Dietary Cation-anion Difference Research Articles

Periparturient Mineral Metabolism: Implications to Health and Productivity.

Mineral metabolism, in particular Ca, and to a lesser extent phosphorus (P) and magnesium (Mg), is altered with the onset of lactation because of extensive irreversible loss to synthesize colostrum and milk. The transient reduction in the concentration of Ca in blood, particularly when it lasts days, increases the risk of mineral-related disorders such as hypocalcemia and, to a lesser extent, hypophosphatemia. Although the incidence of clinical hypocalcemia can be reduced by prepartum dietary interventions, subclinical hypocalcemia remains prevalent, affecting up to 60% of the dairy cows in the first 3 d postpartum. More importantly, strong associations exist between hypocalcemia and increased susceptibility to other peripartum diseases and impaired reproductive performance. Mechanistic experiments have demonstrated the role of Ca on innate immune response in dairy cows, which presumably predisposes them to other diseases. Hypocalcemia is not related to inadequate Ca intake as prepartum diets marginal to deficient in Ca reduce the risk of the disease. Therefore, the understanding of how Ca homeostasis is regulated, in particular how calciotropic hormones such as parathyroid hormone and 1,25-dihydroxyvitamin D3, affect blood Ca concentrations, gastrointestinal Ca absorption, bone remodeling, and renal excretion of Ca become critical to develop novel strategies to prevent mineral imbalances either by nutritional or pharmacological interventions. A common method to reduce the risk of hypocalcemia is the manipulation of the prepartum dietary cation-anion difference. Feeding acidogenic diets not only improves Ca homeostasis and reduces hypocalcemia, but also reduces the risk of uterine diseases and improves productive performance. Feeding diets that induce a negative Ca balance in the last weeks of gestation also reduce the risk of clinical hypocalcemia, and recent work shows that the incorporation of mineral sequestering agents, presumably by reducing the absorption of P and Ca prepartum, increases blood Ca at calving, although benefits to production and health remain to be shown. Alternative strategies to minimize subclinical hypocalcemia with the use of vitamin D metabolites either fed prepartum or as a pharmacological agent administered immediately after calving have shown promising results in reducing hypocalcemia and altering immune cell function, which might prove efficacious to prevent diseases in early lactation. This review summarizes the current understanding of Ca homeostasis around parturition, the limited knowledge of the exact mechanisms for gastrointestinal Ca absorption in bovine, the implications of hypocalcemia on the health of dairy cows, and discusses the methods to minimize the risk of hypocalcemia and their impacts on productive performance and health in dairy cows.

Exploring the cause of reduced production responses to feeding corn dried distillers' grains in lactating dairy cows

An experiment was conducted to identify the factors that cause reduced production of cows fed a diet with high corn distiller's grains with solubles (DDGS). We hypothesized that the factors could be high S content in DDGS which may directly (S toxicity) or indirectly [dietary cation-anion difference (DCAD)] cause reduced production. We also hypothesized that high polyunsaturated fatty acids (PUFA) in DDGS could be another major factor. In a randomized complete block design, 60 lactating cows (15 primiparous and 45 multiparious; average ± SD at the beginning of the trial: milk yield, 44.0 ± 6.9 kg/d; DIM, 123 ± 50; BW, 672 ± 82 kg) were blocked and cows in each block were randomly assigned to one of the following treatments: SBM [4.7% fatty acids (FA), 0.22% S, and 178 mEq/kg DM of DCAD], a diet containing soybean meal as the main protein source; DG, SBM replacing mainly soybean byproducts and supplemental fat with DG at 30% dietary DM (4.7% FA, 0.44% S, and 42 mEq/kg DM of DCAD); SBM+S, SBM with sodium bisulfate for additional dietary S (4.8% FA, 0.37% S, and 198 mEq/kg DM of DCAD); SBM+CO, SBM with corn oil (4.7% FA, 0.23%, and 165 mEq/kg DM of DCAD); and DG+DCAD, DG with increased DCAD (4.7% FA, 0.40% S, and 330 mEq/kg DM of DCAD). Due to the limited tie stalls, the blocks of 1 to 6 started the experiment first as phase 1 and the rest of the blocks as phase 2 started the experiment after phase 1. All cows were fed the SBM diet for 10 d as a covariate period followed by the experimental period for 35 d. Data were analyzed using the PROC MIXED of SAS, block and phase were random effects and treatments, repeated wk, and interaction were fixed effects. There was an interaction of wk by treatment for DMI. While milk yield did not change, milk fat concentration tended to decrease (2.78 vs. 3.34%) for DG compared with SBM. Dry matter, OM, NDF, and CP digestibilities were lower when cows were fed the DG diet compared with SBM. Additionally, cows fed DG had lower blood concentrations of HCO3-, base excess, and tCO2 compared with SBM. The SBM+S diet did not affect production, nutrient digestibility, or blood parameters when compared with SBM. The SBM+CO diet decreased milk fat concentration and yield compared with SBM. The DG+DCAD diet tended to increase milk fat yield and concentration (1.24 vs. 1.47 kg/d; 2.78 vs. 3.37%) and increased ECM (40.9 vs. 45.1 kg/d) compared with DG but did not improve nutrient digestibility. However, blood HCO3-, base excess, and tCO2 were greater for DG+DCAD compared with DG. In conclusion, the indirect role of S-, altering DCAD, along with the high PUFA content in DDGS appears to be the factors causing reduced production responses to a high DDGS diet. Increasing DCAD to 300 mEq/kg DM in a high DDGS diet can be a feeding strategy to alleviate the reduced production responses.

