RESUMEN
Six adult castrated male red deer (Cervus elaphus), fitted with rumen cannulas, were offered chaffed lucerne hay ad lib. during winter and summer, with voluntary food intake (VFI) being respectively 59 and 89 g dry matter intake (DMI)/kg bodyweight 0.75 per d. The same animals were also offered the same feed during summer, with intake restricted to that of winter VFI. The apparent digestibility of gross energy (0.60) or fibre (0.41) and the total capacity (volume) of the rumen were unaffected by season or level of intake. Relative to winter ad lib. feeding, N retention, total rumen pool size (DM + water), rumen pool size as a proportion of capacity, and rumen total volatile fatty acid (VFA) pool size were increased during summer ad lib. feeding. Relative to winter ad lib. feeding, N retention, rumen ammonia irreversible loss rate (IRL), total rumen pool size, rumen pool size as a proportion of capacity, and rumen ammonia and total VFA pool sizes were also increased during summer restricted feeding. Rumen lignin fractional disappearance rate (FDPR) was lower in summer than in winter, and there was a non-significant trend for rumen fractional outflow rate (FOR) of liquid to follow the same trend. Molar proportions of acetate and propionate were unaffected by season, proportions of n-butyrate were slightly higher in summer, and proportions of iso-butyrate and iso-valerate were higher for summer restricted than for winter ad lib. feeding. When intakes were equalized there were no seasonal changes in rate of rumen water outflow, net rumen water balance or intestinal water absorption. It is concluded that there is a seasonal change in rumen physiology in red deer during summer causing increased total rumen pool size (DM + water), an increase in rumen ammonia production and pool size, and an increase in rumen total VFA pool size which are all independent of the increase in VFI. The increased total rumen pool size in the summer restricted group may indicate an increased mean retention time (MRT) of digesta in the rumen. MRT for particulate matter was calculated to be 29.2 and 34.8 h during winter and summer respectively. This, together with increased rumen ammonia production, may function to maintain rumen fibre digestion when VFI normally increases during summer. The increased rumen VFA pool size may indicate increased VFA production during summer, in the same way as ammonia IRL was increased.
Asunto(s)
Alimentación Animal , Ciervos/metabolismo , Digestión/fisiología , Rumen/metabolismo , Estaciones del Año , Amoníaco/metabolismo , Animales , Masculino , Nitrógeno/metabolismoRESUMEN
1. Glucose pool size, space, entry rate, and turnover time were estimated from the specific radioactivity vs time curves of [3H] and [14C]glucose administered as a single injection in the euro (Macropus robustus erubescens) and the sympatric feral goat (Capra hircus). 2. Digestible energy intake was greater (P < 0.05 +/- SE) in the goat than in the euro (798 +/- 64 vs 624 +/- 31 kJ/kg0.75 x day). 3. However, there were no significant differences between the two species in parameters of glucose metabolism. 4. The use of an implantable osmotic infusion pump to deliver isotropic glucose showed promise as a means of avoiding the stress involved with the single injection technique.
Asunto(s)
Glucosa/metabolismo , Cabras/metabolismo , Macropodidae/metabolismo , Animales , Glucemia/metabolismo , Femenino , Especificidad de la EspecieRESUMEN
The effects of water restriction on digestive function in the euro (Macropus robustus erubescens) found in the arid zone of inland Australia, the eastern wallaroo (M.r.robustus) from more mesic regions of eastern Australia, and the feral goat (Capra hircus) found throughout the range of M. robustus, were compared in order to examine some physiological adaptations required by herbivores for the exploitation of arid environments. Eight animals of each species were held in individual metabolism cages in temperature-moderated rooms and given a chopped hay diet ad libitum. Half the animals were restricted to 40 ml water.kg-0.80.day-1. This was 40%, 32% and 57% of voluntary drinking water intake in the euro, wallaroo and goat, respectively. All species responded to water restriction by reducing faecal, urinary and evaporative water losses in association with reductions in feed intake. All animals increased urine osmolality and electrolyte concentrations but not to maximal levels, while packed-cell volume and plasma osmolality and electrolyte concentrations were unaffected by water restriction. The euro displayed a suite of characteristics that separated it from the wallaroo in terms of physiological adaptation, including lower voluntary water intake, an increase in fibre digestibility and maintenance of nitrogen balance during water restriction, and lower faecal water efflux associated with a consistently lower faecal water content (54% versus 59% water in the wallaroo during water restriction, P < 0.05). The euro's colon was 37% longer (P < 0.01) than that of the wallaroo. The goat had the lowest faecal water efflux (P < 0.05) and the longest colon (P < 0.001). Water restriction did not affect water content in digesta, nor short-chain fatty acid concentrations or production rates in vitro. Total body water, as a proportion of body mass, was depressed (P < 0.05) in the macropodids, but not in the goat. The reduction in dietary nitrogen intake, which accompanied water restriction, was partially compensated by an increase in urea degradation in the gut from 68% to 76% of urea synthesis water-restricted macropodids. These responses to water restriction are discussed in relation to those reported in other macropodid and ruminant species.