Persisting hypocalcaemia in the cow--predisposing factors

Results from a clinical study involving 540 cows which recovered after one treatment for hypocalcaemia, 159 cows which recovered after two treatments for hypocalcaemia, and 61 cows which recovered after at least three treatments for hypocalcaemia, showed that the number of treatments before recovery was significantly related to the following factors: Plasma Ca, plasma Mg, packed cell volume, time of first treatment in relation to calving, season of the year, previous milk fever history, management system and the cow's body condition.     

The effect of dietary calcium and phosphorus supplementation in zeolite a treated dry cows on periparturient calcium and phosphorus homeostasis

Previous studies have proved the possibility of preventing parturient hypocalcaemia by zeolite A supplementation during the dry period, and a recent in vitro study has indicated a marked calcium (Ca) as well as phosphorus (P) binding effect of zeolite A in rumen fluid solutions. Because of the connection between the Ca and P homeostatic systems, the preventive effect against parturient hypocalcaemia may arise from zeolite induced decreased availability of dietary Ca as well as P. In the present study, the expected Ca and P binding capacity was challenged by feeding high and low levels of dietary Ca and/or P to zeolite A treated dry cows. Twenty-one pregnant dry cows were assigned to four experimental groups receiving a dry cow ration unsupplemented or supplemented with extra Ca and/or P. During the last 2 weeks of the dry period all cows additionally received 600 g of zeolite A per day. A high level of dietary P prepartum significantly decreased the plasma Ca concentration before as well as immediately after calving (day 0-3). Conversely, the plasma inorganic phosphate concentration was higher among these cows than among cows receiving no supplemental P. The prepartum dietary Ca level significantly affected the serum 1,25-dihydroxyvitamin D concentration during zeolite supplementation, whereas the periparturient plasma Ca concentration was apparently not affected by the dietary Ca level. During zeolite A supplementation plasma parathyroid hormone was significantly higher among cows receiving additional P. The urinary deoxypyridinoline/creatinine ratio was not affected by the prepartal dietary Ca or P level. Serum aluminium (Al) was significantly higher during zeolite A supplementation than during the preceding period, indicating partial destruction of the zeolite in the intestinal tract with subsequent release and absorption of Al. It is suggested that the effect of prepartum zeolite supplementation on the periparturient Ca homeostasis depends on the level of Ca as well as P in the dry cow ration.     

Oral 1,25-dihydroxyvitamin D3 in prevention of milk fever

The effect of daily oral doses of 1,25-dihydroxy vitamin D₃ (1,25-(OH)₂D₃) on plasma mineral concentrations and incidence of milk fever was tested in 39 aged cows. Three dose levels of 1,25-(OH)₂D₃ (0, 100 and 200 µg/d) were compared in cows supplemented with 100 g Ca/d (250 g CaCO₃) and in cows receiving no Ca supplement. 1,25-(OH)₂D₃ treatments were given from day 5 before expected calving (day –5) until the day after calving (Calving = day 0).Expected minima in Ca concentrations in plasma were seen on day 1 in placebo treated cows, while Ca concentrations in 1,25-(OH)₂D₃ treated cows were normal or increased in the period from start of treatment until day 3–5. In the parturient period (day –1 to +2) 1 of 21 treated cows developed milk fever, as compared to 4 of 18 untreated. A pronounced hypocalcaemia developed, however, in the 1,25-(OH)₂D₃ treated cows from day 3 to 5 onwards, culminating day 8–11 with 7 cases of milk fever. Ca supplements reduced the development of hypocalcaemia in the 1,25-(OH)₂D₃ treated cows, but could not completely prevent the occurrence of milk fever.     

Effects of a deficient magnesium supply during the dry period on bone turnover of dairy cows at parturition.