MECHANISMS BY WHICH FEEDING SYNTHETIC ZEOLITE A AND DIETARY CATION ANION DIFFERENCE DIETS IMPACT MINERAL METABOLISM IN MULTIPAROUS HOLSTEIN COWS: PART I

The periparturient period is characterized by the increased demand for calcium (Ca) in dairy cows. This has resulted in the utilization of several different prepartal nutritional strategies to prevent hypocalcemia postpartum. The objective of our study was to determine the effects of feeding synthetic zeolite A (XZ), a negative dietary cation-anion difference (DCAD) diet, or a positive DCAD diet (CON) during the close-up period on peripartal mineral dynamics and hormones involved in calcium metabolism. To this end, one hundred and 21 multiparous Holstein cows, blocked by lactation number and expected due date were enrolled at 254 d of gestation and randomly assigned to 1 of 3 prepartum diets: CON (+190 mEq/kg; n = 40), -DCAD (-65 mEq/kg; n = 41), or a diet supplemented with sodium aluminum silicate (XZ; +278 mEq/kg, fed at 3.3% DM, targeting 500 g/day; n = 40; Protekta Inc.). Blood, urine, and saliva samples were collected from enrollment until parturition, with data analyzed and presented beginning 14 d before parturition (D-14) until parturition (D0), and on D1, D2, D3, D6, D9, D12, D15, D18, D21, D35, and D49 postpartum to assess mineral and hormone dynamics. Total fecal collections were performed in a subset of 8 cows per treatment group to assess fecal mineral loss. Data was analyzed as a randomized complete block design in SAS. Cows fed XZ and -DCAD had higher blood Ca concentrations compared with CON fed cows, with XZ fed cows exhibiting the highest blood Ca concentrations pre and postpartum. Cows fed XZ had decreased blood and salivary phosphorous (P), increased fecal water extractable phosphate (WEP), and the highest blood calcium concentrations pre and postpartum. Parathyroid hormone (PTH) was unaffected by diet but was increased at parturition in all treatments. Serotonin concentrations were increased in -DCAD and XZ fed cows compared with CON during the prepartum period. Our data indicate that XZ's improvement in blood Ca concentrations pre and postpartum most likely is regulated by a dietary P restriction. Taken together, these data suggest that XZ and -DCAD diets improve postpartum calcium metabolism, however, they appear to work through different mechanisms.

MECHANISMS BY WHICH FEEDING SYNTHETIC ZEOLITE A AND DIETARY CATION ANION DIFFERENCE DIETS IMPACT FEED INTAKE, ENERGY METABOLISM, AND MILK PERFORMANCE: PART II.

