In vivo measurement of strontium absorption from the rumen of dairy cows as an index of calcium absorption capacity.

Absorption of dietary calcium from the rumen is a quantitatively important process in calcium homeostasis of ruminants. In 3 separate experiments in dairy cows, we applied a technique developed in sheep to measure the rate of strontium (Sr) absorption from the rumen as an indicator of calcium absorption capacity. Absorption from the rumen after an oral dose of SrCl2 resulted in a maximum plasma concentration of Sr after 1 h, whereas absorption from the small intestine after injection of SrCl2 into the abomasum through a cannula occurred more slowly. The second experiment demonstrated that the calcium absorption capacity index of the rumen was significantly greater in 21 lactating Friesian cows (230 ± 66, mean ± SEM) than in 6 mature, nonlactating, nonpregnant heifers (101 ± 21, mean ± SEM). In a third experiment, we compared clinically normal cows at the onset of lactation with those that developed parturient paresis. In cows that developed severe hypocalcemia, plasma concentrations of 1,25(OH)2D were significantly elevated (144 ± 60 pg/mL vs. 90 ± 54 pg/mL; means ± SEM) and their rumen calcium absorption index was significantly decreased compared with that of clinically normal cows. Evidence suggested that mobilization of calcium from bone as lactation commenced was significantly depressed in paretic cows compared with those that did not show clinical signs of hypocalcemia. Moreover, ruminal stasis suppressed the absorption of calcium from the rumen. We conclude that measurement of Sr concentration in blood plasma after an oral dose of SrCl2 into the rumen can be used as an index of rumen calcium absorption capacity under different states of calcium homeostasis.

Milk fever in dairy cows is preceded by activation of innate immunity and alterations in carbohydrate metabolism prior to disease occurrence.

The objective of this study was to search for potential alterations in innate immunity reactants and carbohydrate and lipid metabolism in the blood of transition dairy cows before, during, and after clinical occurrence of milk fever (MF) and identify potential predictive biomarkers of disease. One hundred pregnant multiparous Holstein dairy cows were involved in the study starting from -8wks before the expected day of parturition until +8wks postpartum as part of a large retrospective longitudinal study. Health status, DMI, milk yield, and milk composition were monitored during the whole experimental period. Six healthy cows (CON) and 6 cows that showed clinical signs of MF were selected for blood analyses. Serum concentrations of lactate, non-esterified fatty acids (NEFA), ß-hydroxybutyric acid (BHBA), interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor (TNF), haptoglobin (Hp), and serum amyloid A (SAA) were determined. Results indicated that concentrations of serum lactate, IL-6, TNF, SAA, and Hp were greater in cows with MF than those in the CON group at different time points. Moreover, serum lactate, TNF, SAA, and Hp were greater in cows with MF starting at -8 and -4wks prior to parturition. Both principal component analysis (PCA) and partial least squares - discriminant analysis (PLS-DA) showed separated clusters between MF and CON cows at -8, -4, and disease diagnosis weeks. Overall DMI and milk production were lower in MF-affected cows. Additionally milk fat and fat:protein ratio were greater in MF. In conclusion, cows affected by MF showed alterations in some of the innate immunity reactants and metabolites related to carbohydrate metabolism several weeks prior to appearance of clinical signs of MF. Variable importance in projection plots demonstrated that TNF and SAA in the serum were the strongest discriminators between MF cows and CON ones, which might be useful as predictive biomarkers of the disease.

[Evaluation of sulfur status in dairy cows in Germany]. / Untersuchungen zur Schwefelversorgung von Milchkühen in Deutschland.