The bone activity and bone mineral content in rib bones resected from 33 dairy cows between 3 and 8 h after parturition were measured, and the effects upon them of a deficient supply of dietary magnesium (Mg) during the last seven weeks of pregnancy were studied. The cows were fed a diet containing either 0.22% magnesium (low Mg) or 0.82% magnesium (high Mg) in the dry matter (DM), and the potassium content of both rations was increased to approximately 4.1% in the DM to reduce the absorption of magnesium. In the cows fed the low-Mg diet a fall in plasma Mg concentration was observed. In the low-Mg, low-parity cows the plasma Mg concentrations at parturition were higher than in the low-Mg, high-parity cows, i.e. 0.83 mmol/l and 0.54 mmol/l, respectively. After parturition four cows in the low-Mg, high-parity group showed clinical signs of hypocalcaemia but none of the other groups did so. The bone formation in low-parity cows was significantly (P less than 0.05) affected by Mg supply, with higher percentages of both trabecular surface covered by osteoid and osteoid volume in the low-Mg group. In the high-parity cows no significant differences in bone formation were found between the low- and high-Mg groups. An inadequate Mg supply resulted in a significantly (P less than 0.05) higher Ca content in the bone ash of low-parity cows and a significantly (P less than 0.05) higher bone ash percentage in the bone of high-parity cows.     

泌乳奶牛低血钙的诊断和治疗

选择14头有运动障碍的荷斯坦泌乳牛,测定其血浆钙（Ca）、磷（P）含量,在日粮中添加石粉饲喂半个月后,再测定其血浆Ca、P。结果显示,患牛补充石粉前低血钙率达85.32%,补充石粉后15d降至16.67%,同时血浆Ca含量极显著升高（P〈0.01）,血浆P含量显著下降（P〈0.05）,钙磷比显著升高（P〈0.05）。因此,机体钙浓度低、磷浓度高所致的钙磷比失调是引起奶牛骨软症的主要原因。石粉能有效地防治奶牛骨软症。     

The Effect of Subclinical Hypocalcaemia Induced by Na2EDTA on the Feed Intake and Chewing Activity of Dairy Cows

The effects of induced subclinical hypocalcaemia (SCHC) on feed intake and chewing activity during eating and rumination were studied in dairy cows. Two non-lactating and non-pregnant cows were subjected to three different treatments, with one test per day, such that the plasma free (ionized) calcium (_FCa) concentration was maintained at the eucalcaemic level or at one of two constant SCHC levels. The cows and test days followed a 2×3 crossover design. SCHC was maintained for 7 h by repeatedly infusing 5% Na₂EDTA so that constant _FCa concentrations of 0.8 mmol/L or 0.6 mmol/L in plasma were achieved. Control conditions were achieved by infusing isotonic saline. Feed intake and the number of the rumination periods were recorded during test days. The proportion of feed eaten during each test meal (EatPro) was related to the mean plasma _FCa. An almost linear decrease in EatPro was observed when the plasma _FCa was 0.6–0.9 mmol/L. The cows showed no other clinical signs of hypocalcaemia during Na₂EDTA-infusion. The time spent chewing during eating and rumination, and the number of rumination periods during a test day, decreased with a decline in plasma _FCa concentration.It was concluded that induced SCHC depresses the feed intake and ruminative activity of dairy cows.     

Effect of pre-calving zeolite, magnesium and phosphorus supplementation on periparturient serum mineral concentrations

