Relationship between oxidant stress and milk productivity in dairy cows

An imbalance between formation and detoxification of oxygen radicals leads to oxidant stress that may increase in more intense oxidative metabolism caused by a high intake of metabolizable energy to provide metabolic intermediates for the milk synthesis and secretion. This hypothesis was tested using dairy cows and the concentration of hydroperoxides in lipids (LHP) extracted from circulative lipoprotein particles of low and very low density (LDL and VLDL/chylomicrons) as oxidant stress indicator. The particles were prepared by ultracentrifugation of serum obtained by coccygeal bleeding (13 cows, 1. parity, n=8 and 2. parity, n=5, lactation stage, 53 +/- 1.4 days post partum) and purified by precipitation. Concentrations of LHP-LDL/mg Lipoprotein correlated significantly with daily milk yield (r = 0.73, P = 0.004) or daily milk energy output (r = 0.77, P = 0.003) in contrast to LHP of VLDL/chylomicron particles. Thus, some evidence was obtained for an almost linear, positive relationship between milk productivity and oxidant stress occurring in LDL.     

Vitamin A excreted in the urine of canines is associated with a Tamm-Horsfall like protein

Under physiological conditions canines transport vitamin A in blood plasma primarily as retinyl esters bound to lipoproteins and excrete substantial amounts of vitamin A as retinol and retinyl esters with urine. In the aqueous environment of urine, the hydrophobic vitamin A has to be associated with a protein. This vitamin A-protein complex was purified to homogeneity, prepared by preparative ultracentrifugation (density 1.21 g/mL), native polyacrylamide gel electrophoresis (PAGE) and size exclusion chromatography. The vitamin A-protein complex has a high molecular mass of > 5,000 kDa under native conditions. SDS PAGE under reduced conditions revealed a single band with a molecular mass of about 100 kDa for the protein moiety. Peptides obtained after limited proteolysis with trypsin from the 100 kDa protein were characterised by MALDI-TOF mass spectrometry and showed amino acid sequence homology to the human Tamm-Horsfall Protein (THP). This was further confirmed by a positive immunoreaction of the isolated protein with crossreacting human THP antibodies. The localisation of THP in dog kidneys was determined by using immunohistology. The reaction was strong along the entire thick ascending limb ofthe Henle loop and distal convoluted tubule. Our data point to the possibility that THP functions as a novel carrier for vitamin A in the urine of canines.     

No detectable carotenoid concentrations in serum of llamas and alpacas

Carotenoids are lipid‐soluble pigments and important for a variety of physiological functions. They are major dietary vitamin A precursors and act as lipophilic antioxidants in a variety of tissues and are associated with important health benefits in humans and animals. All animals must acquire carotenoids from their diet, but to our knowledge, there are no studies investigating the intestinal carotenoid absorption and their blood concentrations in New World camelids. The present study aimed to assess the serum concentrations of selected carotenoids in llamas (n = 13) and alpacas (n = 27). Serum carotenoids as well as retinol (vitamin A) and α‐tocopherol (vitamin E) were determined by high‐performance liquid chromatography coupled with mass spectrometry and these were unable to detect any carotenoids (α‐ and β‐carotene, α‐ and β‐cryptoxanthin, lutein, zeaxanthin, lycopene) in the samples. The concentrations of retinol in alpacas (2.89 ± 1.13 μmol/l; mean ± SD) were higher (p = 0.024) than those found in llamas (2.05 ± 0.87 μmol/l); however, the concentrations of α‐tocopherol were not significantly (p = 0.166) different (llamas: 3.98 ± 1.83 μmol/l; alpacas: 4.95 ± 2.14 μmol/l). The results show that both llamas and alpacas are not able to absorb intact carotenoids, but efficiently convert provitamin A carotenoids to retinol.     

Effect of β‐Carotene Supply During Close‐up Dry Period on the Onset of First Postpartum Luteal Activity in Dairy Cows

The aim of this study was to examine the effect of β‐carotene supply during the close‐up dry period on the onset of first postpartum luteal activity in dairy cows. Twelve cows were supplied with 2000 mg of β‐carotene (20 g Rovimix^®β‐Carotene containing 10%β‐carotene; DSM Nutrition Japan K.K., Tokyo, Japan) by oral administration daily from day 21 before expected calving date to parturition. Fourteen cows (control) did not receive β‐carotene supplementation. Blood samples were obtained on days 21, 14 and 7 before expected calving date and on days 1, 7, 14, 21 postpartum. When the plasma progesterone concentration exceeded 1 ng/ml by day 21 postpartum, luteal activity was assumed to have been initiated. The result showed that serum β‐carotene concentrations in the β‐carotene cows were higher than in the control cows during the experimental period (p < 0.01). The number of cows with the onset of luteal activity by day 21 postpartum was 9/12 in the β‐carotene cows and 4/14 in the control cows (p < 0.05). Retinol, certain metabolic parameters and metabolic hormones concentrations did not differ between β‐carotene and control cows. In addition, serum retinol concentration in β‐carotene cows without luteal activity was lower than in β‐carotene cows with luteal activity (p < 0.05), and serum gamma‐glutamyl transpeptidase concentration in β‐carotene cows with luteal activity (p < 0.05) and control cows without luteal activity (p < 0.01) was higher than in control cows with luteal activity. In conclusion, β‐carotene supply during the close‐up dry period may support the onset of luteal activity during early lactation in dairy cows.     