OBJECTIVE: Sulfur deficiency and toxicity in livestock is associated with decreased performance and diseases. However, little is known about the diagnostics of sulfur status in dairy herds. The objectives of this study were to describe sulfur concentrations in feed rations in German dairy herds, to assess associations between feed sulfur concentrations and health and milk yield, to determine suitable laboratory diagnostic methods of sulfur status, and to propose reference values for the assessment of sulfur status in different sample media. MATERIALS AND METHODS: Between 2006 and 2014, a total of 569 dairy herds were visited. Blood, urine, and hair samples were obtained from 10 animals per group in the groups -3 to 0, 0 to 1, 3 to 5, and 15 to 18 weeks post partum (p. p.) (farms > 200 animals) or -3 to 0, 0 to 5, and 6 to 20 weeks p. p. (farms ≤ 200 animals). Pooled whole blood, serum, plasma, urine, and hair samples (n = 5663) were analyzed by ICP-OES. The sulfur content of the total mixed ration (TMR) of the group -3 to 0 weeks p. p. was determined in a certified feed laboratory (n = 625). Data analyses were performed using ANOVA, Chi-squared test and Spearman-correlation. Reference values were determined using the 2.5% and 97.5% percentiles. RESULTS: Median sulfur concentration in the feed rations was 2.3 g/kg dry matter (DM). Deficiency (< 1.6 g/kg DM; 31% of farms) and oversupply (> 4.0 g/kg DM; 11% of farms) of sulfur in feed rations were regularly diagnosed. Sulfur deficiency was associated with reduced milk yield (p  <   0.001), retained placenta (OR  =   1.74; p  =  0.037), milk fever (OR  =  2.68; p  <  0.001) and silent heat (OR  = 2.56; p   =  0.014). Positive correlations were found between sulfur concentration in feed rations and sulfur content in urine (r  =  0.50), serum (r  =  0.17), plasma (r  =  0.18) and whole blood (r = 0.16). Reference values for sulfur diagnostics in dairy herds were proposed. CONCLUSION AND CLINICAL RELEVANCE: Diagnostics of sulfur status in dairy herds is relevant for veterinary practitioners and can be performed using TMR analysis and clinical laboratory parameters. Urine can be considered a short-term parameter, serum, plasma, and whole blood as intermediate parameters, and hair as a long-term parameter for the evaluation of the sulfur status.

Calcium and magnesium physiology and nutrition in relation to the prevention of milk fever and tetany (dietary management of macrominerals in preventing disease).

Dairy cows may suffer events of hypocalcemia and hypomagnesemia, commonly known as milk fever and tetany. Milk fever is characterized by hypocalcemia at parturition as a consequence of a sudden increase in Ca demand and an unavoidable delay in Ca metabolism adaptation. Tetany is due to impaired Mg absorption from the rumen that cannot be compensated by absorptive or excretory adaptation, resulting in a net nutritional shortage of Mg and culminating in hypomagnesemia. Prevention strategies require triggering the activation of Ca gastrointestinal absorption and avoiding factors limiting ruminal Mg absorption.

Characterization of the serum metabolic profile of dairy cows with milk fever using 1H-NMR spectroscopy.

BACKGROUND: Milk fever (MF) is a common calcium metabolism disorder in perinatal cows. Currently, information regarding the detailed metabolism in cows suffering from MF is scant. OBJECTIVE: The purpose was to study the metabolic profiling of serum samples from cows with MF in comparison to control cows, and thereby exploring other underlying pathological mechanisms of this disease. ANIMALS AND METHODS: In the current study, we compared the serum metabolomic profile of dairy cows with MF (n = 8) to that of healthy dairy cows (n = 24) using a 500-MHz digital (1)H-nuclear magnetic resonance ((1)H-NMR) spectrometer. Based on their clinical presentation and serum calcium concentration, cows were assigned either to the control group (no MF symptoms and serum calcium concentration >2.5 mmol/L) or to the MF group (MF symptoms and serum calcium concentration <1.4 mmol/L). For statistical analysis, a one-way analysis of variance was performed. RESULTS: We identified differences regarding nine metabolites between the two groups, among which glucose, alanine, glycerol, phosphocreatine, and gamma-aminobutyrate decreased, and ß-hydroxybutyrate, acetone, pyruvate, and lysine increased in cows with MF. Most of these were carbohydrates and amino acids involved in various energy metabolism pathways. CONCLUSION: The different metabolites in cows with MF reflected the pathological features of negative energy balance and fat mobilization, suggesting that MF is associated with altered energy metabolism. CLINICAL IMPORTANCE: The (1)H-NMR spectroscopy can be used to understand the pathogenesis of MF and identify biomarkers of the disease.

Peripartal alterations of calcitonin gene-related peptide and minerals in dairy cows affected by milk fever.

