Effect of dietary cation-anion difference on acid-base status and dry matter intake in dry pregnant cows

The objective was to determine if the reduction in dry matter (DM) intake of acidogenic diets is mediated by inclusion of acidogenic products, content of salts containing Cl, or changes in acid-base status. The hypothesis was that a decrease in intake is mediated by metabolic acidosis. Ten primigravid Holstein cows at 148 ± 8 d of gestation were used in a duplicated 5 × 5 Latin square design. The dietary cation-anion difference (DCAD) of diets and acid-base status of cows were manipulated by incorporating an acidogenic product or by adding salts containing Cl, Na, and K to the diets. Treatments were a base diet (T1; 1.42% K, 0.04% Na, 0.26% Cl; DCAD = 196 mEq/kg); the base diet with added 1% NaCl and 1% KCl (T2; 1.83% K, 0.42% Na, 1.23% Cl; DCAD = 194 mEq/kg); the base diet with added 7.5% acidogenic product, 1.5% NaHCO₃, and 1% K₂CO₃ (T3; 1.71% K, 0.54% Na, 0.89% Cl; DCAD = 192 mEq/kg); the base diet with added 7.5% acidogenic product (T4; 1.29% K, 0.13% Na, 0.91% Cl; DCAD = ?114 mEq/kg); and the base diet with 7.5% acidogenic product, 1% NaCl, and 1% KCl (T5; 1.78% K, 0.53% Na, 2.03% Cl; DCAD = ?113 mEq/kg). Periods lasted 14 d with the last 7 d used for data collection. Feeding behavior was evaluated for 12 h in the last 2 d of each period. Reducing the DCAD by feeding an acidogenic product reduced blood pH (T1 = 7.450 vs. T2 = 7.436 vs. T3 = 7.435 vs. T4 = 7.420 vs. T5 = 7.416) and induced a compensated metabolic acidosis with a reduction in bicarbonate, base excess, and partial pressure of CO₂ in blood, and reduced pH and strong ion difference in urine. Reducing the DCAD reduced DM intake 0.6 kg/d (T1 = 10.3 vs. T4 = 9.7 kg/d), which was caused by the change in acid-base status (T2 + T3 = 10.2 vs. T4 + T5 = 9.6 kg/d) because counteracting the acidifying action of the acidogenic product by adding salts with strong cations to the diet prevented the decline in intake. The decline in intake caused by metabolic acidosis also was observed when adjusted for body weight (T2 + T3 = 1.75 vs. T4 + T5 = 1.66% BW). Altering the acid-base status with acidogenic diets reduced eating (T2 + T3 = 6.7 vs. T4 + T5 = 5.9 bouts/12 h) and chewing (T2 + T3 = 14.6 vs. T4 + T5 = 13.5 bouts/12 h) bouts, and extended meal duration (T2 + T3 = 19.8 vs. T4 + T5 = 22.0 min/meal) and intermeal interval (T2 + T3 = 92.0 vs. T4 + T5 = 107.7 min). Results indicate that reducing the DCAD induced a compensated metabolic acidosis and reduced DM intake, but correcting the metabolic acidosis prevented the decline in DM intake in dry cows. The decrease in DM intake in diets with negative DCAD was mediated by metabolic acidosis and not by addition of acidogenic product or salts containing Cl.     

Effects of prepartum dietary cation-anion difference and source of vitamin D in dairy cows: Vitamin D,mineral, and bone metabolism

Pregnant Holstein cows, 28 nulliparous and 51 parous, were blocked by parity and milk yield and randomly allocated to receive diets that differed in dietary cation-anion difference (DCAD), +130 or ?130 mEq/kg, and supplemented with either calcidiol or cholecalciferol at 3 mg/11 kg of dry matter from 255 d of gestation until parturition. Blood was sampled thrice weekly prepartum, and on d 0, 1, 2, 3, 6, 9, 12, 15, 18, 21, 24, 27, and 30 postpartum to evaluate effects of the diets on vitamin D, mineral and bone metabolism, and acid-base status. Blood pH and concentrations of minerals, vitamin D metabolites, and bone-related hormones were determined, as were mineral concentrations and losses in urine and colostrum. Supplementing with calcidiol increased plasma concentrations of 25-hydroxyvitamin D₃, 3-epi 25-hydroxyvitamin D₃, 25-hydroxyvitamin D₂, 1,25-dihydroxyvitamin D₃, and 24,25-dihydroxyvitamin D₃ compared with supplementing with cholecalciferol. Cows fed the diet with negative DCAD had lesser concentrations of vitamin D metabolites before and after calving than cows fed the diet with positive DCAD, except for 25-hydroxyvitamin D₂. Feeding the diet with negative DCAD induced a compensated metabolic acidosis that attenuated the decline in blood ionized Ca (iCa) and serum total Ca (tCa) around calving, particularly in parous cows, whereas cows fed the diet with positive DCAD and supplemented with calcidiol had the greatest 1,25-dihydroxyvitamin D₃ concentrations and the lowest iCa and tCa concentrations on d 1 and 2 postpartum. The acidogenic diet or calcidiol markedly increased urinary losses of tCa and tMg, and feeding calcidiol tended to increase colostrum yield and increased losses of tCa and tMg in colostrum. Cows fed the diet with negative DCAD had increased concentrations of serotonin and C-terminal telopeptide of type 1 collagen prepartum compared with cows fed the diet with positive DCAD. Concentrations of undercarboxylated and carboxylated osteocalcin and those of adiponectin did not differ with treatment. These results provide evidence that dietary manipulations can induce metabolic adaptations that improve mineral homeostasis with the onset of lactation that might explain some of the improvements observed in health and production when cows are fed diets with negative DCAD or supplemented with calcidiol.     

