of feed passage and gut fill in juvenile and adult red kangaroosMacropus rufusDesmarest: why body size matters

Abstract

SUMMARY Using red kangaroos Macropus rufus Desmarest, a large (>20 kg)marsupial herbivore, we compared the digestive capabilities of juveniles with those of mature, non-lactating females on high-quality forage (chopped lucerne Medicago sativa hay) of 43±1% neutral-detergent fibre (NDF)and poorer quality, high-fibre forage (chopped oaten Avena sativahay) of 64±1% NDF. On chopped lucerne apparent dry matter (DM)digestibilities by young-at-foot (YAF) red kangaroos (an age that would normally be taking some milk from their mother), weaned juveniles and mature females were similar (55–59%). On chopped oaten hay apparent DM digestibility was lower in the YAF (35.9±2.3%) followed by weaned(43.4±2.8%) and mature females (44.6±1%). The digestion of NDF and its components (mainly cellulose and hemicellulose) was lowest among the YAF followed by weaned and then mature females. The YAF and weaned kangaroos could not sustain growth on the poor-quality diet, and appeared to be at or near maximal gut fill on both forages; the values being 114–122 g DM for YAF and 151–159 g DM for weaned kangaroos. Mean retention times (MRT) of particle and solute markers were significantly longer for the YAF and weaned kangaroos on oaten hay than on lucerne hay, and DM intake (g d–1) was ∼50% lower on the oaten hay. In contrast, solute and particle MRTs in the mature females were not significantly affected by diet; they maintained DM intakes by increasing DM gut fill from 264±24 g on chopped lucerne to 427±26 g DM on chopped oaten hay. Clearly, the mature female kangaroos did not maximise gut fill on the high-quality forage,presumably as a consequence of their proportionally lower energy requirements compared with still-growing juveniles. Overall, we have provided the first mechanistic link between the physiological constraints faced by juvenile red kangaroos in relation to their drought-related mortalities, rainfall and forage quality.

Hindgut Plasticity in Wallabies Fed Hay either Unchopped or Ground and Pelleted: Fiber Is Not the Only Factor

“…1; Stevens and Hume 1995;Hume 1999). The kangaroo forestomach is typified by numerous haustrations that likely provide elastic support for physical flexibility in content loads, as was observed here (Table 2), probably facilitating reserve gut capacity under different nutritional circumstances (e.g., Munn and Dawson 2006;. In this study, we found that there was profound phenotypic plasticity of the hindgut, mainly in the proximal and distal colon but probably also in the cecum.…”

“…In macropodids, there is a marked separation of small and large particles in the foregut, with smaller particles and solutes exiting the tubiform forestomach faster than larger particles (Dellow 1982;Munn and Dawson 2006). Thus, as intakes of small particles increase, such as in animals receiving pelleted diets (Freudenberger and Hume 1992) or high-quality forage (inferred from ruminants and swine ;Grenet 1989;van Bruchem et al 1991;Robertson et al 1992), more bulk flow of potentially digestible material would pass to the lower gut.…”

Age, body mass and environmental variation shape the foraging ontogeny of Galapagos sea lions

“…This is especially problematic for juvenile mammals whose mass at weaning is often lower than adult mass and who often have not completed their morphological and physiological development. Incomplete morphological de -velopment can inhibit the handling of larger-sized prey items (Brito 2004, La Croix et al 2011 or the digestion of specific prey items (Munn & Dawson 2006), thus narrowing the choice of suitable prey, which in turn leads to differences in resource utilisation and foraging habitat between juveniles and adults (Wikelski & Trillmich 1994. Physiological limits (e.g.…”

Amelioration of Hepato-Renal Toxicity by a Flavonoid-Rich Fraction of Hibiscus rosa-sinenses (Leaves and Flowers) in Male Rabbits Intoxicated by Cadmium

“…Animals were kept in individual cages and were handled carefully under standard conditions of 12h dark light cycle in temperature 24±3ºC and relative humidity of 50-60%. Before commencing this experiment, all animals were injected with 0.1mL/Kg body weight ivermectin (s.c.) [19] to eradicate endo and ecto-parasites, followed by a week of adjustment period. This treatment, with ivermectin, will help to minimize the interference of parasites in the course of the study.…”