BACKGROUND: Milk fever, a metabolic disease of dairy cattle, is associated with perturbations of calcium homeostasis, the pathogenesis of which is not yet completely understood. OBJECTIVE: The aim of this study was to investigate plasma concentrations of calcitonin gene-related peptide and selected minerals and metabolites in periparturient cows with and without milk fever. METHODS: Plasma concentrations of calcitonin gene-related peptide, as well as calcium, phosphate, magnesium, iron, glucose, lactate, and cortisol, were determined in multiple plasma samples from Jersey cows with and without spontaneous milk fever. RESULTS: Cows affected by milk fever (n = 5) had lower concentrations of calcitonin gene-related peptide (P = .038) and inorganic phosphate (P < .001) in plasma than did the controls (n = 5). Also, these cows tended to have lower calcium concentrations (P = .071). Magnesium, iron, lactate, glucose, and cortisol concentrations were comparable between both groups of cows (P > .10). Around the day of calving, plasma concentrations of lactate, glucose, and cortisol increased and the concentration of iron decreased in all cows (P ≤ .01). CONCLUSIONS: Despite the limited number of cows evaluated, this report is the first to indicate lowered concentrations of calcitonin gene-related peptide as part of the metabolic changes during milk fever in cows. Further work with a larger cohort of animals is warranted to understand the precise role of calcitonin gene-related peptide and the potential associations with disturbances in plasma minerals typically observed during milk fever.

Proteomic analysis of plasma from cows affected with milk fever using two-dimensional differential in-gel electrophoresis and mass spectrometry.

Milk fever is an important metabolic disorder of dairy cows after calving, and is characterized by hypocalcemia, tetany, lateral recumbency, and eventual coma. To date, there have been many reports about the pathogenesis and pathophysiology of milk fever, but the plasma protein profile in milk fever has not been reported. The aim of our study was to investigate novel pathophysiological changes in the plasma proteome of cows affected with milk fever. Plasma samples were collected from eight Holstein cows with milk fever (T), and eight control Holstein cows without milk fever (C), at an intensive Holstein dairy farm in Heilongjiang province, China. Samples were analyzed by fluorescence two-dimensional (2D) differential in-gel electrophoresis (DIGE), followed by in-gel digestion, and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) for peptide mass fingerprinting of selected protein spots. Eight of the 23 differential protein spots in the plasma of T and C cows were isolated and identified by 2D-DIGE and MALDI-TOF-MS. The protein spots represented five unique proteins, and had significant alterations in spot volume as determined by DeCyder differential in-gel analysis (DIA) software. The upregulated proteins were identified as serpin peptidase inhibitor (angiotensin), which regulates blood pressure and maintains fluid and electrolyte homeostasis, and endopin 2B which is involved in neural regulation. The downregulated proteins were serum albumin, which acts as a transport protein, fibrinogen beta chain which is involved in blood coagulation, and IgG heavy-chain C-region (IgG-C(H)) which participates in the immune response. In conclusion, we were able to use proteomic technologies to identify several novel plasma proteins in cows affected with milk fever. These findings may reveal new pathophysiological changes that occur in cows with milk fever.

Predicting timothy mineral concentrations, dietary cation-anion difference, and grass tetany index by near-infrared reflectance spectroscopy.

The mineral concentration of forage grasses plays a significant role in 2 metabolic disorders in dairy cattle production, namely, hypocalcemia (milk fever) and hypomagnesemia (grass tetany). Risks of occurrence of these 2 metabolic disorders can be evaluated by determining the dietary cation-anion difference (DCAD) and the grass tetany (GT) index of forages and specific rations. The objective of this study was to evaluate the feasibility of predicting timothy (Phleum pratense L.) mineral concentrations of Na, K, Ca, Mg, Cl, S, and P, the DCAD, and the GT index by near-infrared reflectance spectroscopy (NIRS). Timothy samples (n = 1,108) were scanned using NIRS and analyzed for the concentration of 7 mineral elements. Calculations of the DCAD were made using 3 different formulas, and the GT index was also calculated. Samples were divided into calibration (n = 240) and validation (n = 868) sets. The calibration, cross-validation, and prediction for mineral concentrations, the DCAD, and the GT index were performed using modified partial least squares regression. Concentrations of K, Ca, Mg, Cl, and P were successfully predicted with coefficients of determination of prediction (R(P)2) of 0.69 to 0.92 and coefficients of variation of prediction (CV(P)) ranging from 6.6 to 11.4%. The prediction of Na and S concentrations failed, with respective R(P)2 of 0.58 and 0.53 and CV(P) of 82.2 and 12.9%. The 3 calculated DCAD and the GT index were predicted successfully, with R(P)2 >0.90 and CV(P) <20%. Our results confirm the feasibility of using NIRS to predict K, Ca, Mg, and Cl concentrations, as well as the DCAD and the GT index, in timothy.

