Subclinical Hypocalcemia Research Articles

Neutrophil β-defensin gene expression of postpartum dairy cows is altered by prepartum dietary cation-anion difference

The objective of this study was to evaluate expression of a cluster of genes encoding β-defensin antimicrobial peptides in neutrophils of postpartum cows in relation to prepartum dietary cation-anion difference (DCAD), vitamin D, and postpartum disease. Pregnant dry Holstein cows (28 nulliparous and 51 parous) at 255 d gestation were blocked by parity and randomly assigned to 4 prepartum diets of positive (+130 mEq/kg) or negative (-130 mEq/kg) DCAD and either 3 mg vitamin D3 or 3 mg of 25-hydroxyvitamin D3 per 11 kg of dry matter/d. Treatment diets were fed from 255 d of gestation until calving. Peripheral blood neutrophils of 35 parous cows were collected at 0 and 3 d after calving and stimulated with 0 or 100 ng/mL of lipopolysaccharide (LPS). Furthermore, serum Ca and incidences of postpartum diseases were recorded for all cows. The mRNA transcripts of β-defensin genes were quantified by real-time PCR, and data were analyzed with a general linear mixed model to test for fixed effects and interactions of day, level of DCAD, source of vitamin D, and incidence of disease. Effects of DCAD and vitamin D on neutrophil oxidative burst and phagocytosis were previously reported but were analyzed for effects of disease in the present study. Transcripts for DEFB1, DEFB3, DEFB4, DEFB5, DEFB7, DEFB10, and lingual antimicrobial peptide (LAP) in neutrophils were upregulated by LPS at 0 d but not at 3 d. Transcripts for DEFB4 and DEFB7 in LPS-stimulated neutrophils were greater in cows fed negative DCAD diets compared with positive DCAD. Source of vitamin D (vitamin D3 vs. 25-hydroxyvitamin D3) did not affect expression of β-defensins in neutrophils. Cows with postpartum subclinical hypocalcemia (serum Ca <2.0 mM) had decreased DEFB3, DEFB4, DEFB6, DEFB7, DEFB10, and LAP expression in LPS-stimulated neutrophils compared with cows that did not experience subclinical hypocalcemia. Likewise, DEFB4, DEFB6, DEFB7, DEFB10, and LAP in LPS-stimulated neutrophils at 3 d postpartum were positively associated with serum Ca at 0 d postpartum. Transcripts for DEFB7, DEFB10 and LAP also were less abundant in neutrophils from cows with metritis compared with healthy cows. In conclusion, feeding a prepartum negative DCAD to improve postpartum serum Ca resulted in greater neutrophil β-defensin expression, and greater neutrophil β-defensin expression was positively associated with postpartum health.

Effect of storage time and temperature on total calcium concentrations in bovine blood

Subclinical hypocalcemia (SCH), a reduction in blood calcium concentrations without apparent clinical signs of milk fever, occurs in 25 to 50 % of early-postpartum dairy cows. Compared to their normocalcemic counterparts, these cows have an increased risk of subsequent disease developments, reduced milk production, and poorer reproductive performance. Due to the absence of an economical and accurate on-farm test, the mainstay of individual cow testing and herd-level monitoring is done through total calcium (tCa) analysis performed at regional laboratories or veterinary clinics. Due to practicality reasons, this often results refrigeration of whole blood for various lengths of time prior to centrifugation or prolonged storage of frozen plasma or serum. In order to provide bovine practitioners and researchers with the optimal method of handling samples for tCa testing, our objective was to examine the effect of storage time and temperature on tCa concentrations in bovine blood.

Effect of postpartum milking strategy on plasma calcium concentration and risk of subclinical hypocalcemia in dairy cows

Subclinical hypocalcemia affects most of multiparous dairy cows within the first 48 h after parturition. Most likely increased Ca requirements for colostrum synthesis at lactation onset drive the decrease in blood Ca concentration observed around parturition. The aim of the present study was to evaluate the effect of different postpartum milking strategies on plasma Ca concentration and risk of subclinical hypocalcemia in multiparous dairy cows.

