Effect of dietary protein level and source on bone mineralization in rats.

Bone mineralization was studied in rats. Animals were divided into three feeding groups: LCP - diet with 13.5% crude protein in DM (5% of gluten, 10% of casein), HCP - diet with 21.2% CP in DM (8% of gluten, 10% of casein), and LSM - diet based on grain meals and meat-bone meal (21% CP in DM). After 28 days feeding, animals were euthanased by cervical dislocation and femur bones were collected, weighed and kept frozen until analyses. Diets with 21% protein (HCP, LSM) significantly increased weight of femur bones. Despite of the substantially higher ash level (7.1%) in the LSM diet than in the LCP diet (3.4%), rats of both groups had the similar bone concentration of Ca (15.7 +/- 1.1 vs. 17.4 +/- 1.1 g/kg) and Zn (178.7 +/- 7.9 vs. 173.0 +/- 8.5 mg/kg). However bone density in LSM rats was significantly higher than in LCP ones. Although rats fed HCP diet had intermediate bone density, the bone concentration of Ca (11.4 +/- 0.5 g/kg) and Zn (145.1 +/- 2.9 mg/kg) was significantly lower, than in animals fed LCP and LSM diets. This was related to the very wide protein/calcium (37:1 g/g) and protein/zinc (5.3:1 g/mg) ratios in HCP diet. Those ratios were narrowest in the LSM diet: 16.2:1 (CP/Ca) and 2.6:1 (CP/Zn). It can be conluded that protein/mineral ratio in a diet is a very important factor in bone development, besides dietary protein and ash contents itselves.

Rumen dry matter and crude protein degradability of extracted or untreated oilseeds and Leucaena leucocephala leaves.

A study was undertaken to determine the rumen DM and CP degradability characteristics of soyabean, canola seed, peanut, palm kernel and Leucaena leucocephala leaves. The oilseeds were either treated with n-hexane to extract the fat or left untreated. Nylon bags were incubated in each of four rumen cannulated sheep for 0, 2, 4, 6, 12, 24 and 48 h. Animals were fed on a diet consisting of meadow hay (ad libitum) and 150 g of concentrate twice daily. Fat extraction caused a decrease (P < or = 0.05) in DM disappearance of soyabean at 0, 2, 4, 6 and 12 h and of peanuts at all incubation times. CP disappearance from peanuts was reduced (P < or = 0.05) as a result of fat extraction at 0, 2, 4, 6 and 12 h. Fat extraction of canola seed increased CP disappearance at 0, 2, 4, 6 and 24 h (P < or = 0.05). However, in the case of defatted canola seed, an increase in DM disappearance (P < or = 0.05) was observed in the first 4 incubation times and a decrease (P < or = 0.05) in the later times. Fat extraction increased (P < or = 0.05) DM disappearance of palm kernel at 0 and 48 h, but reduced it at 4, 6 and 24 h. CP disappearance of palm kernel was improved by treatment (P < or = 0.05) at 0, 4, 24 and 48 h and decreased at 12 h. In the case of palm kernel the largest differences in DM and CP disappearance occurred between the 24 and 48 h incubation times. Degradability characteristics for DM and CP of full-fat soyabean, canola seed and peanut were comparable to those of the full fat samples. Effective DM degradability of soyabean, canola seed and peanuts was 72.2 and 71.9; 74.1 and 66.8; and 85.9 and 70.8 for full fat and extracted feeds, respectively. Effective CP degradability was similar in all oilseeds with the exception of the extracted canola seed. Therefore, the incorporation of full-fat soyabean, canola seed and peanut into ruminant rations can be considered as a means of increasing the energy balance. Both palm kernel DM and CP degradabilities were characterized by slow rates of degradation by negative values "b". This suggests the predominance of microbial colonization over disappearance during incubation. DM and CP disappearance of Leucaena leucocephala leaves originating from Cuba were lower than those from Nigeria. Degradability characteristics for CP and DM of Cuban leucaena leaves showed that the linear model resulted in a better fit than the exponential one.

Comparison of the influence of dietary fibre sources with different proportions of soluble and insoluble fibre on Ca, Mg, Fe, Zn, Mn and Cu apparent absorption in rats.

The 6 week experiment was performed on growing Wistar male rats. In the third and the sixth weeks digestibility trials were performed. The following high fibre preparations were supplemented to the control diet (C): high methoxylated citrus pectin (Cr); apple pomace (A), potato fiber "Povex" (P) and sugar beet pulp (B). Fibre supplementation, except Cr, significantly increased Ca, Mg, Fe, Mn, Zn, Cu excretion in faeces and decreased their apparent absorption in both trials. Significant correlations (P < or = 0.001) were found between crude, insoluble and total fibre intake and mineral excretion and apparent absorption. Apparent absorption of minerals increased from the third to the sixth week in group C and in group Cr, except Fe, while it decreased in groups P and B or showed tendency to decrease. In the sixth week the following differences (P < or = 0.05) in apparent absorption were observed between diets, in descending order: [equation: see text]

Determination of diaminopimelic acid in biological materials using high-performance liquid chromatography.

A method for the determination of diaminopimelic acid (DAPA) concentrations in feeds and rumen digesta by reversed-phase high-performance liquid chromatography using precolumn derivatization with o-phthaldialdehyde and fluorimetric detection was developed. Samples were oxidized and hydrolysed prior to analyses by HPLC. Hydrogen peroxide and formic acid were used for oxidation; hydrolyses were performed using 3 M hydrochloric acid under vacuum at 120 degrees C for 17 h. Oxidation allowed more space for DAPA-OPA peak elution and hydrochloric acid hydrolysis reduced sample clean-up and extended the column life. Hydrolysates were diluted, adjusted to pH 7 and filtered. A Beckman Model 507 autosampler with a precolumn derivatization cassette was used for the derivatization process and fluorimetric detection was used to measure the OPA derivatives. Samples were prepared in order to have on-column DAPA concentrations in the range 10-100 pmol. The relative recovery of the standard solutions added to the feed samples ranged from 98.4 to 102.8 %. The reproducibility of the method was evaluated by the analysis of eight alfalfa hay samples and eight alfalfa hay samples incubated in the rumen for 48 h and they yielded relative standard deviations of 2.04 % and 2.02%, respectively.