Metabolic and blood acid-base responses to prepartum dietary cation-anion difference and calcium content in transition dairy cows

Dairy cows commonly undergo negative Ca balance accompanied by hypocalcemia after parturition. A negative dietary cation-anion difference (DCAD) strategy has been used prepartum to improve periparturient Ca homeostasis. Our objective was to determine the influence of a negative DCAD diet with different amounts of dietary Ca on the blood acid-base balance, blood gases, and metabolic adaptation to lactation. Multiparous Holstein cows (n = 81) were blocked into 1 of 3 dietary treatments from 252 d of gestation until parturition: (1) positive DCAD diet and low Ca (CON; containing +6.0 mEq/100 g DM, 0.4% DM Ca); (2) negative DCAD diet and low Ca (ND; ?24.0 mEq/100 g DM, 0.4% DM Ca); or (3) negative DCAD diet plus high Ca supplementation (NDCA; ?24.1 mEq/100 g DM, 2.0% DM Ca). There were 28, 27, and 26 cows for CON, ND, and NDCA, respectively. Whole blood was sampled at 0, 24, 48, and 96 h after calving for immediate determination of blood acid-base status and blood gases. Serum samples collected at ?21, ?14, ?7, ?4, ?2, ?1, at calving, 1, 2, 4, 7, 14, 21, and 28 d relative to parturition were analyzed for metabolic components. Results indicated that cows fed ND or NDCA had lower blood pH at calving but greater pH at 24 h after calving compared with CON. Blood bicarbonate, base excess, and total CO₂ (tCO₂) concentrations of cows in ND and NDCA groups were less than those of cows in CON at calving but became greater from 24 to 96 h postpartum. The NDCA cows had lower blood bicarbonate, base excess, and tCO₂ at 48 h and greater partial pressure of oxygen after calving compared with ND. Cows fed ND or NDCA diets had lower serum glucose concentrations than CON cows before calving but no differences were observed postpartum. Serum concentrations of total protein and albumin were greater prepartum for cows in ND and NDCA groups than for those in CON. Postpartum serum urea N and albumin concentrations tended to be higher for ND and NDCA cows. Cows fed ND or NDCA diets had elevated serum total cholesterol concentration prepartum. During the postpartum period, triglycerides and NEFA of cows fed ND or NDCA diets tended to be lower than those of CON. Cows fed the NDCA diet had greater postpartum total cholesterol in serum and lower NEFA concentration at calving than ND. In conclusion, feeding a prepartum negative DCAD diet altered blood acid-base balance and induced metabolic acidosis at calving, and improved protein and lipid metabolism. Supplementation of high Ca in the negative DCAD diet prepartum was more favorable to metabolic adaptation to lactation in dairy cows than the negative DCAD diet with low Ca.     

Effects of level of dietary cation-anion difference and duration of prepartum feeding on performance and metabolism of dairy cows

The objectives were to evaluate the effects of feeding diets with 2 levels of negative dietary cation-anion differences (DCAD) during the last 42 or 21 d of gestation on performance and metabolism in dairy cows. The hypothesis was that extending feeding from 21 to 42 d and reducing the DCAD from ?70 to ?180 mEq/kg of dry matter (DM) would not be detrimental to performance. Holstein cows at 230 d of gestation were blocked by parity prepartum (48 entering their second lactation and 66 entering their third or greater lactation) and 305-d milk yield, and randomly assigned to 1 of 4 treatments arranged as a 2 × 2 factorial. The 2 levels of DCAD, ?70 or ?180 mEq/kg of DM, and 2 feeding durations, the last 21 d (short) or the last 42 d (long) prepartum resulted in 4 treatments, short ?70 (n = 29), short ?180 (n = 29), long ?70 (n = 28) and long ?180 (n = 28). Cows in the short treatments were fed a diet with DCAD of +110 mEq/kg of DM from ?42 to ?22 d relative to calving. After calving, cows were fed the same diet and production and disease incidence were evaluated for 42 d in milk, whereas reproduction and survival was evaluated for 305 d in milk. Blood was sampled pre- and postpartum for quantification of metabolites and minerals. Reducing the DCAD linearly decreased prepartum DM intake between ?42 and ?22 d relative to calving (+110 mEq/kg of DM = 11.5 vs. ?70 mEq/kg of DM = 10.7 vs. ?180 mEq/kg of DM = 10.2 ± 0.4), and a more acidogenic diet in the last 21 d of the dry period reduced intake by 1.1 kg/d (?70 mEq/kg of DM = 10.8 vs. ?180 mEq/kg of DM = 9.7 ± 0.5 kg/d). Cows fed the ?180 mEq/kg of DM diet had increased concentrations of ionized Ca in blood on the day of calving (?70 mEq/kg of DM = 1.063 vs. ?180 mEq/kg of DM = 1.128 ± 0.020 mM). Extending the duration of feeding the diets with negative DCAD from 21 to 42 d reduced gestation length by 2 d (short = 277.2 vs. long = 275.3 d), milk yield by 2.5 kg/d (short = 40.4 vs. long = 37.9 ± 1.0 kg/d) and tended to increase days open because of reduced pregnancy per artificial insemination (short = 35.0 vs. long = 22.6%). Results suggest that increasing the duration of feeding diets with negative DCAD from 21 to 42 d prepartum might influence milk yield and reproduction of cows in the subsequent lactation, although yields of 3.5% fat- and energy-corrected milk did not differ with treatments. Reducing the DCAD from ?70 to ?180 mEq/kg of DM induced a more severe metabolic acidosis, increased ionized Ca concentrations prepartum and on the day of calving, and decreased colostrum yield in the first milking, but had no effects on performance in the subsequent lactation. Collectively, these data suggest that extending the feeding of an acidogenic diet beyond 21 d is unnecessary and might be detrimental to dairy cows, and a reduction in the DCAD from ?70 to ?180 mEq/kg of DM is not needed.     

Prepartum level of dietary cation-anion difference fed to nulliparous cows: Acid-base balance,mineral metabolism,and health responses

Objectives were to determine the effects of 3 different levels of dietary cation-anion difference (DCAD) fed during the last 22 d of gestation to pregnant nulliparous cows on pre- and postpartum acid-base balance, mineral metabolism, and health responses. In all, 132 pregnant nulliparous Holstein cows were enrolled at 250 (248–253) d of gestation, blocked by genomic merit of energy-corrected milk yield, and assigned randomly to diets varying in DCAD: +200 (P200, n = 43), −50 (N50, n = 45), or −150 (N150, n = 44) mEq/kg of dry matter. Dietary treatments were fed until calving, after which cows received the same lactation diet for the first 100 d postpartum. Urine and blood were sampled throughout the prepartum period and in the first weeks postpartum, and urine was assessed for pH, whereas blood was analyzed for gases, measures of acid-base balance, minerals, and metabolites. Calcium (Ca) and magnesium (Mg) retention and phosphorus (P) digestibility were evaluated in the last week of gestation and first week of lactation. Incidence of diseases was evaluated for the first 100 d postpartum. Data are presented in sequence as P200, N50, N150 (LSM ± SEM). Reducing the DCAD reduced urine (8.17 vs. 6.50 vs. 5.51 ± 0.11) and blood pH (7.442 vs. 7.431 vs. 7.410 ± 0.004) and induced a state of compensated metabolic acidosis with a reduction in blood HCO₃⁻ (28.4 vs. 26.7 vs. 24.9 ± 0.3 mM) and partial pressure of CO₂ (41.8 vs. 40.1 vs. 39.1 ± 0.4 mmHg) prepartum. Reducing the DCAD linearly increased blood ionized Ca (iCa; 1.224 vs. 1.243 vs. 1.259 ± 0.008 mM) and serum total Ca (tCa; 2.50 vs. 2.53 vs. 2.56 ± 0.02 mM) prepartum, blood iCa on the day of calving, and serum Mg in the first days postpartum. Reducing the DCAD linearly increased the apparent absorption of Ca (12.9 vs. 19.0 vs. 20.9 ± 1.4 g/d) and Mg (7.0 vs. 9.9 vs. 10.4 ± 1.4 g/d) prepartum, but apparent retention of both Ca (13.9 g/d) and Mg (3.4 g/d) did not differ with treatment. Treatment did not affect digestibility of P pre- or postpartum or retention of Ca or Mg postpartum. Treatment did not affect the incidence or prevalence of subclinical hypocalcemia, hepatic composition, or the prevalence of fatty liver. Reducing the DCAD had a quadratic effect on incidence of fever (46.5 vs. 17.6 vs. 33.9 ± 7.0%), uterine diseases (36.3 vs. 25.6 vs. 46.0 ± 7.3%), and morbidity (41.4 vs. 28.1 vs. 55.6 ± 7.3%). Feeding a diet with −50 mEq/kg of dry matter promoted moderate changes in acid-base balance, altered mineral metabolism, and benefited health of nulliparous cows; however, further reducing the DCAD to −150 mEq/kg negated the benefits to health.     