Transient vs persistent subclinical hypocalcemia

Decreased blood calcium (Ca) concentration in the early postpartum period, often diagnosed as subclinical hypocalcemia (SCH), is a common occurrence in Holstein cows. Our objectives were to evaluate the association of SCH duration with the risk of early lactation negative events and milk production.

Randomized clinical trial assessing the effect of 3 different commercial oral calcium supplementation bolus on calcium dynamics and urine pH after calving

Calcium (Ca) homeostasis is one of the many metabolic challenges faced by a dairy cow during her transition from the dry period into lactation. The use of anionic salts during the dry period is an effective strategy to prevent clinical hypocalcemia, yet subclinical hypocalcemia (SCH) has been reported to affect up to 70% of multiparous cows. Although the use of oral calcium supplements immediately after calving is a commonly adopted method to prevent and treat SCH in multiparous cows, there is a shortage of information comparing different oral calcium products. Thus, the overall goal of this project is to evaluate the effect of different commercially available oral calcium products on postpartum serum calcium profiles of dairy cows. Additional objectives are: determine milk production, urine pH, and Ca concentrations during the first 5 days after oral calcium supplementation. This study is ongoing, with serum and urine samples currently being analyzed to determine Ca concentrations.

Effects of ORAI calcium release-activated calcium modulator 1 (ORAI1) on neutrophil activity in dairy cows with subclinical hypocalcemia1.

Hypocalcemia in dairy cows is often associated with inflammation-related disorders such as metritis and mastitis. The protein encoded by the Ca2+ release-activated calcium modulator 1 (ORAI1) gene is a membrane Ca2+ channel subunit that is activated when Ca2+ stores are depleted. Polymorphonuclear neutrophils (PMNL) have a crucial role in the defense against infection through migration, adhesion, chemotaxis, phagocytosis, and reactive oxygen species (ROS) production in response to pathogens. Whether hypocalcemia affects the activity of PMNL and if ORAI1 is involved remains unknown. To address this, PMNL were isolated at 3 d of calving from dairy cows diagnosed as clinically healthy (n = 20, CONTROL) or with plasma concentration of calcium < 2.0 mmol/L as a criterion for diagnosis of subclinical hypocalcemia (n = 20, HYPOCAL). PMNL isolated from both groups of cows were treated with or without the sarcoendoplasmic Ca2+ ATPase inhibitor thapsigargin, Ca2+ ionophore Ionomycin, and ORAI1 blocker 2APB. The intracellular Ca2+ concentration, ORAI1 abundance, ROS, phagocytosis rate, migration, and adhering capacity of treated PMNL were evaluated. Some of the in vitro assays also included use of small interfering ORAI1 RNA (siORAI1), 100 nM 1,25(OH)2D3, or 100 nM parathyroid hormone (PTH). Intracellular Ca2+ concentration was markedly lower in HYPOCAL. In addition, ORAI1 was detected in PMNL plasma membrane via FACS and was markedly lower in cows with HYPOCAL. Migration, adhesion capacity, and phagocytosis rate of PMNL were lower in response to HYPOCAL. Furthermore, plasma and PMNL concentration of nucleosome assembly protein (NAP2) and pro-platelet basic protein (CXCL7) was markedly lower with HYPOCAL. All these changes were associated with lower ROS production by PMNL. Thapsigargin and ionomycin treatment in vitro increased ORAI1 expression, migration of PMNL, adhering capacity, phagocytosis rate, and ROS production; conversely, those effects were abrogated by siORAI1 and ORAI1 inhibitor 2APB treatment. Also cytosolic Ca2+ concentration and ORAI1 abundance were increased by 1,25(OH)2D3 and PTH supplementation. Overall, the data indicate that failure of PMNL to uptake Ca2+ due to downregulation of ORAI1 during subclinical hypocalcemia is a factor contributing to impaired PMNL function. In addition, plasma PTH or 1,25(OH)2D3 could regulate ORAI1 and also participate in the regulation of PMNL activity.

