Energy supply of the okapi in captivity: intake and digestion trials

In the nutrition of browsing ruminants in captivity, adequate nutrient digestibility and energy content of diet is debated. Problems related to energy-provision and low forage intake have been reported for the okapi and other browsers like the giraffe, particularly during winter. High-fiber concentrates like unmolassed beet pulp have some potential to improve the nutritional management of these species. Using a total of six okapis in captivity, seven feeding trials were carried out at two facilities (A+B) on a structured but opportunistic base. Three trials (A(1), A(2), B-1) were conducted when animals were fed their regular diet including grain based energy concentrates, fruits and vegetables, and alfalfa (Medicago sativa) hay. Two trials (A(5), B-2) examined the effect of unmolassed beet pulp, and two (A(3,4)) examined the effect of unmolassed beet pulp+fresh browse. Daily intake and feces production were quantified over 8-12 days. Samples were analyzed for dry matter, crude ash, neutral detergent fiber (NDF)/acid detergent fiber (ADF)/acid detergent lignin (ADL), crude protein, and gross energy. Metabolizable energy content of diets was estimated via a factor (0.83) from digestible energy. The proportion of beet pulp in diets was 13% (A(3)), 24% (A(4)), 20% (A(5)) and 21% (B-2). Browse proportion was 11% (A(3)) and 32% (A(4)). Daily feed intake ranged between 1.5-1.7% of body weight (BW), digestibility of organic matter between 61-74%. Digestibility of fiber (NDF) was higher in beet pulp diets (A(3) = 39%, A(4)=60%, A(5)=54%, B-2=61%) than in the others (A(1)=48%, A(2)=33%, B-1 = 48%). Supply of metabolizable energy (ME) ranged between 0.50-0.70 MJ ME/(kg BW(0.75*)day), meeting energy requirements of okapis of 0.50-0.53MJ ME/(kg BW(0.75*)day) in general. Diets with beet pulp+browse were not found to be highest, but in the upper level of the range of forage proportions of this study. Palatable browse species were preferred over all other feedstuff offered. The use of unmolassed beet pulp as energy-concentrate for browsing ruminants like the okapi can be recommended because diets high in this high-fibre feedstuff resulted in adequate energy intakes

In vitro digestibility of fern and gymnosperm foliage: implications for sauropod feeding ecology and diet selection

Sauropod dinosaurs, the dominant herbivores throughout the Jurassic, challenge general rules of large vertebrate herbivory. With body weights surpassing those of any other megaherbivore, they relied almost exclusively on pre-angiosperm plants such as gymnosperms, ferns and fern allies as food sources, plant groups that are generally believed to be of very low nutritional quality. However, the nutritive value of these taxa is virtually unknown, despite their importance in the reconstruction of the ecology of Mesozoic herbivores. Using a feed evaluation test for extant herbivores, we show that the energy content of horsetails and of certain conifers and ferns is at a level comparable to extant browse. Based on our experimental results, plants such as Equisetum, Araucaria, Ginkgo and Angiopteris would have formed a major part of sauropod diets, while cycads, tree ferns and podocarp conifers would have been poor sources of energy. Energy-rich but slow-fermenting Araucaria, which was globally distributed in the Jurassic, was probably targeted by giant, high-browsing sauropods with their presumably very long ingesta retention times. Our data make possible a more realistic calculation of the daily food intake of an individual sauropod and improve our understanding of how large herbivorous dinosaurs could have flourished in pre-angiosperm ecosystems