Effects of prepartum dietary cation-anion difference and source of vitamin D in dairy cows: Lactation performance and energy metabolism

The objectives of this experiment were to evaluate the effects of feeding diets with 2 dietary cation-anion difference (DCAD) levels and supplemented with either cholecalciferol (CH) or calcidiol (CA) during late gestation on lactation performance and energetic metabolism in dairy cows. The hypothesis was that combining a prepartum acidogenic diet with calcidiol supplementation would benefit peripartum Ca metabolism and, thus, improve energy metabolism and lactation performance compared with cows fed an alkalogenic diet or cholecalciferol. Holstein cows at 252 d of gestation were blocked by parity (28 nulliparous and 51 parous cows) and milk yield within parous cows, and randomly assigned to 1 of 4 treatments arranged as a 2 × 2 factorial, with 2 levels of DCAD (positive, +130, and negative, ?130 mEq/kg) and 2 sources of vitamin D, CH or CA, fed at 3 mg per 11 kg of diet dry matter (DM). The resulting treatment combinations were positive DCAD with CH (PCH), positive DCAD with CA (PCA), negative DCAD with CH (NCH), or negative DCAD with CA (NCA), which were fed for the last 21 d of gestation. After calving, cows were fed the same lactation diet. Body weight and body condition were evaluated prepartum and for the first 49 d postpartum. Blood was sampled thrice weekly prepartum, and on d 0, 1, 2, 3, and every 3 d thereafter until 30 d postpartum for quantification of hormones and metabolites. Lactation performance was evaluated for the first 49 d postpartum. Feeding a diet with negative DCAD reduced DM intake in parous cows by 2.1 kg/d, but no effect was observed in nulliparous cows. The negative DCAD reduced concentrations of glucose (positive = 4.05 vs. negative = 3.95 mM), insulin (positive = 0.57 vs. negative = 0.45 ng/mL), and insulin-like growth factor-1 (positive = 110 vs. negative = 95 ng/mL) prepartum. Treatments did not affect DM intake postpartum, but CA-supplemented cows tended to produce more colostrum (PCH = 5.86, PCA = 7.68 NCH = 6.21, NCA = 7.96 ± 1.06 kg) and produced more fat-corrected milk (PCH = 37.0, PCA = 40.1 NCH = 37.5, NCA = 41.9 ± 1.8 kg) and milk components compared with CH-supplemented cows. Feeding the negative DCAD numerically increased yield of fat-corrected milk by 1.0 kg/d in both nulliparous and 1.4 kg/d in parous cows. Minor differences were observed in postpartum concentrations of hormones and metabolites linked to energy metabolism among treatments. Results from this experiment indicate that replacing CH with CA supplemented at 3 mg/d during the prepartum period improved postpartum lactation performance in dairy cows.     

Prepartum level of dietary cation-anion difference fed to nulliparous cows: Lactation and reproductive responses

Objectives were to determine the effects of 3 levels of dietary cation-anion difference (DCAD) fed prepartum to nulliparous cows on productive and reproductive performance. We enrolled 132 pregnant nulliparous Holstein cows at 250 (248–253) d of gestation in a randomized block design. Cows were blocked by genomic merit of energy-corrected milk yield and assigned randomly to diets varying in DCAD, +200 (P200; n = 43), −50 (N50; n = 45), or −150 (N150; n = 44) mEq/kg of dry matter (DM). Dietary treatments were fed during the last 22 d of gestation and, after calving, postpartum cows received the same lactation diet. Productive performance was evaluated for the first 14 wk of lactation, and reproduction was assessed until 305 d postpartum. Intake of DM prepartum decreased linearly (results presented in sequence as least squares means ± standard error of the mean, P200 vs. N50 vs. N150) with a reduction in DCAD (9.0 vs. 8.9 vs. 8.4 ± 0.1 kg/d), which resulted in linear decreases in net energy balance (0.34 vs. 0.20 vs. −0.36 ± 0.20 Mcal/d), body weight change (1.1 vs. 0.8 vs. 0.3 ± 0.1 kg/d), and mean body weight (652 vs. 649 vs. 643 ± 2 kg) prepartum. Treatment did not affect yield of colostrum (6.3 vs. 5.8 vs. 5.1 ± 0.6 kg) or the contents or yields of fat, protein, lactose, IgG, Ca, or Mg in colostrum. Intake of DM (19.4 vs. 19.2 vs. 19.0 ± 0.2 kg/d), yields of milk (36.6 vs. 36.7 vs. 35.8 ± 0.6 kg/d) or energy-corrected milk (36.7 vs. 36.3 vs. 35.9 ± 0.5 kg/d), feed efficiency (1.93 vs. 1.92 vs. 1.93 ± 0.03 kg of energy-corrected milk per kilogram of DM intake), and content and yield of milk components did not differ among treatments during the first 14 wk of lactation. Prepartum DCAD did not affect the cumulative milk yield by 305 d of lactation (9,653 vs. 10,005 vs. 9,918 ± 196 kg). Of the 132 cows, 40 P200, 45 N50, and 43 N150 received at least 1 artificial insemination (AI), and treatment did not affect pregnancy per AI at first (32.5 vs. 35.6 vs. 37.2%) or all AI (30.6 vs. 33.9 vs. 40.2%), although reducing the DCAD increased the proportion of cows pregnant by 305 d postpartum (76.7 vs. 88.9 vs. 93.2%) without altering the rate of pregnancy. Collectively, manipulating the DCAD of prepartum diets, from +200 to −150 mEq/kg of DM, fed to late gestation nulliparous cows did not affect subsequent lactation productive performance, but may have provided some benefit to reproduction, which warrants further confirmation.     

