Nitrogen metabolism and urinary excretion of purines in goat kids

1. In Expt 1 three male goat kids of the Swedish Landrace breed were bottle-fed on isoenergetic liquid diets composed of goat's milk alone or substituted with 200, 400, 600 and 800 ml of a nitrogen-free liquid diet/l. The goat kids were 3 weeks old at the start of the experiment and weighed on average 5.3 (SD 0.22) kg. The experiment lasted for 45 d divided into nine 5 d periods. The goat kids were kept individually in metabolism cages, and faeces and urine were collected daily. 2. In Expt 1 there was a significant (P less than 0.001) relation between N intake and N retention, with an estimated (extrapolation) basal N excretion of 211 mg N/kg metabolic live weight (W0.75). While the creatinine excretion remained fairly constant (19.9 mg/W0.75), there was a tendency for both the allantoin and uric acid excretions to change with N intakes. Hypoxanthine showed no consistent excretion pattern, and xanthine could not be detected. 3. In Expt 2 three male goat kids of the Swedish Landrace breed were used to study the effect of level of intake on N and purine metabolism. The first experimental period (period 1) started at 2 weeks of age (5.5 kg live weight) and the second experimental period (period 2) at 9 weeks of age (9.8 kg live weight). The goat kids were bottle-fed on goat milk at intended intakes of 400, 600, 800 and 1000 kJ gross energy/kg W0.75. Each treatment was given for 7 d with adaptation for 3 d and collections for 4 d. 4. In Expt 2 there were significant (P less than 0.001) increases in both live weight and N retention when level of intake was increased. With increasing N intakes both total N and urea-N excretions increased significantly (P less than 0.05). The proportions of urea-N and ammonia-N were fairly constant within periods, and were on average respectively 0.81 and 0.059 in period 1 and 0.84 and 0.068 in period 2. There was no significant effect of treatment on the urinary excretion of allantoin, hypoxanthine, xanthine and creatinine. In period 2 uric acid excretion was significantly (P less than 0.01) affected by the treatments. 5. From the presented findings it is concluded that the endogenous urinary excretion of purine derivatives in a young growing ruminant was only marginally affected by large variations in protein supply, and also by the level of intake of milk.

Estimation of microbial nitrogen in nylon-bag residues by feed 15N dilution

Rapeseed (Brassica napus), barley grain, ryegrass (Lolium perenne) and barley straw were labelled with 15N as an internal marker. The dilution of 15N was used to estimate microbial N (RMN15N) in the feed residues in nylon bags incubated in the rumen for 5, 12 and 24 h. For comparative purposes, diaminopimelic acid (DAP) content of the residues was also determined and rumen microbial N (RMNDAP-N) in the feed residues calculated using DAP as a bacterial marker. The influence of two bag pore sizes (20 microns and 40 microns) with different sample sizes (1 g and 5 g respectively) was also studied. For all feeds, the average disappearance of 15N was faster than that of total N, the difference between N and 15N disappearance being marked with barley, ryegrass and barley straw. The disappearance of microbially corrected dry matter (DM; correction calculated from the 15N values) was, accordingly, always faster than the uncorrected DM disappearance. Except for the bag pore/sample size effect for N disappearance, significant (P less than 0.01-0.001) feed, pore/sample size and incubation-time effects were always found for the disappearance values. Errors (%) resulting from the microbial contamination (calculated from the 15N values) in N-loss measurement with rapeseed, barley, ryegrass and barley straw, at 5, 12 and 24 h in 20 microns bags were respectively: -1.8, -3.9, -0.9; -3.8, -22.4, -3.8; -7.2, -4.1, -2.9; -164.5, -146.3, -204.6. In 40 microns bags the corresponding errors were respectively: -4.4, -1.2, -0.7; -26.1, -10.5, -3.9; -13.2, -6.4, -5.5; -221.2, -310.1, -1284.6.(ABSTRACT TRUNCATED AT 250 WORDS)

Retention time of chromium-labelled feed particles and of water in the gut of sheep given hay and concentrate at maintenance

Sheep were given a diet of 400 g chopped grass hay/d and 500 g crushed barley/d in three equal meals. The mean retention time in the whole gut (MRT) and the rumen retention time (RRT) of chromium-labelled feed particles and of water were estimated from marker concentrations in faecal samples. MRT of Cr-labelled hay (Cr-H), barley hulls (Cr-Bh), crushed peas (Pisum sativum) (Cr-CP) and rapeseed meal (Cr-RSM) were 53.5, 52.3, 44.3 and 37.0 h respectively when estimated from total faecal collections. The estimates obtained from spot samples of faeces were almost identical. RRT of Cr-H, Cr-Bh, Cr-CP, Cr-RSM (Expts 1, 2 and 3) and Cr-labelled cottonseed meal (Cr-CSM) was 35.9, 36.7, 25.3, 18.8, 19.8, 22.8 and 25.3 h respectively. The Cr-labelled feed particles showed marked variations in density in water (Dw). However, both MRT and RRT were closely related to Dw (r -0.88 and -0.95 respectively). Rumen outflow rates of Cr-RSM in individual animals were related to the rumen outflow rates of water (r 0.76).

In vitro function and in vivo viability of stored platelet concentrates. Effect of a secondary plasticizer component of PVC storage bags

Previous studies have shown that CL-2399 (Cutter) and PL-130 (Fenwal) polyvinyl chloride (PVC) plastic bags are unsatisfactory for storage of platelet concentrates (PC) at 22 degrees C. In an effort to explain the effects of plastic bags, the chemical make-up of CL-2399 and PL-130 PVC films was determined and compared with that of P1-146 (Fenwal) PVC, which is satisfactory for PC storage at 22 degrees C. The only significant difference between the three materials was the incorporation of tetrahydrofurfuryl oleate (THFO) as a secondary plasticizer in CL-2399 and PL-130. The response of platelets to aggregating agents, uptake of serotonin, recovery from hyptonic stress, and serotonin release during storage following storage in a modified CL-2399 plastic prepared without THFO and designated CL-3000 (Cutter) was equivalent to PL-146 and far superior to CL-2399. In vivo studies in two laboratories of platelets stored in CL-3000 bags showed satisfactory recovery (56 +/- 4.2% and 46.7 +/- 2.7%) and survival (6.4 +/- 0.4 days and 7.4 +/- 0.6 days). From these studies we conclude that the THFO secondary plasticizer component of PL-130 and CL-2399 is the cause of the poor platelet viability of platelets stored in these plastic bags. The mechanism of impairment is not known. The causative agent(s) may be degradation products of THFO (formed during manufacture of the PVC film) that are leached from the plastic into PC during storage.