Utilisation of phytate phosphorus by rumen bacteria in a semi-continuous culture system (Rusitec) in lactating goats fed on different forage to concentrate ratios

Abstract

-Experimental data on phytate phosphorus utilisation by ruminants are scarce. The aim of this study was to estimate the phytase activity of rumen micro-organisms when phytate phosphorus supply is high. A semi-continuous culture system fermentor (RUSITEC) was used. The inoculum was obtained from eight goats fed on either high or low forage level diets. Experimental buffers only differed by the nature of phosphorus monosodium phosphate vs. corn sodium phytate. The nylon bags containing 15 g DM of substrate were removed after a 48-hour incubation period. The system was maintained for 15 days: 5 days for adaptation, in order to obtain a steady state, and 10 days for sampling and recording. No significant differences were observed for DM digestibility, gas production, pH, N-NH 3 , and SCFA for the different treatments. Bacterial efficiency of phytate phosphorus utilisation was significantly higher (p < 0.001) with organic P, but remained lower than the data usually reported in the literature. These results may be explained by the relative saturation of bacterial phytase activity when the buffer contains a high level of phytate phosphorus. phosphorus / phytate / ruminant / bacteria / in vitroRésumé -Mesure en fermenteur semi-continu (Rusitec) de l'utilisation du phosphore phytique par les bactéries du rumen chez la chèvre laitière recevant des régimes de différentes proportions fourrage-concentré. Les informations sur l'utilisation du phosphore phytique par les bactéries du rumen sont peu nombreuses. Le but de cet essai était d'évaluer in vitro (RUSITEC) l'efficacité de l'activité phytasique des micro-organismes recevant une proportion élevée de phosphore phytique. L'inoculum a été prélevé sur des chèvres recevant des régimes haut ou bas en aliment concentré. Dans les solutions nutritives, seule la nature du phosphore (phosphate monosodique vs. phytate de sodium de maïs) était différente. Les sachets nylon contenant 15 g de MS de substrat étaient maintenus 48 h Reprod. Nutr. Dev. 41 (2001) [259][260][261][262][263][264][265] 259

The effect of exogenous phytase supplementation on nutrient digestibility, ruminal fermentation and phosphorous bioavailability in Rambouillet sheep

“…reported that phytase supplementation did not affect ruminal NH 3 ‐N concentration. The lack of treatment effect on ruminal propionate and butyrate production suggests that supplemental phytase had no effect on gluconeogenesis and lipogenesis . In accordance with a previous study, phytase supplementation did not influence ruminal volatile fatty acids concentrations.…”

“…The decreased ruminal NH 3 -N levels of phytase supplemented groups at 3 h post feeding could either be the result of a reduction in the proteolytic bacteria population or an increased incorporation of the NH 3 -N into microbial protein as a result of improved microbial growth. 22 It is also possible that supplemental phytase reduced the ruminal degradability of dietary N. However, the effect of phytase supplementation on NH 3 -N became marginal and insignificant with an increasing hours of feeding. Ahmed et al 15 reported that phytase supplementation did not affect ruminal NH 3 -N concentration.…”

Effect of Phytase Supplementation on Rumen Fermentation Characteristics and Phosphorus Balance in Lactating Dairy Cows

“…A study by Clark et al (1986) pointed out that 98% of dietary InsP6 was hydrolysed to inorganic P (Pi) in the gastrointestinal tract of dairy cows. However, in vitro investigations by Godoy and Meschy (2001) showed that in specific situations the ruminal phytase hydrolyses not all P from InsP6. They carried out an experiment with a semi-continuous culture system, infusing Pi or a phytate source into the system.…”

Influence of supplemental phytase on growth performance, digestion and phosphorus balance of lambs fed sorghum-based diets

“…Therefore, P availability could be increased by phytase, and then enhance enzyme systems of ruminal microor- ganisms and fermentation of structural carbohydrates (Durand and Komisarczuk, 1988), such as that found on total tract digestion of NDF. In fact, high-grain diets (70%) and low pH induces disturbances in P excretion (Harmon and Britton, 1983) reducing native phytase activity (Godoy and Meschy, 2000). Phytase supplementation improved P digestion and retention, but it was not enough to change P excretion and serum levels as was reported by Knowlton et al (2007).…”