Timothy hays differing in dietary cation-anion difference affect the capability of dairy cows to maintain their calcium homeostasis

Forages low in dietary cation-anion difference (DCAD) can be used to decrease the DCAD in prepartum diet but the extent to which DCAD needs to be reduced is of recent interest. The objective of this study was to evaluate the effectiveness of timothy hays differing in DCAD at maintaining Ca homeostasis. Six nonlactating and nonpregnant multiparous Holstein cows were fed diets containing timothy (Phleum pratense L.) hay with DCAD values of 4.1 ± 3.6 (LOW), 14.1 ± 3.0 (MED), or 25.1 ± 2.5 (HIGH) mEq per 100 g of DM in a duplicated 3 × 3 Latin square design with 14-d experimental periods. The LOW and MED hays were produced by fertilizing established timothy fields at a rate of 224 kg CaCl₂ per ha, and HIGH hay was obtained from the same field where LOW hay was produced, but from a section not fertilized with CaCl₂. Experimental diets, containing LOW, MED, or HIGH timothy hay at 71% of dietary DM, had DCAD values of 0.7, 7.3, and 14.4 mEq per 100 g of DM, respectively. Animals were fed at 6% of metabolic body weight, which provided 108% of their daily energy requirement. For each period, after a 12 d diet adaptation, cows were subjected to an EDTA challenge (3 cows each on d 13 and 14). Infusion of EDTA solution into the jugular vein decreases the concentration of blood ionized Ca, and the EDTA challenge protocol determined the resistance time and recovery time: the time required for the blood ionized Ca concentration to decrease to 60%, and the time required to recover to 90% of the prechallenge concentrations, respectively. Urine pH was lower when cows were fed LOW compared with HIGH diet (6.88 vs. 7.83), but urine pH when cows were fed MED diet (7.15) did not differ from that when cows received the LOW or HIGH diet. However, immediately before the EDTA challenge, blood pH was lower when cows were fed LOW or MED compared with HIGH diet (7.44 vs. 7.47). Although the resistance time was not affected by treatments, the recovery time was shorter when cows were fed the LOW compared with MED or HIGH diet (185 vs. 248 and 263 min, respectively). Blood pH decreased when cows were fed the LOW or MED diet, but the capability to maintain Ca homeostasis was enhanced only when cows received the LOW diet, in which the DCAD value was decreased to 1 mEq per 100 g of DM.     

Comparison of 0.46% calcium diets with and without added anions with a 0.7% calcium anionic diet as a means to reduce periparturient hypocalcemia

Most studies demonstrating that diets with low dietary cation-anion difference (DCAD) reduce hypocalcemia in cows add enough anions to the diet to reduce urine pH below 7.0. One objective of these experiments was to determine whether there is any benefit to periparturient plasma Ca concentration if diet anion addition results in a lesser degree of acidification of the cow and urine pH does not go below 7.0. Another method for reducing hypocalcemia involves feeding a prepartal diet that is Ca deficient. This places the cow in negative Ca balance before calving, stimulating parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D secretion before calving and thus promoting Ca homeostasis at calving. As practiced in the field, low-Ca diets are often about 0.5% Ca. Our second objective was to determine whether a 0.46% Ca diet would be sufficiently low in Ca to stimulate PTH secretion before calving. A meta-analysis of the literature suggests that a 0.5% Ca, low-DCAD diet will reduce hypocalcemia better than a 0.7% Ca diet. A third objective was to compare periparturient plasma Ca in cows fed 0.46 or 0.72% Ca diets with similar DCAD. In experiment 1, anions (primarily chloride) or anions plus Ca were added to a 1.4% K basal diet to create the following diets: 0.46% Ca and +167 mEq/kg of DCAD, 0.46% Ca and ?13 mEq/kg of DCAD, and 0.72% Ca and ?17 mEq/kg of DCAD. In experiment 2, the same amounts of anion were added to a 2.05% K basal diet to create the following diets: 0.46% Ca and +327 mEq/kg of DCAD, 0.46% Ca and +146 mEq/kg of DCAD, and 0.72% Ca and +140 mEq/kg of DCAD. In experiment 1, cows fed the diet with 0.46% Ca and +167 mEq/kg of DCAD had significantly lower plasma Ca concentration after calving than cows fed the 0.46 or 0.72% Ca diets with anions. Periparturient plasma Ca concentrations did not differ in cows fed the low-DCAD diets with 0.46 or 0.72% Ca. Urine pH was reduced from 8.27 in the diet with 0.46% Ca and +167 mEq/kg of DCAD to 7.07 and 7.41 in the 0.46 and 0.72% Ca anion diets, respectively. Precalving plasma PTH and 1,25-dihydroxyvitamin D concentrations were similar in cows fed the 0.46% Ca diets and the 0.72% Ca diets, suggesting that the 0.46% Ca diets were not low enough in Ca to place the cow in negative Ca balance before calving. In experiment 2, adding the anion supplements to a 2.05% K diet did not reduce urine pH below 8.0. Periparturient plasma Ca concentrations did not differ in cows in any group in experiment 2. Precalving diets that are 0.46% Ca fed ad libitum are too high in Ca to stimulate Ca homeostasis before calving. Adding anions to a diet can benefit periparturient cow plasma Ca concentration, but only if it alters acid–base status enough to reduce urine pH below 7.5.     