The objective of this study was to test whether supplementing dry cow rations with phosphorus (P) and magnesium (Mg) would interfere with the beneficial effect of zeolite supplementation on the periparturient blood calcium (Ca) concentration in dairy cattle. Three groups (A-C) of 10 Danish Jersey cows were each given the following daily supplements from 2 weeks before the expected date of calving until actual calving: group A: zeolite, monoammonium phosphate, standard dry cow mineral and vitamin mix, containing 61g magnesium phosphate; group B: zeolite, standard mineral and vitamin mix without the magnesium phosphate and group C: standard mineral and vitamin mix, monoammonium phosphate. All cows in group B had an apparently less variable serum calcium concentration around calving with no cases of milk fever and no subclinical hypocalcaemia or hypomagnesaemia recorded. In contrast, a parturient drop in blood Ca was seen in group A as well as group C. In group A, one cow was hypocalcaemic at calving, and developed milk fever. In group C, 12 blood samples, representing six cows, were hypocalcaemic, and three of these cows were treated for milk fever. All groups remained normomagnesaemic and there were no significant differences in blood Mg across groups. In conclusion, the combined P and Mg supplementation in addition to zeolite supplementation did not increase the serum Mg level (forage Mg 16.9g/day; 0.21% of DM). Combined P and Mg supplementation reduced the zeolite-induced hypophosphataemia but also reduced the stabilising effect of zeolite on parturient serum Ca.     

Blood pathophysiological changes in sheep following a prolonged (18-hour) period of hypocalcaemia induced by Na2EDTA solution.

Six aged Merino ewes were used in an experiment in which five were infused with 4.7% Na2EDTA solution intravenously for 18 h at a rate designed to produce hypocalcaemia and maintain recumbency, and five with 0.9% sodium chloride solution at the same rate for the same period (four were infused at different times with both solutions). Blood samples were collected every 3 h and determinations made of plasma Ca, Na, K, Mg, and inorganic P (PiP), erythrocyte Na, K and Mg, and PCV. Three of the hypocalcaemic sheep took 36-64 h to regain their feet. Plasma Ca and K, and erythrocyte Na showed significant (all P less than 0.01) decreases in the group infused with Na2EDTA compared with the group infused with saline while PCVs were significantly (P less than 0.01) greater in the former group. The sheep model used could be suitable for the study of the effects of prolonged hypocalcaemia and recumbency in cows.     

阴离子饲料添加剂"1号"对围产期奶牛血浆中钙镁磷的影响

为了预防围产期奶牛代谢性疾病的发生,了解试验牛体内钙、磷、镁的变化规律,选择20头围产期奶牛,添加研制的"1号"奶牛阴离子饲料添加剂,检测了分娩前、分娩日和分娩后试验奶牛血浆中钙、镁、磷的含量及新鲜尿液的pH.结果表明,血浆中钙分娩前,试验组与对照组差异显著(P＜0.05);镁离子总体比较,试验组与对照组差异极显著(P＜0.001);分娩前、分娩后试验组与对照组差异显著(P＜0.05).尿液pH在5.5～6.5之间.试验牛产后无瘫痪等疾病发生.     

Effect of diets containing sulfate or chloride-based anionic salts,fed to grazing prepartum dairy cows,on concentrations of Ca in plasma,disease incidence and milk yield

AIMS: To compare the effect of two partial mixed ration diets containing either sulfate or chloride-based anionic salts, fed to grazing prepartum dairy cows, on concentrations of Ca, Mg, P and beta-hydroxybutyrate (BHB) in plasma, disease incidence and milk yield during the early postpartum period.

METHODS: The study was conducted on a seasonal-calving grazing dairy farm located in Benton (MO, USA). In August 2016, two groups of 200 cows were randomly assigned at 30 days before expected parturition to receive either a sulfate or chloride-based anionic diet, to achieve a dietary cation–anion difference (DCAD) of ?25?mEq/kg DM. Cows were fed partial mixed rations to provide 50% of their DM intake, with 50% provided by grazing fescue pasture. Urine samples were collected from 20 cows from each group once a week for 5 weeks until calving for pH assessment. At parturition, 42 cows per group were selected at random and blood samples collected on Days 1, 2, 3 and 7 postpartum. The study continued until 100 cows per group calved. Health events and cumulative milk yield until 30 days postpartum were recorded. Concentrations of Ca, P, and Mg in plasma at Days 1, 2, 3, and 7, and BHB in plasma at Day 7 postpartum were assessed.