The effect of calcium-naloxone treatment on blood calcium, beta-endorphin, and acetylcholine in milk fever.

Milk fever is a postpartum syndrome of cows characterized by acute hypocalcemia, which reduces the release of acetylcholine (ACH), inducing flaccid paralysis and recumbency. Our aim was to evaluate the effect of calcium (Ca2+) combined with naloxone (Nx, an opioid antagonist; Ca2+-Nx) on plasma concentrations of ACH, beta-endorphin (betaE), and Ca2+ just before treatment (T0) and at 15, 30, and 90 min after treatment (T15, T30, and T90, respectively). Thirty cows were divided into 3 groups of 10 cows each. In group A1, cows affected by milk fever were treated (i.v.) with a combination of 0.2 mL/kg of body weight (BW) of Ca2+ borogluconate (20%) and 0.01 mg/kg of BW of Nx hydrochloride dihydrate. In group A2, cows affected by milk fever were treated (i.v.) with 2 mL/kg of BW of Ca2+ borogluconate (20%). In group C, healthy cows were treated (i.v.) with a combination of 0.2 mL/kg of BW of Ca2+ borogluconate (20%) and 0.01 mg/kg of BW of Nx hydrochloride dihydrate. Cows underwent treatments within 24 h of calving. Blood samples were collected at T0 and at T15, T30, and T90 for quantitative determination of ACH, betaE, and Ca2+. The cows in groups A1 and A2 recovered within a mean of 20 +/- 10 min, although 4 cows in group A2 underwent a relapse. Blood Ca2+ concentrations in group C increased slightly at T30 and at T90 (T30: 8.8 +/- 0.6 mg/dL; T90: 8.7 +/- 0.6 mg/dL) after treatment, whereas the response in groups affected by milk fever was similar, even though Ca2+ concentrations showed a sharp increase (A1: 8.9 +/- 0.8 mg/dL; A2: 6.0 +/- 0.7 mg/dL), particularly at T15 in group A1. Concentrations of betaE showed a similar pattern in groups A1 and C, with an increase at T15 (A1: 8.2 +/- 1.0 ng/mL; C: 2.7 +/- 0.4 ng/mL) and a subsequent decrease until T90 (A1: 1.4 +/- 0.3 ng/mL; C: 1.4 +/- 0.4 ng/mL), whereas betaE remained constant throughout in group A2. Concentrations of ACH in group A1 decreased significantly between T0 and T15, T30, and T90 (T0: 7.2 +/- 1.1 nmol/L; T15: 4.2 +/- 1.2 nmol/L; T30: 2.9 +/- 0.8 nmol/L; T90: 3.1 +/- 0.3 nmol/L), whereas in group A2, it did not change. In group C, concentrations of ACH decreased at T15 and increased again at T30 (T15: 1.1 +/- 0.3 nmol/L; T30: 3.2 +/- 0.7 nmol/L). Our results suggest that administration of Ca2+-Nx, which restored the physiological Ca2+ concentrations, might have an effect on nicotinic receptors by restoring the normal neuromuscular transmission at the motor endplate.

The role of dietary calcium concentration in the use of anionic salts to prevent parturient paresis in dairy cows.