Effect of prepartum anionic supplementation on periparturient feed intake, health, and milk production

Our objectives were to determine if dietary cation-anion difference (DCAD) and source of anions influence periparturient feed intake and milk production of dairy cattle during the transition period. Diets differed in DCAD (cationic or anionic) and anionic supplement. The 4 diets used prepartum were (1) control [DCAD +20 mEq/100 g of dry matter (DM)], (2) Bio-Chlor (DCAD −12 mEq/100 g of DM; Church & Dwight Co. Inc., Princeton, NJ), (3) Fermenten (DCAD −10 mEq/100 g of DM; Church & Dwight Co. Inc.), and (4) salts (DCAD −10 mEq/100 g of DM). Urine pH was lower for cows that consumed an anionic diet prepartum compared with control. Prepartum diet had no effect on prepartum dry matter intake (DMI) of multiparous or primiparous cows. Postpartum DMI and milk yield for multiparous cows fed anionic diets prepartum were greater compared with those fed the control diet. Postpartum DMI and milk yield of primiparous cows were similar for prepartum diets. Feeding prepartum anionic diets did not affect plasma Ca at or near calving. However, cows fed anionic diets began their decline in plasma Ca later than control cows. Postpartum β-hydroxybutyrate and nonesterified fatty acids were lower for primiparous cows fed prepartum anionic diets compared with those fed the control diet. Prepartum and postpartum plasma glucose concentrations were not affected by prepartum diet for all cows. Liver triglyceride differed for parity by day. Parities were similar at 21 d prepartum, but at 0 d and 21 d postpartum, levels were greater for multiparous cows. Results indicate that decreasing the DCAD of the diet during the prepartum period can increase postpartum DMI and milk production of multiparous cows without negatively affecting performance of primiparous cows.     

Effects of maternal level of dietary cation-anion difference fed to prepartum nulliparous cows on offspring acid-base balance,metabolism, and growth

The objectives were to determine the effects of dietary cation-anion difference (DCAD) fed to pregnant cows during the last 22 d of gestation on offspring acid-base balance, metabolism, growth, and health preweaning. A total of 132 nulliparous Holstein cows were enrolled at 250 (248 to 253) d of gestation in a randomized block design. Cows were blocked by genomic merit of energy-corrected milk yield and assigned randomly to diets varying in DCAD: +200 (P200, n = 43), ?50 (N50, n = 45), or ?150 (N150, n = 44) mEq/kg of dry matter (DM). Newborn calves (15 males and 28 females in P200, 22 males and 23 females in N50, and 18 males and 26 females in N150) were followed for the first 7 or 56 d of age if males or females, respectively. Measures of acid-base balance and concentrations of minerals in blood were measured in all calves on d 0 before colostrum feeding, and on d 1, 3, and 7. Each calf was fed 3.78 L of colostrum from the respective treatment, and apparent efficiency of IgG absorption was determined. All calves were weighed at birth, and females were weighed again at 21, 42, and 56 d of age. Concentrations in serum of total calcium (tCa), total magnesium (tMg), and total phosphorus (tP) were measured up to 56 d of age; intakes of milk and starter grain DM were measured daily from 21 to 56 d of age; and incidence of disease was recorded for the first 56 d of age in females. Treatment did not affect acid-base balance measured in all calves. Calves were born with metabolic and respiratory acidosis, which reversed by 1 d of age. In the first 24 h after birth, blood pH increased from 7.215 to 7.421 and bicarbonate from 26.2 to 31.7 mM, whereas partial pressure of CO₂ decreased from 64.1 to 48.7 mm of Hg in all treatments. Maternal DCAD did not affect colostrum IgG content fed to calves (P200 = 95.0 vs. N50 = 91.0 vs. N150 = 97.1 ± 4.1 g/L) or apparent efficiency of IgG absorption (P200 = 33.1 vs. N50 = 33.1 vs. N150 = 34.2 ± 1.9%). Males were born heavier than females, but maternal DCAD did not affect birth weight of all calves (P200 = 37.7 vs. N50 = 37.3 vs. N150 = 37.8 ± 0.7 kg) or daily weight gain in females in the first 56 d of life (P200 = 0.80 vs. N50 = 0.81 vs. N150 = 0.77 ± 0.03 kg/d). Treatment did not affect intake of milk (P200 = 1.11 vs. N50 = 1.04 vs. N150 = 1.19 ± 0.06 kg/d) or starter grain DM (P200 = 0.27 vs. N50 = 0.27 vs. N150 = 0.21 ± 0.06 kg/d), or measures of feed efficiency. Treatment did not affect concentrations of minerals in serum, morbidity, or age at morbidity. Manipulating the DCAD of pregnant nulliparous dams during late gestation did not affect offspring performance in the first 2 mo of age.     

Interaction of 5-hydroxy-l-tryptophan and negative dietary cation-anion difference on calcium homeostasis in multiparous peripartum dairy cows

Hypocalcemia affects almost 50% of all dairy cows. Our laboratory has previously demonstrated that infusions of the serotonin precursor 5-hydroxy-l-tryptophan (5-HTP) increase circulating calcium concentrations in the Holstein transition cow. It is unknown whether feeding a negative dietary cation-anion difference (DCAD) diet alters the relationship between 5-HTP and hypocalcemia. The main objective of this study was to determine whether feeding a negative DCAD (?DCAD) diet before calving in conjunction with 5-HTP treatment could further diminish the magnitude of hypocalcemia at the time of calving. We used a randomized complete block design with a 2 × 2 factorial arrangement. Thirty-one multiparous Holstein cows were fed either a positive (+13 mEq/100 g) or negative (?13 mEq/100 g) DCAD diet 21 d before parturition and were intravenously infused daily with saline or 5-HTP (1 mg/kg) starting 7 d before the estimated date of parturition. Cows were blocked by parity and were randomly assigned to 1 of 4 treatment groups: positive DCAD plus saline, positive DCAD plus 5-HTP, negative DCAD plus saline, and negative DCAD plus 5-HTP, resulting in n = 8 per group. Total calcium (tCa), ionized calcium (iCa), and feed intake were recorded. The iCa was elevated prepartum in the ?DCAD/5-HTP group compared with the other treatment groups as well as on d 0 and 1 postpartum. Although differences in tCa were not significant across the pre- or postpartum periods, tCa was numerically higher on d 0 and significantly higher on d 1 in ?DCAD/5-HTP cows compared with all other groups. Prepartum the ?DCAD/5-HTP treatment group ate less than the other treatment groups; however, postpartum dry matter intake differences were not significant. These findings demonstrate that feeding a ?DCAD diet in conjunction with 5-HTP prepartum can increase postpartum circulating iCa concentrations and therefore diminish the magnitude of hypocalcemia at the time of parturition.     