RESULTS: Mean urine pH was lower in cows in the chloride than sulfate group (p≤0.06) on four of five sampling occasions. Mean concentrations of Ca in plasma on Day 1 were 2.00 (95% CI=1.94–2.05) and 1.91 (95% CI=1.88–1.97) mmol/L for the chloride and sulfate groups, respectively (p=0.15), and on Day 3 were 2.03 (95% CI=1.97–2.08) and 1.90 (95% CI=1.84–1.96) mmol/L, respectively (p=0.038). Concentrations of Mg, P and BHB in plasma and incidence of diseases postpartum were similar in both groups (p>0.05). There were no cases of clinical hypocalcaemia in either group.

CONCLUSIONS AND CLINICAL RELEVANCE: Prepartum cows fed a partial mixed ration with a negative DCAD containing chloride-based anionic salts and free access to a fescue pasture had lower prepartum urine pH, and higher concentrations of total Ca in plasma during the first week postpartum, than cows receiving a partial mixed ration containing sulfate-based anionic salts.     

Effect of several doses of zeolite A on feed intake,energy metabolism and on mineral metabolism in dairy cows around calving

The object of the present study was to determine the influence of different zeolite A doses on dry matter intake (DMI) and mineral metabolism, and to evaluate an optimum dosage for preventing hypocalcaemia. Eighty pregnant dry cows were assigned to four groups (I–IV). They were fed a total mixed ration (TMR) ad libitum. Groups II, III and IV received an average daily dose of 12, 23 and 43 g zeolite A/kg DM for the last 2 weeks prepartum. Individually DMI was recorded daily. Blood and urine samples were taken before, during and after zeolite A supplementation. Serum was analysed for Ca, Mg, P_i, K, non‐esterified fatty acids and β‐hydroxybutyrate (BHB). Urine was analysed for Ca, Mg, P_i, K and net acid‐base excretion (NABE). After calving, milk yield (fat corrected milk) and milk composition were determined. During zeolite A supplementation, mean DMI of Group IV (7.3 ± 1.3 kg/cow/day) was significantly lower compared to Groups I–III (10.1, 10.9, 9.5 kg/cow/day). The reduced feed intake of Group IV resulted in significantly increased BHB as well as decreased NABE after calving. Zeolite A supplementation in higher doses (III and IV) had a stabilizing effect on Ca metabolism around calving for older cows, whereas cows in Groups I and II showed a subclinical hypocalcaemia. The mean serum Mg concentration decreased significantly in older cows in Group IV at calving. The mean P_i concentration in cows of Group IV decreased into ranges of hypophosphataemia already 1 week after beginning of zeolite A feeding. The mean DMI postpartum as well as the milk yield was not affected by zeolite A supplementation. Feeding of 23 g zeolite A/kg DM TMR prepartum proved to be an adequate dosage for reducing subclinical hypocalcaemia frequency without significant effects on feed intake and P_i concentration in serum.     

Variations in the response of sheep to experimental magnesium deficiency.

Hypomagnesaemia was induced in adult sheep by changing their diet from chaff given orally to a milk diet, low in Mg, infused via the abomasum. All sheep given the milk diet developed hypomagnesaemia and four out of 19 developed nervous convulsions similar to the natural disease grass tetany. Analysis of the sequential changes in plasma Ca, P and Mg revealed a striking positive correlation between Ca and Mg and hypocalcaemia thus appeared to be a general response to Mg deficiency. Many sheep appeared to adapt to the deficiency since after a period of about 11 days the decline in plasma Mg (and Ca) was either alleviated or reversed. However the four sheep which developed convulsions all showed a rapid and substantial decline in plasma Mg associated with a decline in plasma Ca.     

Effect of oral calcium bolus administration on milk production,concentrations of minerals and metabolites in serum,early-lactation health status,and reproductive performance of Holstein dairy cows

AIMS: To determine the effects of oral Ca bolus administration in the early postpartum period of cows on milk yield and composition, blood metabolites, early-lactation health status, and reproductive performance.