The objectives of this study were to assess the effects of feeding 2 different diets, a low dietary cation-anion difference (DCAD) or a diet with synthetic zeolite A to multiparous Holstein cows during the close-up period on DMI and energy metabolism, as well as evaluate colostrum and milk production. A hundred and 21 multiparous Holstein cows, blocked by lactation number and expected parturition date were enrolled at 254 d of gestation and randomly assigned to 1 of 3 dietary treatments: control (CON; +190 mEq/kg; n = 40), negative DCAD (DCAD, -65 mEq/kg; n = 41; Ultra Chlor; Vita Plus, Lake Mills, WI, USA), or a diet containing sodium aluminum silicate zeolite (XZ; +278 mEq/kg, fed at 3.3% DM, targeting 500 g/day; n = 40; X-Zelit, Protekta Inc., Lucknow, ON, Canada/Vilofoss, Graasten, Denmark). Prepartum DMI was measured daily using Insentec Roughage Intake Control (RIC) gates (RIC System, Holofarm Group, Netherlands). All cows received the same postpartum diet. Blood and urine samples were collected daily beginning 14 d before parturition (D-14) until parturition (D0), and on 1, 2, 3, 6, 9, 12, 15, 18, 21, 35, and 49 d postpartum. Colostrum collected within 6 h of parturition, weighed, and based on samples Brix value, IgG concentrations, and nutrient composition were analyzed. Prepartum, cows fed XZ diet had decreased DMI (11.70 ± 0.26, 13.88 ± 0.26, and 13.45 ± 0.25 kg/d for XZ, CON, and DCAD respectively) and lower rumination (487 ± 8.1, 531 ± 8.3, and 527 ± 8.5 min for XZ, CON, and DCAD respectively) compared with CON and DCAD fed cows. However, rumination was not different postpartum due to treatment. No prepartum or postpartum differences were observed for glucose or BHB concentrations in blood between dietary treatments. Colostrum collected from cows fed XZ had the highest IgG concentrations (91.10 ± 2.63, 78.00 ± 2.63, and 78.90 ± 2.63 mg/mL for XZ, CON, and DCAD, respectively), but yield did not differ between dietary treatments. Additionally, cows in their third or greater lactation fed XZ had the highest milk production (51.0 ± 1.1 kg) during the first 49 d in milk. This study demonstrates that despite a decrease in DMI and rumination in cows fed XZ prepartum, blood BHB concentrations were not altered. Additionally, cows fed XZ had higher colostral IgG concentrations and 3+ lactation cows fed XZ produced the most milk. These data suggest that feeding XZ prepartum may improve colostrum quality and improve milk yield in mature cows, and does not impact energy metabolism.

Long-term liming changes pasture mineral profile

There is limited information on changes of pasture mineral concentrations over the long-term in response to liming. A long-term field experiment was conducted to assess the influence of lime application on (a) changes in pasture mineral composition over time; and (b) key pasture mineral concentrations and ratios important to animal health. Perennial and annual pastures with or without lime application were sampled annually over 12 years and analysed for macro- and micro-minerals. Mineral ratios and indices were calculated to assess the potential impact on animal health. Liming increased the concentrations of calcium, sodium and silicon, but decreased the concentrations of micro-nutrients including copper, zinc and manganese. The same trend was found in both annual and perennial pastures although there were some fluctuations between years. Liming increased the calcium:phosphorus ratio and the dietary cation–anion difference but reduced the tetany index on both annual and perennial pastures. These findings suggest a potential benefit to improve animal health outcomes for some disorders on the limed pastures. However, the reduced concentrations of some trace elements following liming potentially decreases antioxidant capacity and requires further research.

Influence of Dietary Cation-Anion Differences (DCAD) on Nutrient Intake, Milk Yield and Metabolic Parameters of Transition Buffaloes

The study was divided into 2 phases. During 1st phase, 20 pre-partum buffaloes were divided into two groups, given -100 (high negative; HN) and -50 (low negative; LN) mEq/kg of dry matter (DM) diets. In the second phase, +200 (low positive; LP) and +400 (high positive; HP) mEq/kg of DM diets were formulated for postpartum buffaloes. Buffaloes that received LN DCAD were divided into 2 groups (LN-LP and LN-HP), and those that received HN DCAD were also divided into 2 groups (HN-LP and HN-HP). In the first phase, the group fed the HN DCAD diet had significantly lesser DM, nutrient intake, and urine pH (p<0.05) but higher ME intake and ADF digestibility. Also, higher serum phosphorus levels (p<0.05), fewer cases of hypocalcemia and ketosis, and a relatively smaller decrease in body weight were reported with the HN group. In the second phase, DM, organic matter, and NDF intakes were higher (p<0.05) in HN-HP and LN-LP groups, whereas ME intake and nutrient digestibility were higher in HN-LP and LN-HP (p<0.05). Daily milk, solid not fat (SNF), fat, protein, lactose yields, and plasma total protein, urea, and cholesterol concentrations were the highest in the HN-HP group (p<0.05), but the highest fat content and fat yield were recorded in the HN-LP group (p<0.05). Better efficiency of milk production and the lowest cases of hypocalcemia and ketosis were observed for both groups. In conclusion, for transition buffaloes, the HN and LN DCAD (-100 and +200 mEq/kg of DM, respectively) diets showed a beneficial impact.

High dietary cation and anion difference formulation increased heat dissipation in non-lactating goats fed at high ambient temperature.

