Joaquim Balcells

Excretion of purine derivatives in cows: endogenous contribution and recovery of exogenous purine bases

Two dry cows fitted with simple cannula in the rumen and duodenum, and fed with a mixed diet (straw:barley, 50:50), were used to determine endogenous losses and response of urinary purine derivatives (PDs) to duodenally infused yeast-RNA. Duodenal flow of purine bases (PBs) was determined by a dual marker system, and 15N was infused continuously into the rumen to label microbial PBs. The isotope dilution of urinary PDs in relation to duodenal PBs confirmed the presence of an endogenous fraction (236 μmol/kg LW0.75) bigger than in sheep and lower than values estimated in cows with impaired rumen fermentation. Excretion of PDs increased linearly in response to incremental supply of PBs with an equimolar recovery of 0.84 mol/mol. However, net recovery of duodenal PBs was 0.67 for the basal diet and 0.65, 0.90, 0.79 and 0.82 for the four levels of PB infusion. It is suggested that differences in digestibility between yeast-RNA and duodenal PBs might explain differences in recovery estimations.

Protein recycling in growing rabbits: contribution of microbial lysine to amino acid metabolism

To study the absorption of microbial lysine in growing rabbits, a labelled diet (supplemented with (15)NH4Cl) was administered to six animals (group ISOT); a control group (CTRL, four rabbits) received a similar, but unlabelled, diet. Diets were administered for 30 d. An additional group of six animals were fed the unlabelled diet for 20 d and then the labelled diet for 10 d while wearing a neck collar to avoid caecotrophy (group COLL), in order to discriminate it from direct intestinal absorption. At day 30 animals were slaughtered and caecal bacteria and liver samples taken. The (15)N enrichment in amino acids of caecal bacteria and liver were determined by GC-combustion/isotope ratio MS. Lysine showed a higher enrichment in caecal microflora (0.925 atom% excess, APE) than liver (0.215 APE) in group ISOT animals, confirming the double origin of body lysine: microbial and dietary. The COLL group showed a much lower enrichment in tissue lysine (0.007 (se 0.0029) APE for liver). Any enrichment in the latter animals was due to direct absorption of microbial lysine along the digestive tract, since recycling of microbial protein (caecotrophy) was avoided. In such conditions liver enrichment was low, indicating a small direct intestinal absorption. From the ratio of [(15)N]lysine enrichment between liver and bacteria the contribution of microbes to body lysine was estimated at 23 %, with 97 % of this arising through caecotrophy. Absorption of microbial lysine through caecotrophy was 119 (se 4.0) mg/d, compared with 406 (se 1.8) mg/d available from the diet. This study confirms the importance of caecotrophy in rabbit nutrition (15 % of total protein intake).

Purine derivatives excretion in lactating ewes fed straw diets with different levels of fish meal

Abstract Purine derivatives (allantoin, uric acid, xanthine and hypoxanthine) concentration in blood, urine and milk samples, from a group of 20 lactating ewes, were analysed by high performance liquid chromatography (HPLC). The mammary gland contributed, together with the kidney and salivary glands, to purine derivative (PD) excretion. Daily excretion of PD and allantoin in milk were 280 ± 22.9 and 178 ± 10.7 μmol day−1, respectively, representing 2.2 ± 0.16 and 1.6 ± 0.10% respectively of the total (mammary plus renal) excretion. Problems with the endogenous uric acid contribution of the mammary gland to milk PD excretion are discussed. Measurements of PD losses in milk would improve the efficiency of response models relating duodenal flow of purine bases with urinary excretion of PD, although milk PD excretion in ewes does not seem to be a reliable alternative to such methodologies.

Urinary excretion of purine derivatives as an index of microbial protein synthesis in the camel (Camelus dromedarius).