METHODS: Multiparous Holstein dry cows (n=66) with a mean parity of 3.1 (SD 0.35) were fed a diet with a positive dietary cation–anion difference (DCAD) prior to calving. They were randomly assigned to receive no treatment (Control; n=33) or two oral Ca boluses (n=33, 45?g of Ca per bolus); one was administered immediately after calving (Day 0) and the second 24 hours (±30 minutes) later. Blood samples were collected at calving, and on Days 2 and 7 to determine concentrations in serum of Ca, P, Mg, glucose, non-esterified fatty acids (NEFA), and β-hydroxybutyric acid (BHBA). Milk yield was recorded daily and milk composition was determined weekly from calving until 28 day postpartum. Health and outcomes were determined during the first 30 days postpartum and reproductive outcomes to 180 days postpartum.

RESULTS: Mean milk yields and composition over the first month of lactation were similar between cows in the two treatment groups (p>0.1). Mean concentrations of Ca in serum were not different between treatment groups on Day 0, but were higher on Day 2 for cows that received oral Ca boluses (1.77 (SE 0.07)) compared with Control cows (1.54 (SE 0.08)) (p=0.04). Concentrations in serum of P, Mg, glucose, NEFA and ΒHBA did not differ between treatment groups on any day of measurement. Fewer cows that received oral Ca were diagnosed with hypocalcaemia (total concentrations of Ca in serum <1.5?mmol/L) by Day 2 (2/33; 6%) compared with Control cows (12/33; 36%) (p=0.01). There was no difference in the prevalence of other health outcomes between treatment groups. The proportion of cows conceiving to first insemination was greater in cows that received an oral Ca bolus (19/29; 65%) than Control cows (12/29; 41%) (p=0.01).

CONCLUSIONS: Oral Ca bolus administration increased concentrations of Ca in serum on Day 2 postpartum, and increased first service conception rates, in cows fed a diet with a positive DCAD prior to calving compared to cows that received no oral Ca bolus supplementation. Because of the small number of cows used in this study, further studies in large-scale dairy farms should be carried out to confirm these findings.     

奶牛蹄叶炎与血浆中矿物元素含量的相关性分析

采集15头健康奶牛和36头蹄叶炎患病奶牛血浆样品,检测其Fe、Zn、Cu微量元素和Mg、Ca、P常量元素的含量及钙磷比,结果表明：2组间Fe、Cu、Mg、Ca和P矿物元素含量及钙磷比无显著性差异（P〉0.05）,患病牛Zn含量却显著低于健康牛（P〈0.05）。因此,奶牛血浆中Zn含量与蹄叶炎发病显著相关,Zn含量可能会作为蹄叶炎发病的监测指标,也可用于奶牛蹄叶炎的早期诊断和防治。     

Urinary calcium excretion in non‐lactating dairy cows in relation to intake of fat‐coated rice bran

At calving, many older cows fail to compensate the sudden demand of calcium by an adequate activation of intestinal absorption. This results in a variable degree of hypocalcaemia. Reducing intestinal availability of calcium during the close‐up period can prevent milk fever. Fat‐coated rice bran (FCRB) was investigated for its potential to reduce Ca availability in pre‐calving cows. Fat‐coated rice bran was incubated in situ to estimate ruminal degradation of dry matter and phytic acid. Also, seven dry multiparous dairy cows were used for a feeding trial in three periods of approximately 1 week each: P1: adaptation; P2: feeding of 2 kg of FCRB and P3: withdrawal of FCRB. Feed intake was recorded and daily urine samples were analysed for pH, Ca and creatinine. The bypass fraction of phytic acid (passage rate: 5%/h) was 30%. Fat‐coated rice bran depressed dry matter intake in P2, resulting in a lower Ca intake. In P2 urine pH and calcium excretion were lower. Daily calcium excretion decreased after introduction of FCRB, peaked after withdrawal and dropped 2 days later. Changes in urinary Ca excretion by feeding FCRB indicate that FCRB affected Ca homeostasis in dry multiparous dairy cows.     