Effects of prepartum dietary cation-anion difference on aspects of peripartum mineral and energy metabolism and performance of multiparous Holstein cows

The objectives of this study were to determine the effect of decreasing dietary cation-anion difference [DCAD; (Na⁺ + K⁺) ? (Cl^? + S^2?)] of the prepartum diet on aspects of mineral metabolism, energy metabolism, and performance of peripartum dairy cows. Multiparous Holstein cows (n = 89) were enrolled between 38 and 31 d before expected parturition and randomized to treatments in a completely randomized design (restricted to balance for previous 305-d mature equivalent milk production, parity, and body condition score) at 24 d before expected parturition. Treatments consisted of a low-K ration without anion supplementation [CON; n = 30, DCAD = +18.3 mEq/100 g of dry matter (DM)]; partial anion supplementation to a low-K ration (MED; n = 30, DCAD = +5.9 mEq/100 g of DM); and anion supplementation to a low-K ration to reach a targeted average urine pH between 5.5 and 6.0 (LOW; n = 29, DCAD = ?7.4 mEq/100 g of DM). Cows were fed a common postpartum diet and data collected through 63 d in milk. Urine pH (CON = 8.22, MED = 7.89, and LOW = 5.96) was affected quadratically by decreasing prepartum DCAD. A linear relationship between urine pH and urine Ca:creatinine ratio was observed (r = ?0.81). Plasma Ca concentrations in the postpartum period (d 0 to 14; CON = 2.16, MED = 2.19, and LOW = 2.27 mmol/L) were increased linearly with decreasing prepartum DCAD. A treatment by parity (second vs. third and greater) interaction for postpartum plasma Ca concentration suggested that older cows had the greatest response to the low DCAD diet and older cows fed LOW had decreased prevalence of hypocalcemia after calving. A quadratic effect of decreasing DCAD on prepartum DMI was observed (CON = 13.6, MED = 14.0, and LOW = 13.2 kg/d). Milk production in the first 3 wk postpartum was increased linearly with decreasing DCAD (CON = 40.8, MED = 42.4, and LOW = 43.9 kg/d) and DMI in this period also tended to linearly increase (CON = 20.2, MED = 20.9, and LOW = 21.3 kg/d). Overall, effects on intake and milk yield analyzed over wk 1 to 9 postpartum were not significant. This study demonstrates that feeding lower DCAD diets prepartum improves plasma Ca status in the immediate postpartum period and results in increased DMI and milk production in the 3 wk after parturition. Compared with no anion supplementation or lower levels of anion supplementation, greater improvements were observed with the lower DCAD feeding strategy, in which an average urine pH of 5.5 to 6.0 was targeted.     

Effects of prepartum dietary cation-anion difference and source of vitamin D in dairy cows: Health and reproductive responses

The objectives of the experiment were to evaluate the effects of feeding diets with distinct dietary cation-anion difference (DCAD) levels and supplemented with 2 sources of vitamin D during the prepartum transition period on postpartum health and reproduction in dairy cows. The hypotheses were that feeding acidogenic diets prepartum would reduce the risk of hypocalcemia and other diseases, and the benefits of a negative DCAD treatment on health would be potentiated by supplementing calcidiol compared with cholecalciferol. Cows at 252 d of gestation were blocked by parity (28 nulliparous and 52 parous cows) and milk yield within parous cows, and randomly assigned to 1 of 4 treatments arranged as a 2 × 2 factorial, with 2 levels of DCAD, positive (+130 mEq/kg) or negative (?130 mEq/kg), and 2 sources of vitamin D, cholecalciferol or calcidiol, fed at 3 mg for each 11 kg of diet dry matter. The resulting treatment combinations were positive DCAD with cholecalciferol (PCH), positive DCAD with calcidiol (PCA), negative DCAD with cholecalciferol (NCH), and negative DCAD with calcidiol (NCA), which were fed from 252 d of gestation to calving. After calving, cows were fed the same lactation diet supplemented with cholecalciferol at 0.70 mg for every 20 kg of dry matter. Blood was sampled 7 d before parturition, and at 2 and 7 d postpartum to evaluate cell counts and measures of neutrophil function. Postpartum clinical and subclinical diseases and reproductive responses were evaluated. Feeding a diet with negative DCAD eliminated clinical hypocalcemia (23.1 vs. 0%) and drastically reduced the incidence and daily risk of subclinical hypocalcemia, and these effects were observed in the first 48 to 72 h after calving. The diet with negative DCAD tended to improve the intensity of oxidative burst activity of neutrophils in all cows prepartum and increased the intensity of phagocytosis in parous cows prepartum and the proportion of neutrophils with killing activity in parous cows postpartum (58.5 vs. 67.6%). Feeding calcidiol improved the proportion of neutrophils with oxidative burst activity (60.0 vs. 68.7%), reduced the incidences of retained placenta (30.8 vs. 2.5%) and metritis (46.2 vs. 23.1%), and reduced the proportion of cows with multiple diseases in early lactation. Combining the negative DCAD diet with calcidiol reduced morbidity by at least 60% compared with any of the other treatments. Cows with morbidity had lower blood ionized Ca and serum total Ca concentrations than healthy cows. Treatments did not affect the daily risk of hyperketonemia in the first 30 d of lactation. Despite the changes in cow health, manipulating the prepartum DCAD did not influence reproduction, but feeding calcidiol tended to increase the rate of pregnancy by 55%, which reduced the median days open by 19. In conclusion, feeding prepartum cows with a diet containing a negative DCAD combined with 3 mg of calcidiol benefited health in early lactation.     

Short communication: Temporal effect of feeding potassium carbonate sesquihydrate on milk fat in lactating dairy cows fed a fat-depressing diet

A lactation study with 10 multiparous dairy cows in early lactation, with an average of 64 days in milk (standard deviation = 37), were used to evaluate how quickly milk fat concentration would change when potassium carbonate sesquihydrate was abruptly added to the diet. The experiment had 3 periods. In period 1 (d 0 to 7) all cows were fed the same basal (control) diet with 1.8% soy oil, dry basis; in period 2 (d 8 to 28) 5 cows received the control diet, whereas the other 5 cows received the control diet plus 0.59% of added K with K carbonate sesquihydrate; and in period 3 (d 29 to 42) all 10 cows received the control diet. The control diet was formulated for a dietary cation-anion difference (DCAD), calculated as Na + K ? Cl ? S, of 37.7 mEq/100 g of dry matter (DM), 1.74% of DM as K, and 5.7% long-chain fatty acids (DM%), which included 1.8% of DM as soybean oil. Period 1 was used as a covariate. In period 2, d 8 to 28, 5 cows remained on the control diet whereas 5 cows were fed with the control diet plus K carbonate sesquihydrate (DCAD+ diet; DCAD of 54.3 mEq/100 g DM and 2.33% of DM as K). After feeding the DCAD+ diet, we noted a difference in milk fat concentration from 3.9 to 4.3% within 72 h. Over the 21 d of period 2, the DCAD+ diet resulted in significantly greater milk fat percentage from 4.0 to 4.3%, lactose from 4.74 to 4.82%, and fat efficiency in the form of fat in milk divided by fat in DMI from 1.27 to 1.49, without affecting dry matter intake (DMI), milk protein concentration, solids-not fat concentration, 3.5% fat-corrected milk, and protein efficiency in the form of protein in milk divided by protein in DMI. In period 3 (d 29–42), all cows were again fed the control diet, resulting in a tendency for greater milk fat concentration, significantly greater lactose concentration, and fat efficiency in the form of fat in milk divided by fat in DMI for the cows having received the DCAD+ diet during period 2. In conclusion, the abrupt addition of K carbonate sesquihydrate resulted in a greater milk fat concentration and tended to maintain the greater concentration after cessation of K carbonate sesquihydrate feeding.     

