Effects Of Diet And Rumen Regulation On Nitrogen Metabolism,Urea Nitrogen Recycling And Microbial Protein Synthesis In Growing White Cashmere Goats

The experiment was conducted to study the effect of the different dietary levels and partial ruminal defaunation on nitrogen metabolism, the rumen environment, microbial protein synthesis and urea nitrogen recycling in the Inner Mongolia White Cashmere goats. The trials were divided into three parts.Part1Effects of dairy crude protein levels on nitrogen metabolism, the utilization of nitrogen and microbial protein synthesis in Growing Inner Mongolia White Cashmere GoatsThe first part was conducted to study the effects of dairy crude protein levels on nitrogen metabolism and microbial protein synthesis (MPS) in Growing Inner Mongolia White Cashmere Goats. Nine Inner Mongolia White Cashmere goats (43.83±2.95kg of initial BW) fitted with ruminal cannulas were blocked into3groups by initial BW. Goats were fed dietary crude protein levels (CP) of7.5(LOW),10.5(MID), and13.5%(HIGH) CP with similar amounts of metabolizable energy (ME) as dry matter intake. Conventional test methods were selected, for analysis of determination of feces N, urine N, UUN and PUN, and the urinary excretion of purine derivatives method was used to estimate microbial protein synthesis. The results showed that the ruminal concentration of NH3-N and butyrate were lower (P<0.01), whereas that of propionate was higher (P<0.05) and that of acetate and total VFA had no major difference in fed diet MID compared to HIGH; The ruminal concentration of NH3-N and propionate had no major difference (P>0.05), but that of acetate was lower (P<0.05) and butyrate was higher (P<0.05) in fed diet MID compared to LOW; The ruminal concentration of NH3-N and butyrate were higher (P<0.01), whereas that of acetate and propionate were higher (P<0.01) in fed diet HIGH compared to LOW. DM intake and urinary N output and urea-N (UUN) decreased (P<0.05), whereas N intake and N retention as a proportion of N intake increased (P<0.05) in fed diet MID compared to HIGH; DM intake decreased (P<0.05), but N intake, UUN, blood urea-N (PUN) and N retention as a proportion of N intake increased (P<0.05) in fed diet MID compared to LOW; DM intake decreased (P<0.05), whereas N intake feces N, urine N, UUN and PUN increased (P<0.01), and N retention as a proportion of N intake had no significant difference (P>0.05) in fed diet LOW compared HIGH. Allantoin, uric acid and total PD were higher (P<0.01), and MPS was higher (P<0.01).To sum up, the appropriate reduction of diet N was benefit to improve the utilization of N when the demand of microbial protein of animal was meet.Part2Effects of partial ruminal defaunation on nitrogen metabolism, the utilization of nitrogen and microbial protein synthesis in Growing Inner Mongolia White Cashmere Goats Fed LOW or HIGH Dietary Crude Protein ConcentrationsThe secend part was conducted to study the effects of partial ruminal defaunation on nitrogen metabolism and MPS in growing goats fed low (7.5%) or high (13.5%) dietary crude protein concentrations (DM basis).Twelve Inner Mongolia White Cashmere goats with half-sib castrated male goats (43.83±2.95kg of initial BW) were blocked by initial BW into4group, fitted with permanent cannulas in the rumen. The experiment used a2x2factorial randomized block design.The dietary factors studied were:(1) low nitrogen dietary vs. high nitrogen dietary and (2) partial defaunation (PDFAUN) vs. Faunation (FAUN). Sarsa-saponi ne was fed as anti-protozoal agent. The urinary excretion of purine derivatives method was used to estimate microbial NAN supply (Chen XB and ER Orsko,2004). Results showed that:(1) Feeding sarsa-saponine decreased (P<0.01) total ruminal protozoa by82and80%in goats fed diet LOW and HIGH. It indicated that the proportion of defaunation was higher in goats fed diet LOW.(2) Partial defaunation was accompanied by a decrease (P<0.05) in ruminal NH3-N,acetate and total VFA concentrations, a increase (P<0.01) in propionate concentrat ions, allantoin and total purine derivatives excretion compared to FAUN goats in fed diet LOW and HIGH.(3) The urinary N decreased2.24and1.52g/d, N retention as a proportion of N intake increased5.38and2.81%, and microbial NAN supply increased2.17and2.73g/d in PDFAUN goats compared to FAUN goats in fed diet LOW and HIGH, respectively. It indicated that the utilization of N was improved in PDFAUN goats in fed diet LOW and HIGH.(4) The level of dietary CP also altered the efficiency of N use. NH3-N, acetate and total VFA concentrations in rumina did not change significantly (P<0.05), allantoin and total PD excretion decreased in PDFAUN and FAUN goats in fed diet LOW compared to HIGH.(5) MPS decreased5.79and5.23g/d, but the urinary N decreased4.14and3.42g/d, N retention as a proportion of N intake increased3.14and0.57%in PDFAUN and FAUN goats in fed diet LOW compared to HIGH, respectively. It indicated that the utilization of N was improved in PDFAUN and FAUN goats in fed diet LOW. It is concluded that partial defaunation is benefit to improve the utilization of N in goats in fed diet LOW. Part3Effects of feeding oscillating dietray protein concentrations on nitrogen metabolism, the utilization of nitrogen and microbial protein synthesis in Growing Inner Mongolia White Cashmere GoatsThe third part was conducted to study the effects of feeding oscillating dietray protein concentrations on nitrogen metabolism, the utilization of nitrogen and MPS in Growing Inner Mongolia White Cashmere Goats. Nine Inner Mongolia White Cashmere goats (45.53±3.15kg of initial BW) fitted with ruminal cannulas were blocked into3groups by initial BW. Dietary treatments consisted of a medium CP diet (MEDIUM;10.5%CP) or diets with oscillating CP content (OSC) fed in two different sequences, for example2d of low CP (7.5%CP) followed by2d of high CP (13.5%CP; OSC-HIGH) or vice-versa (OSC-LOW) Results showed that:(1) PH and the ruminal concentrations of acetate, propionate and total VFA were lower (P<0.01), but NH3-N was higher (P<0.05) in goats in fed OSC. PH and the ruminal concentrations of propionate have no major difference (P>0.05), but that of the NH3-N was lower and acetate was higher in goats in OSC-LOW compared to OSC-HIGH.(2) DMI, N intake and PUN (P>0.05) have no a major difference, and the urinary N, fecal N and UUN were lower (P<0.01), but N retention and N retention as a proportion of N intake were higher (P<0.01) in goats in fed OSC.(3) Allantoin, total PD excretion and MPS were higher, but uric acid excretion was decreased (P<0.01) in goats in fed OSC.(4) GER (UUN entry to GIT) and UUA (Re-use for anabolism)/GER were increased (P<0.05), but UUE (Loss to urine), UUE/UER and ROC (Return to ornithine cycle)/GER were decreased in goats in fed OSC. It is concluded that feeding oscillating dietray protein concentrations is benefit to improve the utilization of N and MPS in Growing Inner Mongolia White Cashmere Goats. In conclusion, feeding oscillating dietray CP is benefit to improve the utilization of N and microbial protein synthesis compared to in goats in fed MID.