Cow-level factors associated with subclinical hypocalcemia at calving in multiparous Jersey cows

The objective of our study was to identify cow-level factors associated with subclinical hypocalcemia at calving (SCH) in multiparous Jersey cows. A total of 598 Jersey and 218 Jersey × Holstein crossbreed cows from 2 commercial dairy herds were enrolled in a retrospective cohort study. Blood samples to determine total Ca concentration were collected from the coccygeal vessels at 3 h 19 min (±2 h 33 min) after calving. We used 2 serum Ca concentration thresholds to define SCH: <2.00 mmol/L (SCH-2.00) and <2.12 mmol/L (SCH-2.12). We evaluated the association of cow-level factors with SCH with multivariable Poisson regression models. Variables evaluated for association with SCH were herd; parity (2, 3, and ≥4); breed; previous lactation length and 305-d mature-equivalent milk yield; previous lactation first test milk yield and last test somatic cell count; lengths of calving interval, gestation, dry, and close-up periods; body condition and locomotion scores at calving; calving ease; and calf sex for singletons. We categorized continuous variables into quartiles (≤25th percentile, interquartile range and ≥75th percentile). The prevalence of SCH among Jersey cows was 40 (SCH-2.00) and 64% (SCH-2.12). Jersey cows of higher parity had greater risk of SCH-2.00 and SCH-2.12. The risk of SCH-2.12 was higher after birthing male calves. We also found a tendency for previous lactation length and previous lactation 305-d mature-equivalent milk yield effect to affect risk of SCH-2.12. The risk of SCH-2.12 was lower for cows that had a previous lactation length shorter than the 25th percentile compared with cows that had a previous lactation length within the interquartile range. The risk of SCH-2.12 was higher for cows that had a previous lactation 305-d mature-equivalent milk yield below the 25th percentile compared with cows that had a previous lactation 305-d mature-equivalent milk yield above the 75th percentile. Also, Jersey × Holstein crossbreed was associated with increased risk of SCH-2.00. In the multivariable analysis, we observed no association between SCH and previous lactation first test milk yield; last test somatic cell count; lengths of calving interval, gestation, dry, and close-up periods; body condition and locomotion scores at calving; and calving ease. Our study identified parity, breed, calf sex, previous lactation length, and previous lactation 305-d mature-equivalent milk yield as cow-level factors associated with SCH in multiparous Jersey cows.

Effects of feeding synthetic zeolite A during the prepartum period on serum mineral concentration, oxidant status, and performance of multiparous Holstein cows

The objective of this study was to determine the effects of feeding synthetic zeolite A for 3 wk before expected calving on peripartal serum mineral concentrations, hypocalcemia, oxidant status, and performance. Holstein cows (n = 55) entering their second or greater lactations were assigned randomly to 1 of 2 dietary treatments starting 21 d before expected calving: control (CON: 40% corn silage, 33% wheat straw, and 27% concentrate; n = 29) or experimental [EXP: CON plus zeolite A (X-Zelit, Protekta Inc., Lucknow, ON, Canada/Vilofoss, Graasten, Denmark; n = 26) at an inclusion rate of 3.3% of dry matter, targeting 500 g/d as-fed]. Cows were fed the same postpartum diet and housed in individual tiestalls through 28 d in milk. Cows fed EXP had higher serum Ca concentrations as parturition approached and during the immediate postpartum period. Serum P concentrations were lower for the EXP-fed cows during the prepartum period and the first 2 d of lactation, whereas serum Mg concentrations were lower than those of the CON-fed cows only during the immediate periparturient period. Cows fed EXP had decreased prevalence of subclinical hypocalcemia (SCH) from d -1 through 3 relative to day of parturition, with the largest difference occurring within the first day postpartum. Prepartum dry matter intake tended to be decreased and rumination was decreased in cows fed EXP; however; postpartum dry matter intake, rumination, milk yield, milk component yield, and colostrum measurements did not differ between treatments. Cows fed EXP tended to have increased hazard of pregnancy by 150 d in milk when controlling for parity compared with CON-fed cows; potential reproductive benefits merit further study. This study demonstrated that zeolite A supplementation during the prepartum period results in markedly improved serum Ca concentrations around parturition and similar postpartum performance compared with controls and is effective at decreasing hypocalcemia in multiparous Holstein cows.