Effect of a metabolically created systemic acidosis on calcium homeostasis and the diurnal variation in urine pH in the non-lactating pregnant dairy cow

Reducing the dietary cation-anion difference (DCAD) has been shown to be an effective means of preventing parturient paresis in confinement systems where cows are offered a total mixed ration containing DCAD-reducing mineral compounds (anionic salts). Such a supplementation strategy is not possible in cows being group fed forages precalving, and little is known about the effect of supplementing these cows with large amounts of anionic salts twice daily.Eight non-lactating, pregnant Holstein-Friesian cows were allocated to two levels of DCAD (-20 and +18 meq/100 g DM) for 24 d, with an intensive Ca balance undertaken in metabolism stalls following a 2-week acclimatization to diet. The basal diet was 3 kg DM of crushed barley and 7 kg DM of pasture-hay. Urine and faeces were collected separately, weighed daily for 5 d and analysed for Ca content. Urinary Ca, creatinine and hydroxyproline concentration and plasma Ca concentration were determined during the period of the balance study. The diurnal pattern in urine and rumen pH was determined over 2 d. Decreasing DCAD reduced (P<0.001) the pH of urine, and increased (P<0.05) Ca absorption. Plasma Ca concentration was not affected by DCAD, and DCAD did not affect the output of urinary hydroxyproline, a marker of bone resorption. Twice-daily supplementation of anionic salts was sufficient to reduce the pH of blood and increase gastrointestinal Ca absorption. There was no diurnal variation in the pH of urine, suggesting that time of sampling to determine efficacy of DCAD in reducing systemic pH was not important.     

Effects of altering dietary cation-anion difference on calcium and energy metabolism in peripartum cows

Our objective was to determine the effects of varying dietary cation-anion differences (DCAD: meq[(Na + K) - (Cl + S)]/100 g of dry matter) in prepartum diets on Ca, energy, and endocrine status prepartum and postpartum. Holstein cows (n = 21) and heifers (n = 34) were fed diets with varying amounts of CaCl2, CaSO4, and MgSO4 to achieve a DCAD of +15 (control), 0, or -15 meq/100 g of dry matter for the last 24 d before expected calving. Dietary Ca concentration was increased (by CaCO3 supplementation) with decreasing DCAD. Plasma ionized Ca concentrations prepartum and at calving in both cows and heifers increased with reduced DCAD in the diet. At calving, plasma ionized Ca concentration was 3.67, 3.85, and 4.35 for cows and 4.44, 4.57, and 4.62 mg/dl for heifers fed diets containing +15, 0, and -15 DCAD, respectively. All heifers had normal concentrations of plasma ionized Ca (>4 mg/dl) at calving. Also at calving, plasma concentrations ofparathyroid hormone and calcitriol were less in cows and heifers fed diets containing reduced DCAD, but the plasma concentration of hydroxyproline was not affected by diet. Prepartum dry matter intake, energy balance, and body weight gains were lower and concentration of liver triglyceride was higher for heifers but not cows fed the -15 DCAD diet. Also, nonesterified fatty acids the last week prepartum were positively correlated with liver triglyceride for heifers but not cows. Feeding of anionic salts plus CaCO3 to reduce DCAD to -15 and increase Ca in prepartum diets prevents hypocalcemia at calving in cows, but decreases prepartum dry matter intake and increases the concentration of liver triglyceride in heifers. That heifers maintained calcium homeostasis at calving regardless of diet but ate less when fed the -15 DCAD diet suggests that they should not be fed anionic salts before calving.     

Meta-analysis of the effects of prepartum dietary cation-anion difference on performance and health of dairy cows

The objectives were to use meta-analytic methods to determine the effects of changes in dietary cation-anion difference (DCAD) prepartum on productive performance and health of dairy cows. The literature was systematically reviewed, searching randomized experiments with transition cows that manipulated the prepartum DCAD or experiments with acidogenic diets in which dietary Ca, P, or Mg was manipulated. Forty-two experiments, including 134 treatment means and 1,803 cows, were included in the meta-analysis. Of those, 5 experiments with 15 treatment means reported responses for 151 nulliparous cows. Data collected included the mineral composition of prepartum diets, parity group prepartum, breed, days on treatment, and means and respective measure of variance for urine pH, dry matter intake (DMI), body weight, body condition, productive performance, concentrations of minerals and metabolites in blood, and incidence of diseases. Mixed effects meta-analyses were conducted weighting by the inverse of standard error of the means squared to account for the precision of each experiment. Models include the effects of DCAD, parity group prepartum, interaction between DCAD and parity group, and other covariates that showed significance in univariable analysis. Final models were selected based on parsimony and model fit. Reducing the prepartum DCAD reduced intake prepartum but improved intake postpartum in both parity groups. Interactions between DCAD and parity group occurred for yields of milk, fat-corrected milk (FCM), fat, and protein because reducing the DCAD improved those responses in parous cows; however, reducing the DCAD either had no effect on yields of milk and protein or reduced the yield of FCM and fat in nulliparous cows. The resulting equations from the statistical models predicted that reducing the DCAD from +200 to ?100 mEq/kg would increase blood total Ca on the day of calving from 1.86 to 2.04 ± 0.05 mM, DMI postpartum 1.0 kg/d, and milk yield 1.7 kg/d in parous cows. The increased concentrations of blood total Ca at calving and postpartum explained the marked reduction in risk of milk fever in parous cows with a reduction in DCAD. As the DCAD decreased, the risk of retained placenta and metritis also decreased, resulting in fewer disease events per cow in both nulliparous and parous cows. Dietary concentrations of Ca, P, or Mg prepartum had no effect on DMI or yields of milk and FCM; however, increasing dietary Ca within the study range of 0.16 to 1.98% of dry matter tended to increase the risk of milk fever in parous cows regardless of DCAD fed. Collectively, results support the recommendation of prepartum acidogenic diets to result in a negative DCAD to parous cows with improvements in lactation performance and reduced risk of diseases; however, the range of DCAD fed did not allow for detection of an optimum value for postpartum performance. On the other hand, despite improvements in blood concentrations of Ca and reduction in uterine diseases with a reduction in DCAD fed to nulliparous cows, productive performance was either depressed or unaffected and the limited number of experiments did not provide sufficient evidence for a recommended DCAD for this group of cows.     

