Utilization of endogenous and dietary urea in the large intestine of the mature horse

Abstract

The dynamics of N metabolism in mature horses were investigated when they were fed on a low-N diet or the same diet supplemented with sufficient urea or soyabean meal to meet their theoretical N requirements. There were no differences in DM, organic matter or neutral-detergent-fibre digestibilities for the three diets. N digestibilities and digestible-N intakes were similar for the urea-and soyabeansupplemented diets and very low for the low-N diet. For all three diets plasma urea was degraded in the digestive tract to NH, which was utilized by the bacterial population as a N source. NH, was absorbed from the large intestine into the blood and converted to urea. NH, was also incorporated into plasma proteins. The horses fed on the low-N diet degraded a greater proportion of endogenous urea in the digestive tract than did horses fed on the urea-or soyabean-supplemented diets. However, the horses fed on the urea diet had the highest degradation rate of urea. The quantity of urea degraded in the digestive tract of horses fed on the urea-supplemented and the low-N diets could not compensate for a lack of dietary crude protein in these diets. The horses were in a negative N balance when fed on the low-N and urea-supplemented diets and a positive N balance when fed on the soyabean-supplemented diet. Dietary urea supplementation did not benefit the horses. Urea: Nitrogen metabolism: HorseThere is some debate concerning the horse's ability to utilize urea. At present it is not known if dietary urea supplementation has a place in the horse industry, particularly in the case of mature horses grazing poor quality pastures. It has been shown that endogenous urea is degraded in the large intestine and the proportion of endogenous urea degraded increases with low-protein diets (Houpt & Houpt, 1971;Prior et al. 1974). These results indicate that horses utilize some endogenous urea and therefore it is possible that supplementary urea may be of nutritional benefit.The aim of the present experiment was to investigate the utilization of urea in the large intestine of the mature horse and to provide further information on the dynamics of N metabolism in horses fed on low-and adequate-protein diets. METHODS AnimalsThree adult geldings, two Standardbreds and one Arabian (average weight 400 kg), aged between 5 and 7 years were each surgically fitted with two polyvinyl chloride (PVC) cannulas which had an outside diameter of 15 nun and an internal diameter of 10 mm. One

A comparison of the microbiome and the metabolome of different regions of the equine hindgut

“…In this study, we attempted to link the microbial population to function using both targeted and nontargeted metabolic analysis. Ammonia measured in this study is somewhat higher than that reported (Hecker, 1971;Kern et al, 1974;Stott et al, 1983;Martin et al, 1996;Medina et al, 2002) with the exception of work by Wolter & Chaabouni (1979). Values obtained for VFAs (total and individual values) in this study are in agreement with the range previously reported in the literature (Hintz et al, 1971;Kern et al, 1973;Argenzio et al, 1974;Willard et al, 1977;Moore-Colyer et al, 2000;De Fombelle et al, 2003;Respondek et al, 2007;Daly et al, 2012).…”

“…Fermentation products in terms of VFAs and ammonia were analysed as specific metabolites, and FT-IR was utilised to give a more generalist view. Some ammonia is likely to be utilised by bacteria in the large intestine for growth and some potentially absorbed to be recycled to the small intestine (Bochröder et al, 1994;Martin et al, 1996). Ammonia measured in this study is somewhat higher than that reported (Hecker, 1971;Kern et al, 1974;Stott et al, 1983;Martin et al, 1996;Medina et al, 2002) with the exception of work by Wolter & Chaabouni (1979).…”

Evaluating the Technique of Using Nitrogen Retention as a Response Criterion for Amino Acid Studies in the Horse

“…As a result, there was an increase (P<0.01) in urinary nitrogen for data not scaled to body weight and data accounting for endogenous losses and scaled to body weight, as well as an increase (P < 0.05) in urinary nitrogen for data scaled to body weight and data accounting for endogenous losses but not scaled to body weight. Other research has also indicated little or no benefit to adding urea to the diet of horses (Godbee and Slade, 1981;Martin et al, 1996) and resulted in increased urinary nitrogen when urea was added (Glade and Biesik, 1986). …”

Avaliação de alimentos alternativos para cavalos adultos da raça Crioulo

“…Apesar de os melhores valores de digestibilidade da fração fibrosa terem sido obtidos com as dietas com casca de soja e casca de milho, estas dietas propiciaram também menores médias de digestibilidade para proteína bruta, provavelmente em razão da maior influência ou do aumento das perdas endógenas nas fezes, assim como da possível maior concentração de corpos microbianos oriundos de atividade fermentativa mais intensa na região do cecocólon dos animais alimentados com estas dietas (Figueiredo et al, 1999;Martin et al, 1996;Oliveira & Furtado, 2001;Oliveira et al, 2002). Como as dietas com casca de soja e casca de milho possuem menores teores de proteína e maiores teores de fibra, possíveis inferências sobre efeitos sinérgicos na digestibilidade dos nutrientes tornam-se plausíveis, pois indicam interatividade entre as características intrínsecas dos alimentos e mecanismos fisiológicos compensatórios no trato digestório dos animais (Swenson & Reece, 1996).…”