The evaluation of superoxide dismutase activity, neutrophil function, and metabolic profile in cows with retained placenta

The present study aimed to determine the alterations in pre- and postpartum immune function, superoxide dismutase (SOD) activity, and serum metabolite changes in Brown Swiss cows with or without retained placenta (RP). Peripheral blood was sampled at −10 ± 4 days antepartum and 10 ± 4 days postpartum for the assessment of neutrophil phagocytic and oxidative burst activities by using flow cytometry. SOD activity, beta hydroxybutiric acid (BHB), nonesterified fatty acids (NEFA), calcium (Ca), phosphorus, aspartate aminotransferase (AST), alkaline phosphatase (ALP), alanine aminotransferase (ALT), creatinine kinase (CK), gamma-glutamyl transferase (GGT), lactate dehydrogenase, bilirubin, cholesterol, glucose, urea, albumin, total protein, and triglyceride concentrations were also measured from serum samples collected at −10 ± 4, 3 ± 1, 10 ± 4, and 30 ± 4 days relative to parturition. All data were analyzed using the MIXED procedure of SPSS. Neutrophil phagocytic and oxidative burst activities, phagocytic and oxidative fluorescence intensity, and phagocytic and oxidative indexes were similar among the groups (P > 0.05). However, serum SOD activity was 30 ± 4 IU/ml and 17 ± 2 IU/mL for cows that subsequently developed RP and healthy cows at −10 ± 4 days antepartum, respectively (P < 0.05). Body condition scores were similar in both groups (P > 0.05). All investigated serum metabolic parameters varied significantly over time (P < 0.001). Cows affected with RP had subclinical hypocalcemia (8.06 ± 0.3 mg/dl) and had significantly higher BHB levels (1027 ± 137.9 mmoL/l) at 3 ± 1 days postpartum. Furthermore, these cows had greater AST and NEFA concentrations around calving (P < 0.05). In conclusion, retained placenta had no prolonged effect on the measures of neutrophil function during the postpartum period. On the other hand, increased antepartum SOD activity might be a predisposing factor and can be used as a predictive biomarker for retained placenta.

Effects of dietary Zeolite supplementation on milk yield and composition and blood minerals status in lactating dairy cows

ABSTRACT The purpose of this study was to determine effects of inclusion of Zeolite in lactating dairy cows’ rations on blood Ca, P, and Mg status during periparturient period, as well as on milk yield and composition during early lactation. Forty-two pregnant dry Holstein cows were randomly assigned as Zeolite treated cows (EG) or untreated cows (CG) comprising 21 cows each. The EG group received the same diet as the CG group, but with addition of 200 g/cow/day of Zeolite. There was no treatment effect on milk total solids, milk fat, milk protein, lactose, milk ash, milk Ca, milk P, milk Mg, plasma P, and plasma Mg for CG and EG. Conversely, milk yield, fat corrected milk (FCM), fat yield, protein yield, lactose yield, and plasma Ca were significantly increased by Zeolite addition. These results indicate that Zeolite can be effectively used in the rations of dry and lactating cows with positive effects on milk production and components yields and no deleterious effects on milk composition or blood parameters. Blood Ca was enhanced around calving and at the beginning of lactation. It is suggested that prepartum Zeolite supplementation may alleviate the negative Ca balance and therefore reduce the incidence of subclinical hypocalcaemia during the periparturient period.

Risk factors for subclinical hypocalcaemia, and associations between subclinical hypocalcaemia and reproductive performance, in pasture-based dairy herds in New Zealand