过瘤胃维生素D对围产期奶牛低血钙症的影响

为了阐明日粮添加过瘤胃维生素D对围产期奶牛低钙血症的调控机制,在某集约化奶牛场选取40头奶牛,随机分为4组,对照组(C)饲喂基础日粮,试验Ⅰ、Ⅱ、Ⅲ组分别于产前10d至分娩后10d在日粮中每天添加1.5、3.0、6.0g/头过瘤胃维生素D。对4组试验奶牛围产期(分别于产前10、7、3、0d和产后3、7、10d)血清维生素D3(1,25-(OH)2D3)、钙、羟脯氨酸、甲状旁腺素和降钙素水平进行检测。结果表明,围产期奶牛血钙水平分娩时达最低,产后逐渐上升,且产前7d至产后10d对照组奶牛血钙浓度显著低于试验Ⅰ组(P<0.05);分娩当天试验Ⅰ组奶牛血浆中1,25-(OH)2D3、羟脯氨酸和降钙素水平显著高于对照组(P<0.05),甲状旁腺素水平显著低于对照组(P<0.05)。提示,日粮中每天添加1.5g/头过瘤胃维生素D能调节甲状旁腺素和降钙素等激素的分泌,促进肠道对钙的吸收,动员骨钙,从而防止奶牛产后低钙血的发生,且围产期奶牛低血钙症与机体血钙稳态调节作用密切关联。     

Effects of low and high calcium intake prepartum on calcium mobilization rate around parturition in dairy cows

Forty-one dairy cows were fed a low (LCa-13 g/d) and a high (HCa-83.5 g/d) calcium ration in the 8 weeks prior to parturition and the effect on the Ca mobilization rate around parturition was studied. Plasma Ca values were stable in the LCa group around parturition. In the older cows of the HCa group a very slight decrease in the mean plasma Ca was observed: 2.58 mmol/l at 12-36 h ante partum decreased to 2.38 mmol/l at parturition. Hypocalcaemia, which commonly occurs around parturition, did not occur in 40 of the cows. A subclinical hypocalcaemia (1.8 mmol/l) occurred in one cow (parity 10) from the HCa group. To assess the efficiency of Ca mobilization, a severe hypocalcaemia (1.0 mmol/l) with clinical signs was induced by means of Na2EDTA infusion (0.90 mmol/min), starting at 10 h post-partum. The older cows in the LCa group required more Na2EDTA than those in the HCa group. Higher urinary hydroxyproline excretion in the week before parturition in the LCa than in the HCa group suggested a higher bone turnover. Plasma PTH levels around parturition were not significantly different between the groups. The amount of colostrum milked out in the first 10 h post-partum did not influence Ca homeostasis around parturition. The results contradict those of many other experiments in which hypocalcaemia was observed in cows ingesting high levels of Ca. It is concluded that the restricted feed intake prepartum possibly had a favourable effect on Ca homeostasis.     

Plasma Levels of Immunoreactive Parathyroid Hormone in Relation to Starvation Hypocalgaemia in Dairy Cows