Five experiments were carried out to extend knowledge of purine metabolism in the camel (Camelus dromedarius) and to establish a model to enable microbial protein outflow from the forestomachs to be estimated from the urinary excretion of purine derivatives (PD; i.e. xanthine, hypoxanthine, uric acid, allantoin). In experiment 1, four camels were fasted for five consecutive days to enable endogenous PD excretion in urine to be determined. Total PD excretion decreased during the fasting period to 267 (SE 41.5) micromol/kg body weight (W)0.75 per d. Allantoin and xanthine + hypoxanthine were consistently 86 and 6.1 % of total urinary PD during this period but uric acid increased from 3.6 % to 7.4 %. Xanthine oxidase activity in tissues (experiment 2) was (micromol/min per g fresh tissue) 0.038 in liver and 0.005 in gut mucosa but was not detected in plasma. In experiment 3, the duodenal supply of yeast containing exogenous purines produced a linear increase in urinary PD excretion rate with the slope indicating that 0.63 was excreted in urine. After taking account of endogenous PD excretion, the relationship can be used to predict purine outflow from the rumen. From the latter prediction, and also the purine:protein ratio in bacteria determined in experiment 5, we predicted the net microbial outflow from the rumen. In experiment 4, with increasing food intake, the rate of PD excretion in the urine increased linearly by about 11.1 mmol PD/kg digestible organic matter intake (DOMI), equivalent to 95 g microbial protein/kg DOMI.

Urinary excretion of purine derivatives in Bos indicus × Bos taurus crossbred cattle

Four experiments were performed to study the kinetics of purine metabolism and urinary excretion in Zebu crossbred cattle. Fasting excretion was established in Expt 1, using eighteen male Bos indicus x Bos taurus crossbred cattle (261 (SE 9.1) kg body weight), six of each of the following genotypes: 5/8 Bos indicus, 1/2 Bos indicus and 3/8 Bos indicus. No significant differences were observed among genotypes in fasting purine derivative excretion (277.3 (SE 35.43) micromol/metabolic body weight). In a second experiment we measured the xanthine oxidase activity, which was higher in liver than in duodenal mucosa (0.64 and 0.06 (SE 0.12) units/g wet tissue per min respectively; P>0.05) being in plasma 0.60 (SE 0.36) units/l per min. The kinetics of uric acid were measured by intravenous pulse dose of [1,3-15N]uric acid (Expt 3). The cumulative recovery of the isotope in urine was 82 (SE 6.69) %, and uric acid plasma removal, pool size and mean retention time were 0.284 (SE 0.051) per h, 5.45 (SE 0.823) mmol and 3.52 (SE 0.521) h, respectively. Allantoin was removed from plasma at an estimated fractional rate of 0.273 (SE 0.081) per h and mean retention was 3.66 (SE 1.08) h. In Expt 4, the relationship between urinary purine derivative excretion (Y; mmol/d) and digestible organic matter intake (X, kg/d) was defined by the equation: Y=7.69 (SE 4.2)+5.69 (SE 1.68) X; n 16, Se 1.31, r 0.67.

The influence of drinker device on water use and fertiliser value of slurry from growing-finishing pigs

This study assessed the effect of drinker type on water use and slurry characteristics of growing-finishing pigs. A total of 124 crossbred pigs [20 kg of bodyweight (BW)] were allotted to 16 pens (3–4 pigs/pen) in two time periods during the cool season (length: 97 days each). Drinker devices were: (1) pig teat, (2) bite drinker, (3) nipple square bowl, and (4) nipple bowl. There were limited differences among drinker types concerning the growth pattern of pigs during the fattening period, but target BW (100 kg) was similar in all treatments (P > 0.05). Feed intake did not differ among drinker types (P > 0.05). Nipple bowl drinker showed the lowest water disappearance during the experiment, whereas bite drinker showed the greatest values during the late fattening period (P 0.05), but slurry volume increased linearly during the study (P < 0.05). Pigs raised using nipple square and nipple bowl drinkers produced slurry with greater DM content than teat drinkers (P < 0.05). Most of the slurry fertiliser value elements (N-P-K) were significantly affected by drinker type (P < 0.05). Slurry from pigs using teat and bite drinkers had lower N-NH4, total N and K content than that from nipple square and nipple bowl drinkers (P < 0.05). Total N content of slurry on a wet basis decreased during the fattening period (P < 0.05). Improved efficiency in water use by pigs led to greater slurry N and K content, mainly due to the increase in its DM content. A negative association between water use at pig facilities and its slurry fertiliser value was demonstrated.