AIMSTo estimate the herd-level prevalence of subclinical hypocalcaemia within 3 days of calving, to determine cow and herd-level risk factors for this condition, and associations with reproductive performance, in pasture-based cows in New Zealand.METHODSBetween 10 and 15 clinically healthy cows ≥3-years-old (n=1,051) were enrolled from 76 spring-calving dairy herds. Blood samples were collected from all cows on 1 or 2 days within 3 days of calving, and assayed for total concentrations of Ca in serum. Subclinical hypocalcaemia was defined as concentrations of Ca in serum ≤2.14 mmol/L, and herd-level prevalence was the percentage of sampled cows with subclinical hypocalcaemia. Breeding and pregnancy diagnosis data were obtained for each cow to calculate reproductive outcomes. Herd-level data about management practices were collected from farmers at enrolment. Associations between cow-level variables, and reproductive outcomes, and subclinical hypocalcaemia were examined using multivariable logistic regression mixed models. Associations between herd-level variables and prevalence of subclinical hypocalcaemia were examined using a multivariable linear regression model.RESULTSMean herd-level prevalence of subclinical hypocalcaemia was 52 (95% CI=49–55)%. Risk of subclinical hypocalcaemia at the cow-level was associated with an interaction between age of cow and interval from calving to sampling (p=0.03). Increasing age of cow was associated with increased risk of subclinical hypocalcaemia, and cows sampled on the day of calving had an increased risk compared with cows sampled 1 or 2 days after calving. Increased herd-level prevalence of subclinical hypocalcaemia was associated with feeding grass silage (p=0.06) or maize silage (p=0.004), and feeding increasing amounts of elemental Mg in the form of magnesium oxide (p=0.02). The mean farmer-reported herd-level prevalence of clinical hypocalcaemia was 2.9 (95% CI=2.1–3.8)%. Subclinical hypocalcaemia was not associated with any of the reproductive outcomes measured.CONCLUSIONS AND CLINICAL RELEVANCEThere was a high prevalence of subclinical hypocalcaemia in the pasture-fed, spring-calving dairy herds sampled and a large between-herd variation in prevalence. Subclinical hypocalcaemia increased with increasing age, and declined with time postpartum. Herd-level prevalence was associated with feeding grass silage and maize silage to pre-calving cows and with increasing amounts of supplemented magnesium oxide. Subclinical hypocalcaemia was not associated with reproductive outcomes.

Effect of treatment with oral Ca boluses following calving on concentrations of Ca in serum in pasture-based dairy cows

AIMSTo assess the effect of the administration of two oral Ca boluses on concentrations of total Ca, β-hydoxybutyrate (BHB) and non-esterified fatty acids (NEFA) in serum, and urine pH, in recently calved pasture-fed dairy cows.METHODSFriesian or Friesian cross Jersey cows from one dairy farm were blocked by age and randomly assigned to no treatment (control; n=14), or treatment (n=13) with two oral Ca boluses administered approximately 12 hours apart, with the first bolus being given within 14 hours of calving. Each bolus weighed 198 g and contained 43 g of Ca; 31 g of Ca from calcium chloride and 12 g of Ca from calcium sulfate. Cows were enrolled over three calendar days, and all cows were managed in one group during the 24-hour study period. Blood samples were collected at 0, 1, 2, 4, 8, 12, 13, 14, 16, 20 and 24 hours after the initial treatment. Serum from each time point was analysed for concentrations of total Ca, and from 0, 12, and 24 hours for NEFA and BHB. Urine was collected at 0, 12 and 24 hours for pH measurement and pH was categorised as <7 or ≥7. The effect of treatment on percentage change in concentrations of Ca in serum relative to 0 hours, and concentrations of NEFA, BHB and urine pH, was examined using multivariable repeated measures mixed models with cow as a random effect.RESULTSIn the final multivariable model for percentage change in concentrations of Ca, there was an interaction between time and treatment (p=0.004), with the percentage increase being higher in treatment than control cows at 1, 2, 4, 8 and 13 hours. At 12 hours, 5/13 (41%) treated cows had a urine pH <7compared to 0/12 (0%) control cows (p<0.001), and at 24 hours 13/13 (100%) treated cows had urine pH <7 compared to 0/12 (0%) control cows (p<0.001). Over the 24-hour period, mean concentrations of NEFA or BHB in serum were similar in treated and control cows (p>0.3).CONCLUSIONS AND CLINICAL RELEVANCEOral treatment with two Ca boluses increased concentrations of total Ca in serum and decreased urine pH in pasture-fed cows. This bolus has the potential to reduce the prevalence and duration of subclinical hypocalcaemia in recently calved cows.