Regression analyses of weather effects on the annual concentrations of nitrate in soil and groundwater

To control the groundwater pollution by NO₃^–, different monitoring programs have been carried out during more than a decade in drinking water catchments in Germany. The monitoring programs are based on agricultural and hydrological data. Atmospheric influences and irregularities of sampling complicate the interpretation of NO₃^– values in the soil and in the groundwater. To take such complications into account, NO₃^– time series from a drinking water catchment in Lower Saxony were analyzed by multiple regression. A strong correlation between the precipitation during the fall season and the NO₃^– content of the soil was found. The NO₃^– content of the soil is also influenced by the October temperature. While the raw data of NO₃^– content of the soil did not decrease significantly over time, a highly significant yearly decrease of about 3 kg N ha^–1 or 50 % from 1992 to 2002 was observed after atmospheric influences were taken into account. The variability due to precipitation was amplified by changing the date at which samples were taken. The NO₃^– concentration of the groundwater near the surface decreased yearly by about 10 mg l^–1 or 55 % from 1993 to 2001. Beside this decrease, influences of the October temperature and the sampling depth on the NO₃^– concentration of groundwater were identified. It is concluded that a multiple regression analysis is indispensable in interpreting soil and groundwater NO₃^– time series of restricted length.     

Effects of oral supplementation with β-carotene on concentrations of β-carotene, vitamin A and α-tocopherol in plasma, colostrum and milk of mares and plasma of their foals and on fertility in mares

In this study, effects of oral β-carotene supplementation to mares (β-carotene group: 1000 mg/day, n = 15; control group: n = 15) from 2 weeks before foaling until 6 weeks thereafter on concentrations of β-carotene, vitamin A and α-tocopherol in plasma, colostrum and milk and plasma of their foals were determined. In addition, effects on fertility were studied. Beta-carotene concentrations increased in plasma and colostrum of β-carotene-supplemented mares compared to control mares (p < 0.05). In mares of both groups, β-carotene concentrations were higher in colostrum than in milk (p < 0.05). In foals, β-carotene concentrations increased with colostrum uptake and were higher in foals born to supplemented mares (p < 0.05; control group: 0.0003 ± 0.0002 μg/ml on day 0, 0.008 ± 0.0023 μg/ml on day 1; β-carotene group: 0.0005 ± 0.0003 μg/ml on day 0, 0.048 ± 0.018 μg/ml on day 1). Concentrations of vitamin A and α-tocopherol were higher in colostrum than in milk (p < 0.05) but did not differ between groups. Concentration of α-tocopherol in plasma of mares decreased over time and in foals, increased markedly within 4 days after birth. All but one mare (control group) showed oestrus within 2 weeks post-partum. Occurrence of oestrus did not differ between groups. More mares of the control group (7/7 vs. 5/12 in the β-carotene group) became pregnant after being bred in first post-partum oestrus (p < 0.05). In conclusion, β-carotene supplementation to mares increased β-carotene concentrations in plasma, colostrum and milk of mares and plasma of their foals but had no positive effects on fertility.     

Effects of chronic renal disease on the transport of vitamin A in plasma and urine of dogs

OBJECTIVE: To determine plasma and urine concentrations of retinol, retinyl esters, retinol-binding protein (RBP), and Tamm-Horsfall protein (THP) in dogs with chronic renal disease (CRD). ANIMALS: 17 dogs with naturally developing CRD and 21 healthy control dogs. PROCEDURE: A diagnosis of CRD was established on the basis of clinical signs, plasma concentrations of creatinine and urea, and results of urinalysis. Concentrations of retinol and retinyl esters were measured by use of reverse-phase high-performance liquid chromatography. Concentrations of RBP and THP were measured by use of sensitive ELISA systems. RESULTS: Dogs with CRD had higher plasma concentrations of retinol, which were not paralleled by differences in plasma concentrations of RBP. Calculated ratio of urinary total vitamin A (sum of concentrations of retinol and retinyl esters to creatinine concentration) and ratio of the concentration of urinary retinyl esters to creatinine concentration did not differ between groups. However, we detected a significantly higher retinol-to-creatinine ratio in the urine of dogs with CRD, which was paralleled by a higher urinary RBP-to-creatinine ratio. Thus, in dogs with CRD, the estimated fractional clearance of total vitamin A, retinol, and RBP was increased. Furthermore, dogs with CRD had a reduced urinary THP-to-creatinine ratio. CONCLUSIONS AND CLINICAL RELEVANCE: Results of this study documented that CRD affects the concentrations of retinol in plasma and urine of dogs. Analysis of the data indicates that measurement of urinary RBP and urinary THP concentrations provides valuable information that can be helpful in follow-up monitoring of dogs with CRD.