The role of dietary calcium concentration during the feeding of anionic salts (AS) was reviewed. Hypocalcaemia is still the major cause of parturient paresis in dairy cows. Feeding AS is an established method for preventing severe hypocalcaemia by activating the calcium metabolism in the last two to three weeks before parturition by inducing a metabolic acidosis. In compensation for this acidosis, the organism increases the concentrations of ionised Ca [Ca2+] in the blood. This increase leads to an increasing excretion of calcium via the urine, which is ensued by an increased calcium absorption in the intestine. The ongoing metabolic acidosis changed the flux of Ca. The size of the Ca pool, however, remained unchanged. As the calcium metabolism is activated by AS, it seems necessary to increase the amount of calcium that is fed to the cows. Several studies examined the impact of different dietary calcium concentrations on the acid-base balance and the calcium metabolism in cows fed anionic salts. The study designs vary concerning the amounts of calcium fed and the use of pregnant or non-pregnant cows. Only one study combined the feeding of AS with a very low amount of calcium, which fell below the daily requirements of pregnant cows in the last three weeks before parturition. In this study, the calcium balance post partum was better in the cows that were administered AS and a high calcium diet. In the other studies, the amount of calcium in the different experimental groups and the difference between the amounts of calcium fed varied greatly. As far as it was monitored in the studies, the calcium concentration of the diet did not have a significant impact on the degree of acidosis induced by AS. In pregnant cows, no significant differences in the calcium concentration in serum or urine occurred before parturition. Some of the researchers found a lower incidence of parturient paresis when cows were fed a combination of AS and a higher amount of calcium, but some other researches did not. Interestingly, the parameters of bone metabolism did not change between experimental groups. According to what is currently known, the feeding of AS to transition cows should not be combined with a dietary calcium concentration that falls below the requirement of cows in this stage of lactation. On the other hand, there is no need to increase the Ca concentration. When AS are used the dietary calcium concentration should be between 9 g and 12 g/kg dry matter. Further research is needed to investigate the role of dietary calcium regarding the use of AS for improving Ca metabolism in dairy cows around parturition.

Biomarkers for the activation of calcium metabolism in dairy cows: elevation of tartrate-resistant acid phosphatase activity by lowering dietary cation-anion difference is associated with the prevention of milk fever.

In our previous study, it was demonstrated that the administration of anion salts, which slightly lower the dietary cation-anion difference (DCAD), in the prepartum period is safe and effective for preventing milk fever in multiparous cows. In the present study, several biomarkers, which might show activation of Ca metabolism, were analyzed using stored samples in the previous study to investigate the mechanism of the preventive effect on milk fever by lowering DCAD. Changes in bone-specific alkaline phosphatase activity, osteocalcin and insulin-like growth factor I concentrations in serum were almost the same among the three groups of multiparous cows with or without the oral administration of anion salts, while the levels of these serum biomarkers in the group of primiparous cows (heifer group) were much higher compared with those in the three multiparous groups throughout the experimental period. Urinary deoxypyridinoline excretion was not a useful biomarker for dairy cows because it hardly changed during the peripartum period in all groups. However, serum tartrate-resistant acid phosphatase (TRAP) activity, which is known as a biomarker of osteoclast activity, was well associated with the administration of anion salts lowering DCAD because among the three multiparous groups, only the group of multiparous cows fed the anion salts (anion group) showed an increased level, which rose to the level in the heifer group, and was markedly higher than those in the other control groups of multiparous cows. The increased activity of serum TRAP in the anion group suggested that Ca in the plasma pool was mobilized smoothly from bone-bound Ca via mature osteoclasts at parturition, which might be due to prior activation under mild acidosis induced by slightly lowering DCAD. Therefore, TRAP was the best biomarker to monitor the activation of Ca metabolism in dairy cows fed anion salts.

Preventive effect of mildly altering dietary cation-anion difference on milk fever in dairy cows.