Contribution of gut microbial lysine to liver and milk amino acids in lactating does

The contribution of microbial amino acids through caecotrophy to tissue protein metabolism was investigated in lactating does. Attempts were made to vary microbial supply through a dietary antibiotic, Zn bacitracin, and to vary tissue demand through manipulation of litter size. Three groups of eight New Zealand does were fed different experimental diets from day 28 of pregnancy to day 26 of lactation. The control group received the basal diet formulated to meet requirements with grass hay, wheat, soybean meal and barley grain. The second (no antibiotic) group and the third (bacitracin; BAC) group ingested the basal diet supplemented with ammonium sulfate (5 g/kg), initially unlabelled (day 1 to day 8) then labelled with 15N (day 9 to day 30), while the BAC diet was also supplemented throughout with antibiotic (Zn bacitracin; 100 mg/kg). From just after birth each group of does was subdivided into two groups, each of four females, with the litter size either five (LS5) or nine (LS9) pups. The 15N enrichment in liver, milk and caecal bacteria amino acids was determined by GC-combustion-isotope ratio MS. All amino acids in bacterial protein were enriched with the (15 NH 4)2SO4 treatment, with lysine 15N enrichment significantly greater in caecal bacteria (0.23 (SE 0.0063) atom % excess (ape)) than in liver (0.04 (SE 0.0004) ape) or milk protein (0.05 (SE 0.0018) ape), confirming the double origin (bacterial and dietary) of tissue lysine. The contribution of microbes to tissue lysine was 0.23 (SE 0.006) when milk protein was used as reference.

Effects of the citrus flavonoid extract Bioflavex or its pure components on rumen fermentation of intensively reared beef steers

Two experiments were performed to study the effects of the citrus flavonoid extract Bioflavex (BF; Interquim SA, FerrerHealthTech, Sant Cugat, Barcelona, Spain) or its components on the rumen fermentation of a high-concentrate diet. In an in vivo experiment, eight Friesian steers (398 ± 12.2 kg bodyweight) fitted with a rumen cannula were given a basal concentrate (CTR) or a CTR supplemented with BF (450 mg/kg dry matter, DM) in a 2 × 4 crossover design. No differences were observed in performance parameters of BF and CTR steers. Diet BF increased pH values and the molar proportion of propionate and reduced lactate concentration as a result of an increase in the relative abundance of lactate-consuming microorganism Selenomomas ruminantium (P < 0.01) and Megaesphaera elsdenii (P = 0.06). In an in vitro experiment, the effect of BF and its pure flavonoid components added to the incubation medium was studied separately. Bioflavex and its main components naringine, neohesperidine (NH) and poncirine (PC) were added to the incubation medium at 500 µg/g DM, with the unsupplemented substrate also included as a control (CTR). After 12 h of incubation, flavonoid mixture and NH and PC reduced (P < 0.01) the volume of gas produced and the molar proportion of acetate (P < 0.01), and increased that of propionate (P < 0.01). PC reduced the relative quantification of Streptococcus bovis, whereas NH and BF increased the relative quantification of M. elsdenii in relation to CTR (P < 0.01). Bioflavex supplementation in steers in feedlot was effective in preventing a collapse in pH and it enhanced rumen fermentation efficiency through modifying the activity of lactate-consuming bacteria and a greater molar proportion of propionate and a reduction of that of acetate, suggesting its positive role in modulating the activity of rumen microbiota.