Effects of postpartum oral calcium supplementation on productive and reproductive outcomes in multiparous Jersey cows

The detrimental effects that subclinical hypocalcemia has on postpartum performance, and the lack of a cow-side diagnostic tool, drives researchers to focus on designing preventive management strategies. The objectives of this study were to evaluate the effect of prophylactic supplementation with oral calcium boluses after calving on productive and reproductive outcomes.

Epidemiology of subclinical hypocalcemia in early-lactation Holstein cows

Hypocalcemia is one of the most common periparturient abnormalities afflicting dairy cows. The disorder is frequently divided into a clinical (i.e., parturient paresis) and a subclinical state, with the latter receiving much recent research attention. For classification purposes, subclinical hypocalcemia (SCH) should be defined as low blood Ca concentrations that are associated with periparturient health disorders, poorer production and reproduction outcomes, or both, without associated signs of postpartum paresis. Our objective was to characterize the epidemiology of SCH in Holstein cows by assessing the temporal associations of plasma Ca concentrations in the first 4 days-in-milk (DIM) with the risk of cows being diagnosed with metritis/and or displaced abomasum in the first 60 DIM and milk production across the first 15 wk of lactation.

Associations of subclinical hypocalcemia with fertility in a herd of grazing dairy cows

The main objective was to assess the associations of subclinical hypocalcemia (SCH), diagnosed at parturition (SCH-0) and 7 d in milk (SCH-7), with fertility in a herd of grazing dairy cows. Additional objectives were to characterize Ca concentration on 0 and 7 d in milk (DIM), assessing the risk factors for SCH-0 and SCH-7 and also the relationship with health status (metritis, endometritis, subclinical ketosis, and culling). A prospective observational study was carried out in a dairy farm in Argentina. Holstein cows (n = 126) were body condition scored (BCS, 1-5) on -21 ± 3, 0, 7 ± 3, and 28 ± 7 DIM and blood was collected on 0 and 7 ± 3 DIM to determine Ca and β-hydroxybutyrate concentrations. Calcium concentrations <2.0 and <2.14 mmol/L were used to define SCH-0 and SCH-7, respectively. The associations of SCH with (1) the odds for pregnancy to first service (P1AI) and pregnancy by 100 DIM (P100) were evaluated by logistic models, (2) the services per pregnancy was evaluated by a Poisson regression model, and (3) the hazards of insemination and pregnancy were evaluated with proportional hazards regression models whereas median days from calving to first insemination and to pregnancy were estimated by Kaplan-Meier method. Additionally, Ca concentration was assessed by linear regression models, and the associations of SCH-0 and SCH-7 with the odds for metritis, endometritis, subclinical ketosis, and culling were evaluated by logistic models. Calcium concentrations were similar at 0 and 7 DIM (2.40 vs. 2.41 mmol/L, respectively); they were higher in cows calving in fall than in summer (2.58 vs. 2.24 mmol/L), and they also were higher in primiparous than in multiparous cows (2.53 vs. 2.28 mmol/L, respectively). The proportion of cows having SCH-0 and SCH-7 was 27.3 and 39.3%, respectively. Fall-calving cows had lower odds for SCH-0 [odds ratio (OR) = 0.31, 95% confidence interval (CI) = 0.12-0.86] than summer-calving cows, multiparous cows had higher odds for SCH-0 (OR = 3.96, 95% CI = 1.09-14.39) than primiparous cows, and cows with prepartum BCS ≥3.00 had higher odds for SCH-0 (OR = 4.03, 95% CI = 1.17-13.89) than in cows with BCS <3.00. Conversely, parity and prepartum BCS were not important predictors for SCH-7. Surprisingly, SCH-0 was not a risk factor for SCH-7. Cows with SCH-0 had lower odds for P1AI (OR = 0.26, 95% CI = 0.07-0.99) than normocalcemic cows, given that P1AI was 14 versus 38%, respectively. The hazard of first service was not associated with SCH-0 (hazard ratio = 1.03, 95% CI = 0.63-1.70) but cows with SCH-0 had lower hazard of pregnancy (hazard ratio = 0.39, 95% CI = 0.16-0.98) and took 32 d longer to get pregnant (105 vs. 73) than normocalcemic cows. Conversely, SCH-7 was not associated with fertility. Finally, SCH-0 and SCH-7 were associated with the odds for subclinical ketosis and metritis, respectively. In conclusion, SCH-0 but not SCH-7 is associated with reduced fertility in a herd of grazing dairy cows, but both were associated with health status.