In the present study, we examined whether mildly altering dietary cation-anion difference (DCAD) contributes to the prevention of milk fever in dairy cows. Thirty multiparous cows and ten primiparous cows (heifer group) were used in this study and the multiparous cows were randomly divided into three groups of ten animals each (anion, non-anion and control groups). The cows in the anion group were given supplemental salts that slightly lowered DCAD. These salts consisted of 115 g of CaCO3, 42 g of CaHPO4, 65 g of MgSO4 x 7 H2O and 80 g of CaCl2 x 2 H2O as a daily dose for each cow, using a catheter from 21 days before the expected date of parturition until parturition. The cows in the non-anion group were given only the same Ca, Mg and ip supplement but no sulfate and chloride salts as that in the anion group. The cows in the control and heifer groups were not given any additional supplement. The incidence of hypocalcemia in the anion group decreased to approximately half of those in the non-anion and control groups, while the heifer group did not develop hypocalcemia at all. In addition, the number of days spent for the treatment of hypocalcemia and the number of drug bottles (calcium borogluconate solution) used for the treatment decreased to less than half in the anion group compared with those in the non-anion and control groups. At parturition, the serum Ca concentration in the control (6.2 +/- 1.9 mg/dl, mean +/- standard deviation) and non-anion groups (6.4 +/- 1.7 mg/dl) were significantly lower than that in the heifer group (8.3 +/- 0.4 mg/dl), and the level in the anion group was intermediate (7.3 +/- 1.3 mg/dl). The change in ionized Ca concentration was almost the same as that in serum Ca concentration, but only the concentration in the anion group tended to increase slightly from a week before parturition and was significantly higher than that in all other groups three days before parturition. Urinary pH in the anion group was maintained at a mildly acidic level (6.8-7.0) for the last two weeks before parturition, compared with those in the control (7.3-7.5) and non-anion groups (7.9-8.1), and similar to that in the heifer group (6.3-7.3). The urinary Ca excretion was the highest in the anion group among all groups during the prepartum period. There were no specific changes in the excretion of parathyroid hormone and 1,25-dihydroxyvitamin D in all groups of multiparous cows while the levels of these hormones remained low in the heifer group throughout the experimental period. The data in the present study indicates that the administration of anion salts that slightly lowered DCAD in the preparum period was effective for preventing milk fever in multiparous cows. Safe and mild metabolic acidosis induced by the anion salts could be evaluated by urinary pH (6.8-7.0), and might increase the responsiveness to Ca requirement at parturition through some complex mechanisms unrelated to the excretion of Ca-related hormones. In addition, it was clarified that primiparous cows have a high potential to respond to sudden Ca demand unrelated to hormone excretion, and their Ca metabolism was in some respects similar to that in multiparous cows fed anion salts. Therefore, manipulating mildly DCAD is expected to be an effective, safe and natural method for preventing milk fever in dairy cows.

Use of pre-partum urine pH to predict the risk of milk fever in dairy cows.

The objective of this study was to evaluate the correlation between serum calcium (Ca) and inorganic phosphorus (IP) values and urine pH of cows fed common rations without the addition of anionic salts in late pregnancy. One hundred and seven Holstein cows, having completed two or more lactations and with an expected calving date within the next seven days were selected from two herds. In order to determine levels of serum Ca and IP and urine pH, blood and urine samples were collected seven to one days before parturition. Of the 107 sampled cows, 17 developed recumbency after calving and were considered to be affected by milk fever. There were significant ( p<0.01 ) negative correlations between urine pH and serum Ca, IP and the ratio of Ca to IP, The urine pH, and levels of serum Ca and IP measured within 48 h prior to parturition differed significantly ( p<0.001 ) between recumbent and non-recumbent cows. The sensitivity, specificity, positive and negative predictive values of urine pH test 48 h prior to parturition, using a cut off level of above pH 8.25, were 100%, 81%, 55%, and 100%, respectively. These signify that monitoring urine pH within 48 h prior to parturition is a sensitive method to assess the risk of parturient paresis. The results of this study emphasize the importance of acid-base status of the animal in the pathophysiology of milk fever.

Association between changes in plasma calcium concentration and plasma tartrate-resistant acid phosphatase activity in periparturient cows.

Eight periparturient Holstein Friesian cows were examined for plasma tartrate-resistant acid phosphatase (TRAP) activity to assess the degree of bone metabolic activity and to evaluate the association between the change in calcium (Ca) concentration and bone metabolism during the periparturient period. Milk fever occurred in 1 of 8 cows just after parturition. Plasma TRAP activities did not markedly change in 5 of 8 cows during the experimental period. The changing rate of Ca between preparturition and just after parturition was under -20% in 3 of 8 cows, and low TRAP activities were observed in 2 of these 3 cows. This study suggests that cows with a low TRAP activity are at risk of developing milk fever in comparison to cows with high TRAP activity. Temporary increases of parathyroid hormone were observed in 7 cows, but not in the cow with milk fever.

Serum activities of tartrate-resistant acid phosphatase and bone specific alkaline phosphatase as indices of bone metabolism in the cow.

The correlation between the serum hydroxyproline concentration and serum activity levels of TRAP and BALP was examined in 41 cows. The correlated coefficient (r) was 0.6391 for TRAP and 0.3147 for BALP, respectively. Judging from the significant correlation to the serum hydroxyproline concentration, serum TRAP activity is an index for bone metabolism in cows. Serum TRAP activity was therefore measured in 205 healthy cows (2-9 years old) in order to observe the changes in bone resorption with aging and milk production. TRAP levels differed slightly between group A (< or =4 yrs) and B (5 yrs< or =) at the same stage of lactation. The activity levels rose slightly at the height of lactation stage and during the dry stage.

