Mineral absorption in the black rhinoceros (Diceros bicornis) as compared with the domestic horse

To test whether mineral recommendations for horses are likely to guarantee adequate mineral provision for black rhinoceroses (Diceros bicornis), we investigated the apparent absorption (aA) of macro- and microminerals in eight black rhinoceroses from three zoological institutions in a total of 32 feeding trials with total faecal collection, with additional data from three unpublished studies (18 feeding trials). Feeds and faeces were analysed for Ca, P, Mg, Na, K, Fe, Mn, Cu, Zn and Co. The resulting aA coefficients, and the linear relationships of apparently absorbable dietary mineral content to total dietary mineral content [per 100 g dry matter (DM)], were compared with data for domestic horses. Rhinoceroses had significantly higher aA coefficients for Ca and Mg (because of a higher calculated 'true' absorption), and lower ones for Na and K (because of calculated higher endogenous faecal losses). High absorption efficiency for divalent cations is hypothesized to be an adaptation to a natural diet of particularly high Ca:P ratio (approximately 14:1); an effective removal of Ca from the ingesta guarantees sufficient P availability at the fermentation site in the hindgut. Higher faecal losses of Na and K are hypothesized to be linked to a higher faecal bulk per DM intake in black rhinoceroses as compared with horses because of a generally lower digestive efficiency. There were no relevant differences in the absorption patterns of microminerals. In particular, there were no discernable differences in Fe absorption within the rhinoceroses for diets with and without tannin supplementation. Several of the zoo diets assessed in this study were deficient in Cu, Mn or Zn, and most contained excessive levels of Fe when compared with horse requirements. The findings of this study indicate that differences in mineral absorption between occur even between species of similar digestive anatomy; that in particular, Ca absorption might vary between hindgut fermenters with Ca:P ratio in their natural diet; that Na might be a particularly limiting factor in the ecology of free-ranging rhinoceroses; that moderate doses of tannins do not seem to markedly influence mineral absorption; and that diets for captive animals should contain adequate, but not excessive mineral levels

Digestion coefficients achieved by the black rhinoceros (Diceros bicornis), a large browsing hindgut fermenter

In contrast to the grazing white (C. simum) and Indian (R. unicornis) rhinoceros, the black rhinoceros (D. bicornis) is an exclusive browser. Due to the particular fermentation characteristics of browse, one would expect browsers to display both shorter ingesta retention times and lower digestion coefficients on comparable diets than grazers. In order to generate a database to test this hypothesis, we performed digestibility studies in eight black rhinoceroses (D. bicornis) from three zoological institutions, using total faecal collection for the quantification of faecal output. One to three regularly fed zoo rations of roughage, concentrates and varying proportions of browse material were used per animal. Additional data was taken from three hitherto unpublished studies as well as several published sources. When compared with horses on similar rations, black rhinoceroses achieved lower digestion coefficients for organic matter and CF. In general, an increase in dietary CF content led to a steeper decrease in organic matter and GE digestibility in black rhinoceroses than in horses. When comparing available data for rhinoceroses, browsing species showed a steeper decrease in organic matter digestibility than grazing species with increasing dietary cell wall content. Endogenous losses as determined by linear regression analysis were within the range reported for horses and Indian rhinoceroses. The results suggest that the horse is not a useful model animal for evaluating diets for black rhinoceroses energetically. In general, diets fed to captive black rhinoceroses seem to include higher proportions of concentrates than diets for other rhinoceros species, and an increase in browse or roughage would reduce digestion coefficients to levels observed in animals fed natural forage

Avaliação de Períodos de Coleta Total de Fezes para Determinar a Digestibilidade Aparente dos Nutrientes em Eqüinos Valuation of Fecal Total Collection Period to Determinate the Apparent Digestibility of Nutrients in Equine

Foram conduzidos dois ensaios de digestão, objetivando comparar os valores de digestibilidade dos nutrientes da cana-de-açúcar e cana-de-açúcar mais milho, em diferentes dias de coleta de fezes. Foram utilizados cinco e quatro cavalos adultos sem raça definida no primeiro e segundo ensaios, respectivamente, com idade média de seis anos. Os animais foram distribuídos aleatoriamente em blocos casualizados, em que cada cavalo constituiu o bloco, e os dias de coleta de fezes, os tratamentos. No primeiro ensaio, foi avaliada a digestibilidade da cana-de-açúcar em seis dias de coleta de fezes (2, 3, 4, 5, 6 e 7 dias), e no segundo ensaio, estimou-se a digestibilidade da cana-de-açúcar e milho em cinco dias de coletas de fezes (2, 3, 4, 5 e 6 dias). Não foram verificadas diferenças (P>0,05) entre os dias de coleta de fezes para estimar a digestibilidade dos nutrientes da cana-de-açúcar e cana-de-açúcar mais milho, porém, verificou-se aumento (P<0,05) na digestibilidade da PB da cana-de-açúcar com milho, na coleta de dois dias. Os períodos de coleta total de fezes de dois a sete dias, para ensaios de digestão com eqüinos alimentados apenas com volumosos, e de três a seis dias, para eqüinos submetidos a dietas mistas, mostraram-se bastante precisos. Dessa forma, sugere-se um período de cinco dias como forma de padronização de metodologia em ensaios de digestão com eqüinos.<br>ABSTRACT - Two digestion assays were carried out, with the objective to compare digestibility of sugar cane and sugar cane plus corn nutrients, in different fecal collection days. Five and four adult horses, without a defined breed and averaging 6 years of age, were utilized in assay 1 and 2, respectively. A randomized block design was used, with each horse considered as block and the days of fecal collection as treatments. In assay 1, the digestibility of sugar cane in six days of the fecal collection (days 2, 3, 4, 5, 6 and 7) was evaluated; and in assay 2, the digestibitlity of sugar cane plus corn over five days of fecal collection ( days 2, 3, 4, 5 and 6) was estimated. There were no significance (P>0.05) between days of fecal collection to estimate digestibility of sugar cane and sugar cane plus corn nutrients. However, an increase (P<0.05) in the digestibility of the CP of the sugar cane plus corn, on the second day of collection was observed. The utilization of three to six and two to seven days of total fecal collection in digestion assays which equines, feed with a mixed diet or solely roughage, respectively, was very precise, and a standard five day, period is recomended