Carnivorous mammals: nutrient digestibility and energy evaluation

Abstract

Estimating the energy content is the first step in diet formulation, as it determines the amount of food eaten and hence the concentration of nutrients required to meet the animal's requirements. Additionally, being able to estimate the energy content of a diet empirically known to maintain body condition in an animal will facilitate an estimation of maintenance energy requirements. We collated data on nutrient composition of diets fed to captive wild canids, felids, hyenids, mustelids, pinnipeds, and ursids and the digestibility coefficients from the literature (45 species, 74 publications) to test whether differences in protein and fat digestibility could be detected between species groups, and whether approaches suggested for the estimation of dietary metabolizable energy (ME) content in domestic carnivores (NRC [2006] Nutrient requirements of dogs and cats. Washington, DC: National Academy Press.) can be applied to wild carnivores as well. Regressions of digestible protein or fat content vs. the crude protein (CP) or fat content indicated no relevant differences in the digestive physiology between the carnivore groups. For diets based on raw meat, fish, or whole prey, applying the calculation of ME using "Atwater factors" (16.7 kJ/g CP; 16.7 kJ/g nitrogen-free extracts; 37.7 kJ/g crude fat) provided estimates that compared well to experimental results. This study suggests that ME estimation in such diets is feasible without additional digestion trials. For comparative nutrition research, the study implicates that highly digestible diets typically fed in zoos offer little potential to elucidate differences between species or carnivore groups, but research on diets with higher proportions of difficult-to-digest components (fiber, connective tissues) is lacking.

Carbon isotopes in exhaled breath track metabolic substrates in brown bears (Ursus arctos)

“…We did not account for potential differences in efficiencies of digestion and assimilation of salmon protein, salmon lipid, and oil in the experimental diet because these processes tend to be efficient in bears (Clauss et al 2010;Pritchard and Robbins 1990). However, digestion and assimilation can differ among nutrients and monomers of nutrients (e.g., FAs- Apgar et al 1987) and should be considered when making dietary inferences based on d 13 C breath values.…”

Infanticide as a male reproductive strategy has a nutritive risk effect in brown bears

“…The digestive efficiency of brown bears is similar to those of obligate carnivores, and bears are not adapted to efficiently digest coarse forage [14]. Therefore, we used % dry faecal matter of faecal crude fibre content (FCF) and faecal protein content (FP) as proxies of diet quality in bears.…”

“…Therefore, we used % dry faecal matter of faecal crude fibre content (FCF) and faecal protein content (FP) as proxies of diet quality in bears. High-FCF content indicates low diet quality, whereas high-FP content indicates high quality [14]. …”

Comparison of methods for determination of nutrient digestibility of a dry kibble diet for ocelots

“…Lôbo Jr. et al (2001) reported that ADF underrated the CAD determined by total fecal collection, in contrast to Carciofi et al (1998), who deem CF and ADF efficient in this determination, but suggest the need for new studies to confirm such conclusion. Under these conditions, the reports of Vester et al (2008) and Clauss et al (2010), about the likelihood of microbial fermentation in the final portion of the small intestine and in the large intestine of small felines may justify the reduced CAD estimated by CF and ADF in the present experiment.…”

“…However, in captivity, diets are normally elaborated empirically, according to the choices and habits observed in wild animals, by trial and error and taking into account the body condition of each animal. Nevertheless, such factors may not be sufficient to attend the individual nutritional demands (Saad et al 2007, Clauss et al 2010.…”