Effect of mastectomy on milk fever, energy, and vitamins A, E, and beta-carotene status at parturition.

The objective of this study was to compare blood profiles of intact and mastectomized periparturient cows to discriminate those metabolic changes associated with the act of parturition from the metabolic changes caused by lactation. Mastectomized and intact cows had similar increases in plasma estrogens and cortisol concentrations around the time of calving. Mastectomy eliminated hypocalcemia and the rise in 9,13-di-cis retinoic acid observed in intact cows. Mastectomy reduced but did not eliminate decreases in plasma phosphorus, alpha-tocopherol, and beta-carotene associated with parturition in intact cows, suggesting the mammary gland is not the sole factor affecting plasma concentrations of these compounds. Dry matter intake was similar in both groups before calving. The day of calving, dry matter intake was lower in intact cows than in mastectomized cows, but after calving the mastectomized cows exhibited a pronounced decline in feed intake. Plasma nonesterified fatty acid (NEFA) concentrations rose rapidly in intact cows at calving and did not return to baseline level for > 10 d. In contrast, NEFA concentrations in mastectomized cow plasma rose moderately at calving and returned to baseline level 1 to 2 d after calving. This study provides evidence that hypocalcemia in the cow is solely a result of the calcium drain of lactation. The act of parturition affects blood phosphorus, dry matter intake, and NEFA concentration independent of the effect of lactation.

Relevance of apolipoproteins in the development of fatty liver and fatty liver-related peripartum diseases in dairy cows.

Most metabolic diseases in dairy cows occur during the peripartum period and are suggested to be derived from fatty liver initially developed during the nonlactating stage. Fatty liver is induced by hepatic uptake of nonesterified fatty acids that are released in excess by adipose tissues attributable to negative energy balance. The fatty accumulation leads to impairment of lipoprotein metabolism in the liver, and the impairment in turn influences other metabolic pathways in extrahepatic tissues such as the steroid hormone production by the corpus luteum. Detailed understanding of the impaired lipoprotein metabolism is crucial for elucidation of the mechanistic bases of the development of fatty liver and fatty liver-related peripartum diseases. This review summarizes results on evaluation of lipoprotein lipid and protein concentrations and enzyme activity in cows with fatty liver and those with ketosis, left displacement of the abomasum, milk fever, downer syndrome and retained placenta. Obtained data strongly suggest that decreases in serum concentrations of apolipoprotein B-100, apolipoprotein A-I and apolipoprotein C-III, a reduction in activity of lecithin:cholesterol acyltransferase and induction of haptoglobin and serum amyloid A are intimately related to the development of fatty liver and fatty liver-related diseases. Moreover, determination of the apolipoprotein concentrations and enzyme activity during the peripartum period is useful for early diagnoses of these diseases.

Effects of naloxone on calcium turnover in cows affected by milk fever.

Milk fever is a metabolic disorder of calcium homeostasis that affects about 2 to 6% of postpartum cows. Current therapy is based on the administration of calcium gluconate. On the basis of the clinical signs, and given that endorphins increase at parturition, we supposed that endogenous opioid peptides (EOP) could be responsible for this pathology. In this study, cows with milk fever were administered the opiate antagonist, Naloxone (Nx; experiment 1) or Nx with calcium salts (experiment 2). In experiment 1, Nx induced the recovery of affected cows. The effects of Nx therapy, expressed in terms of proportion of recovered cows, of cows recovering in less than 30 min and cows requiring repeated treatments, were not statistically different than those obtained by means of calcium administration (17/17, 100%; 10/17, 59% and 7/17, 41% vs. 33/35, 94%; 22/35, 63% and 11/35, 31%, respectively; NS). In experiment 2, a significantly higher ratio of cows recovered in less than 30 min in the group of animals treated with Nx in association with calcium salts, compared with the group of cows treated with the calcium traditional therapy (106/118, 90% for calcium-Nx treated cows vs. 34/62, 55% for calcium-treated cows). Moreover, in the group of cows treated with calcium-Nx, the number of cows requiring repeated treatments was significantly reduced and no unrecovered cows were observed. The results support the idea that high EOP levels interfere with inward movement of calcium through the cell membrane and with calcium activity. The association of calcium and Nx at low dosage is a safe method to treat milk fever in cows and reduces muscular complications.