Potassium carbonate as a cation source for early-lactation dairy cows fed high-concentrate diets

Previous studies reported that addition of K₂CO₃ to high-concentrate diets improved milk fat synthesis, although the mechanism is yet to be established. The objective of the current experiment was to investigate the effects of dietary cation-anion difference (DCAD), cation source, and buffering ability of the mineral supplement on rumen biohydrogenation of fatty acids and production performance in dairy cows fed a high-concentrate diet. Thirty-five early-lactation Holstein cows (25 multiparous ruminally fistulated and 10 primiparous nonfistulated) were used in a randomized complete block design (7 blocks) with 33-d periods, including a 5-d pre-treatment collection period used as a covariate. Diets were (1) control, a basal diet [47% nonfibrous carbohydrates, DCAD (Na + K – Cl – S) = 65 mEq/kg of dry matter (DM)] containing 40% forage (including 60% corn silage) and 60% concentrate, (2) K₂CO₃ (control + K₂CO₃, 1.8% of DM, DCAD = 326 mEq/kg of DM), (3) KHCO₃ (control + KHCO₃, 2.6% of DM, DCAD = 324 mEq/kg of DM), (4) KCl (control + KCl, 2.0% of DM, DCAD = 64 mEq/kg of DM), and (5) Na₂CO₃ (control + Na₂CO₃, 1.4% of DM, DCAD = 322 mEq/kg of DM). Pre-planned orthogonal contrasts were used to assess the effects of K₂CO₃ (control vs. K₂CO₃), buffering ability (K₂CO₃ vs. KHCO₃), DCAD (K₂CO₃ vs. KCl), and cation type (K₂CO₃ vs. Na₂CO₃). Supplementing K₂CO₃ in a high-concentrate diet did not improve milk fat yield or 4% fat-corrected milk yield. Milk fat concentration was greater in cows fed K₂CO₃ compared with control (4.03 vs. 3.26%). Milk yield tended to decrease (34.5 vs. 38.8 kg/d) and lactose yield decreased in cows fed K₂CO₃ as compared with KCl (1.64 vs. 1.87 kg/d). Milk fat concentration of trans-10 18:1 was increased when cows were fed Na₂CO₃ as compared with K₂CO₃. A positive relationship was observed between concentrations of anteiso 15:0 and trans-10,cis-12 18:2 in milk fat from cows receiving K₂CO₃. Milk Na concentration was increased, whereas milk Cl was decreased with K₂CO₃ as compared with KHCO₃ or KCl. A positive relationship was established between milk Cl concentration and milk yield (R² = 0.34) across all dietary treatments. Cation-anion difference (Na + K – Cl – S) in ruminal fluid was increased with K₂CO₃ as compared with control or KCl. Blood pH tended to decrease in cows fed KCl compared with K₂CO₃. Our results suggest that mineral supplementation tends to affect milk and milk fat synthesis and that factors other than DCAD, potassium ion, or buffer ability may be implicated. The variations observed in mineral composition of milk suggest an allostatic process to maintain an ionic equilibrium in mammary epithelial cells in response to mineral composition of the diet.     

Effects of injectable calcitriol on mineral metabolism and postpartum health and performance in dairy cows

Objectives were to determine the effects of an injectable formulation of calcitriol on Ca concentration, risk of clinical diseases, and performance in dairy cows. Cows were blocked by lactation number (1 vs. >1) and calving sequence and, within block, assigned randomly within 6 h of calving to receive subcutaneously vehicle only (CON, n = 450) or 200 (CAL200, n = 450) or 300 μg of 1α,25-dihydroxyvitamin D₃ (CAL300, n = 450). Cows were fed the same acidogenic diet prepartum. Blood was sampled before treatment administration and again during the first 11 d postpartum and analyzed for concentrations of ionized Ca (iCa), total Ca (tCa), Mg (tMg), and P (tP), β-hydroxybutyrate, carboxylated osteocalcin (cOC), and undercarboxylated osteocalcin (uOC). Cows were evaluated for diseases in the first 60 d postpartum. Reproduction and survival were monitored for the first 300 d postpartum. Calcitriol increased concentration of blood iCa (CON = 1.12 vs. CAL200 = 1.23 vs. CAL300 = 1.27 mM), plasma tCa (CON = 2.29 vs. CAL200 = 2.44 vs. CAL300 = 2.46 mM), and plasma tP (CON = 1.72 vs. CAL200 = 2.21 vs. CAL300 = 2.28 mM), and differences were observed during the first 5 d postpartum for iCa and tCa, and the first 7 d postpartum for tP. Concentrations of tMg were lower in calcitriol-treated cows than in CON cows (CON = 0.81 vs. CAL200 = 0.78 vs. CAL300 = 0.75 mM), and differences were observed during the first 5 d postpartum. Calcitriol increased plasma concentrations of cOC (CON = 14.5 vs. CAL200 = 23.0 vs. CAL300 = 19.8 ng/mL) and uOC (CON = 1.6 vs. CAL200 = 3.4 vs. CAL300 = 2.6 ng/mL). Prevalence of subclinical hypocalcemia was less in calcitriol-treated cows (CON = 19.0 vs. CAL200 = 4.7 vs. CAL300 = 9.3%); however, benefits on health were only observed in overconditioned cows (n = 270/1,350). Calcitriol reduced incidence of retained placenta (CON = 14.3 vs. CAL200 = 5.1 vs. CAL300 = 5.9%), puerperal metritis (CON = 12.7 vs. CAL200 = 6.1 vs. CAL300 = 2.5%), and morbidity (CON = 72.1 vs. CAL200 = 57.4 vs. CAL300 = 56.9%) in cows with BCS greater than 3.50, but no benefit on health was observed in cows with BCS equal to or less than 3.50 at parturition. Milk yield did not differ among treatments. Pregnancy at first AI did not differ, but pregnancy rate after the first AI was slower for calcitriol-treated cows because of reduced insemination rate and pregnancy per AI. We found that CAL200 reduced death but increased culling in cows without calving problems. Collectively, results indicate that treatment with calcitriol at parturition was effective in improving concentrations of iCa, tCa, and tP, which reduced the risk of hypocalcemia. Pregnancy rate was reduced by calcitriol treatment, and benefits on health performance were limited to overconditioned cows. Thus, treatment of all cows is not supported, and proper identification of cohorts of cows that benefit from postpartum interventions that increase blood calcitriol or calcium is needed.