Hipocalcemia subclínica en ganado vacuno lechero: tratamiento y manejo preventivo. Revisión bibliográfica

Hypocalcemia is the most prevalent metabolic disease in high-yielding cows. Some authors place it around 65% (Martinez et al., 2012) and 78% (Rodriguez et al., 2017), in the period near parturition. The development of the subclinical disease can occur between 24 hours prior to parturition and 40 hours after it. It is due to a decrease in total serum calcium (below 8.5 mg/dl). Moreover, the homeostatic mechanisms available in the organism are not able to reestablish the plasmatic levels of this mineral. This metabolic disease has consequences on the production and on the health of the herd. The decrease of this metabolite results in a cascade of diseases which causes significant losses in the farm account. The diagnosis of this pathology takes place in the herd by measuring the total serum calcium in blood in dairy cows that are in period of transition. This has contributed to the fact that most of the issued studies are aimed at testing a nutritional model, molecule or pharmacological substance that contributes to decreasing the prevalence of subclinical hypocalcemia. The goal of this study has been to evaluate the results obtained in different papers published, in order to establish the best preventive strategy of subclinical hypocalcemia. It also aims at introducing the most recent investigations developed in this area

Prevalence of subclinical hypocalcemia in dairy cows in the Sousa city micro-region, Paraíba state.

Subclinical hypocalcemia is a metabolic disorder characterised by a decrease in serum calcium (Ca) levels, with no clinical symptoms. The aim of this study was to determine the punctual prevalence of subclinical hypocalcemia in dairy cows, in the Sousa city micro-region, Paraíba state. Samples were collected from 29 dairy farms, consisting of 153 and 296 blood samples in the pre- and postpartum period respectively. In relation to the mineral supplementation profile, 89.25% of the properties use a commercial supplement. On average, 40.53% of lactating cows presented total serum Ca levels under the lower limit of 8.0mg/dL, with an exclusive supplement of NaCl resulting in a higher percentage of cows, 61.11%, with the condition of subclinical hypocalcemia. For ionized Ca, the average prevalence of subclinical hypocalcemia was 21.16%. The prevalence of subclinical hypocalcemia for total serum Ca was 37.25 and 42.23% of cows in the pre- and postpartum period respectively. The type of mineral supplement did not influence (P > .05) total and ionized serum Ca levels in lactating cows. There was no significant difference (P > .05) for total and ionized serum Ca levels as a function of the reproductive period in lactating cows. Subclinical hypocalcemia was evident in the dairy cows under evaluation and occurred with an average punctual prevalence of 40.34%. Commercial supplement is the most common form of mineral mixture used; however, it was not able to promote an increase in the levels of total and ionized serum Ca levels due to errors in managing the supply.

Epidemiology of subclinical hypocalcemia in early-lactation Holstein dairy cows: The temporal associations of plasma calcium concentration in the first 4 days in milk with disease and milk production