The hypocalcaemia caused by parturition and onset of lactation in high-production dairy cows was mimicked by subjecting cows to starvation periods before and after partus. The changes in plasma calcium, phosphate and magnesium were followed and compared with immunoreactive parathyroid hormone (iPTH) in 2 cows. During the starvation periods before partus, the cows developed hypocalcaemia with no or only small changes in the plasma concentration of magnesium. After the onset of hypocalcaemia, the concentration of iPTH increased on the average 3–4-fold and the raised hormone levels lasted about 24 h after start of refeeding. An increase in plasma phosphate occurred somewhat later than the rise in iPTH and lasted longer. After partus hypocalcaemia developed, together with smaller increases in iPTH concentration (about 2-fold). The post-partum starvation period again resulted in hypocalcaemia and raised iPTH concentrations.In conclusion, starvation and parturition induced inverse changes in plasma calcium and iPTH in dairy cows. The increases in plasma iPTH were reversible and considered secondary to the hypocalcaemia. Through the effect of paratyroid hormone, plasma calcium was normalized and phosphate concentration increased. Therefore, fatal hypocalcaemia which may occur following the course of parturition and onset of lactation is not due to impaired PTH secretion.     

Labile magnesium reserves in beef cows subjected to different prepasture supplementation regimens

Thirty pregnant beef cows were utilized to determine the effects of winter Mg supplementation regimen on blood minerals after cows were turned to a spring tetanigenic tall fescue pasture. The winter Mg treatments were (1) tall fescue hay with free access to a Mg-deficient salt-mineral mix, (2) 6.4 kg of corn silage dry matter plus 114 g MgO/d and (3) tall fescue hay with free access to a salt-mineral mix containing 40% MgO from January 1 to February 15. All cows were then placed on the same tetanigenic pasture from February 15 to April 17 with free access to a Mg-deficient salt-mineral supplement. Forage Mg remained below .2% during the experiment. Forage Ca, P and Al changed throughout the spring, attaining maximum values of .35%, .46% and 415 ppm, respectively. Forage N and K also increased throughout the spring, reaching values of 3.5 and 3.8%, respectively, at the April 3 sampling. The forage K:(Ca + Mg) ratio approached 2.2 by March 26, which coincided closely with the average tetany date (March 29). Serum Mg averaged 1.97, 3.58 and 2.06 mg/dl for treatments 1, 2 and 3, respectively, on February 15 before turning cows to pasture. There were no treatment differences for serum Ca, P and K during the experiment. Eight cows exhibited symptoms of grass tetany (collapse) on an average date of March 29. Winter Mg supplementation provided little long-term protection against hypomagnesemia after turning cows to tetanigenic pasture, indicating that cows must have a supplemental source of Mg during this critical period.     

Protein expression in dairy cows with and without subclinical hypocalcaemia

AIM: To determine differences in plasma proteomic profiles between healthy cows and those with subclinical hypocalcaemia within 12 hours after calving, and thereby explore the underlying biological mechanism of subclinical hypocalcaemia in dairy cows.

METHODS: Plasma samples were collected within 6 hours of calving from Holstein cows on a farm in Heilongjiang, China; 32 with subclinical hypocalcaemia (plasma calcium concentration 1.38–2.00?mmol/L and no clinical signs) and 59 control cows (plasma calcium concentration 2.10–2.8?mmol/L). Plasma samples were applied to weak cationic exchange protein chips for protein profiling by surface-enhanced laser desorption/ionisation time-of-flight mass spectrometry (SELDI-TOF-MS), and the data were analysed using the PBS-IIC system. The amplitude of peaks for the two groups were compared using the Wilcoxon sum-rank test, and the mass-to-charge ratio of the peaks that differed was used to identify peptide fragments using the Swiss-Prot protein database.

RESULTS: Seven peaks were identified in the subclinical hypocalcaemia group that differed from those of the control group (p<0.001), that represented six unique proteins. Expression of serum albumin, fibrinogen alpha chain, amyloid beta A4 proteins and neurosecretory protein VGF were increased, and expression of apolipoprotein A-II and serum amyloid A proteins were decreased in the subclinical hypocalcaemic cows compared with control cows.

CONCLUSION: Use of SELDI-TOF-MS technology can effectively identify differences in plasma protein expression patterns in cows with subclinical hypocalcaemia. Neurosecretory protein VGF and amyloid beta A4 protein might represent useful biomarkers for diagnosis of subclinical hypocalcaemia.