The objectives of this study were to characterize the epidemiology of subclinical hypocalcemia (SCH) in Holstein dairy cows by assessing the temporal associations of plasma Ca concentrations in the first 4 d in milk (DIM) with the risk of cows being diagnosed with metritis or displaced abomasum (or both), and milk production across the first 15 wk of lactation. A prospective cohort study was conducted in 2 dairy herds in New York State, in which cows had a blood sample collected daily for the first 4 DIM. A total of 396 Holstein cows (137 primiparous and 259 multiparous) were enrolled. Multivariable Poisson regression models were built to evaluate the associations of plasma Ca concentration at each of the 4 d following parturition with the risk of primiparous cows being diagnosed with metritis and multiparous cows being diagnosed with metritis, displaced abomasum, or both. Similarly, generalized linear mixed models were built to evaluate the associations of plasma Ca concentration with milk production across the first 15 wk of lactation. Plasma Ca concentration was assessed on a continuous scale in all models; dichotomization and SCH classification only occurred in the final models if the Ca concentration variable was meaningful by creating an optimized threshold based on receiver operating characteristic curve analysis. Plasma Ca concentration assessed at 1 DIM was not associated with the risk of metritis in primiparous cows, but an association was observed at 2, 3, and 4 DIM (critical thresholds were plasma Ca concentration ≤2.15, 2.10, and 2.15 mmol/L, respectively). Plasma Ca concentration was associated with the risk of metritis or displaced abomasum diagnosis (or both) for 2nd parity animals at 2 DIM (threshold ≤1.97 mmol/L), and at 4 DIM for 3rd and greater lactations (threshold ≤2.20 mmol/L). Reduced plasma Ca concentration was associated with higher milk production when assessed at 1 DIM in primiparous and multiparous cows, and lower milk production when assessed at 4 DIM in multiparous cows only. For primiparous cows, plasma Ca concentration was not associated with lower milk production at any of the DIM assessed. In conclusion, assessments of SCH at the individual cow level must take into account the DIM of Ca concentration measurement and parity of the cow, as the epidemiology of the disorder was demonstrated to be highly dependent on these variables. This study advances the knowledge of the epidemiology of SCH and better establishes thresholds for optimizing SCH diagnosis.

Can neutral dietary cation-anion difference (DCAD) decrease occurrence of clinical periparturient hypocalcaemia in dairy cattle?

Adjusting the dietary cation-anion difference (DCAD) is one of the most efficient ways to stimulate calcium homeostasis in periparturient dairy cattle. However, adjusting DCAD to the recommended negative values (-100 to -150 mEq/kg) is associated with decreased food intake and metabolic acidosis. The critical conditions of the animals at peripartum (i.e. drastic hormonal changes, decreased appetite and negative energy balance) can be detrimental to the health, productivity and welfare of the animals if combined with decreased feed intake caused by unpalatable acidogenic salts. In a cross-sectional study, we analysed the ration of eight small to large dairy herds with intensive husbandry systems, including 6949 dry cows. Sodium, potassium, chlorine and sulfur concentrations in the feed were determined and DCAD was calculated. The DCAD of the ration of the farms ranged from -33.5 to +24.7 mEq/kg. Parturient paresis (PP, or milk fever) prevalence was investigated and correlated to DCAD values. Clinical PP occurrence in the dairies of this investigation on average declined by 87% (ranging from a 97% decline to 5% increase). This indicates that adjusting DCAD at neutral values (0 ± 30 mEq/kg range) may both lower the PP prevalence and increase ration palatability by lowering acidogenic salts in the ration. Further research is recommended to investigate the effects of neutral DCAD on subclinical hypocalcaemia and food intake of the cattle.

Effects of some diseases observed at postpartum period of cows in dairy farms: Economic perspective

In this study, financial losses due to several endemic diseases at the postpartum period of dairy cows were calculated, using the incidence rates and the financial losses from each clinical case of the endemic diseases reported in the literature. The median values of the incidence rates reported in the literature for retained placenta, clinical hypocalcemia, subclinical hypocalcemia, clinical metritis, clinical mastitis, clinical ketosis, subclinical ketosis, lameness and displaced abomasum were 8.6, 3.9, 33, 13.3, 7, 2.5, 19.8, 4.3 and 1.8% respectively. The average losses per case arising from retained placenta, clinical hypocalcemia, clinical metritis, clinical mastitis, clinical ketosis, lameness and displaced abomasum were calculated to be $257, $279, $278, $212, $109, $223 and $340 respectively. Using the above stated findings, the financial losses for each average cow arising from retainedplacenta, clinical hypocalcemia, clinical metritis, clinical mastitis, clinical ketosis, lameness, displaced abomasum and the total of 7 diseases were estimated to be $22, $11, $37, $15, $3, $9, $6 and $103 respectively.