In our previous study, we observed that a high dietary cation and anion difference (DCAD) of 40 mEq/kg dry matter (DM) in the diets of lactating dairy goats increased heat dissipation. In the present study, we believe that the level of DCAD fed to non-lactating and non-pregnant goats was twice as high as that fed to lactating goats in our previous study. This increase could have resulted in a greater water balance due to increased intake of water and unchanged urinary excretion. Therefore, this study aimed to determine the behavioral and heat dissipation effects of a dietary shift from low to high DCAD levels in dairy goats under tropical conditions. Seven non-lactating and non-pregnant crossbred goats were used in this study. All animals were initially fed a low DCAD (15 mEq/100 g DM) diet from days 0-6 and then switched to a high DCAD (89 mEq/100 g DM) diet from day 7 (high DCAD-7) to day 18 (high DCAD-18). The results revealed that a high DCAD increased DM intake from days 13-18 (p < 0.05). The larger daily meal size associated with the high DCAD-18 group was due to increased daytime meal sizes, not nighttime when compared to the low DCAD group. Dietary cation and anion difference supplementation did not affect daily water intake; however, drinking patterns differed between the low DCAD group and the high DCAD-7 group from 07:00 to 09:00 and during nighttime. Similarly, daily urine volume was unaffected by DCAD supplementation, but urinary patterns differed between the low DCAD and high DCAD-18 groups. The daily water balance remained unchanged across all treatments, yet, a higher morning water balance was observed in the high DCAD group. The high DCAD diet led to an increase in respiration rate and rectal temperature compared to the low DCAD diet. The observed eating, drinking, and urinary patterns collectively suggested that high DCAD supplementation mitigates the effects of heat stress in non-lactating goats fed at high ambient temperatures.

The Effect of Variation in Dietary Cation-Anion Difference on Calcium Status, Blood Metabolites and Rumen Activity during the Transition Period of Holstein Dairy Cows

A negative dietary cation-anion difference (DCAD) induces a compensated metabolic acidosis, stimulating calcium (Ca) absorption and mobilization before calving, thereby decreasing clinical and subclinical hypocalcemia postpartum. The study was designed to determine the effects of varying pre- and postpartum DCAD diets on serum total calcium, ionized calcium, blood and ruminal fluid metabolites, and milk production in prepartum and postpartum Holstein cows. Fifty-four multiparous dry Holstein cows n= 54, were enrolled in a completely randomized block experimental design at 29 days prior to expected parturition through 86 days in milk. A 3 x 2 factorial arrangement of treatments was utilized. Three DCAD levels were fed precalving (0, -120 and -200 mEq/kg DM), n=18 cows per treatment and two DCAD levels were fed post calving (+200 and +400 mEq/kg DM), n=27 cows per treatment. Prepartum urine pH was lower for cows fed -200 DCAD compared with those fed -120 or 0 DCAD. Postpartum urine pH was higher for cows fed +400 mEq/kg compared to cows fed +200 mEq/kg DCAD. Prepartum serum total calcium, ionized calcium, and hydroxyproline was highest for cows fed -200 DCAD compared to those fed -120 and 0 DCAD. Parathyroid hormone was highest for cows fed 0 DCAD compared to those fed -120 and -200 DCAD. Prepartum dry matter intake (DMI) was lower for -200 and -120 DCAD compared with 0 DCAD. Postpartum DMI was not different among treatments. Pre- and postpartum DCAD treatments did not affect total milk yield or milk fat, percentage of milk protein not affected by different pre-and postpartum DCAD levels. Prepartum anionic diets lowered urine pH and parathyroid hormone and raised serum hydroxyproline, resulting in improved Ca availability after parturition. Postpartum blood metabolites were unaffected in cows given positive DCAD (+200 and +400 mEq/kg DM). Calves born to cows fed low DCAD had no change in calf bieth weight. Colostrum amount and IgG concentrations were unaffected by treatments. No effects of pre-or postpartum DCAD treatments were observed for milk yield and fat-corrected milk. Feeding prepartum an acidogenic diet improved postpartum Ca status in multiparous Holstein cows.

Comparison of two different anionic supplements and a low calcium diet fed to transition cows prepartum on DM intake, mineral homoeostasis and performance.

This study evaluates the effects of two rations with a positive dietary cation-anion difference (DCAD) and varying Ca content and two anionic diets on mineral homoeostasis and performance in early lactation cows. For this purpose, 48 pregnant dairy cows stratified for mature equivalent milk production, parity, body condition score (BCS), and BW were randomly assigned to four treatment groups and fed the following rations during the last 3weeks of gestation: LC: low Ca (0.24% Ca, 1.14% K, DCAD: +86mEq/kg DM), HC: high Ca (1.23% Ca, 1.17% K, DCAD: +95mEq/kg DM), AS: Anionic salt (1.21% Ca, 1.21% K, DCAD: -112mEq/kg DM, and SC: SoyChlor (1.28% Ca, 1.16% K, DCAD: -115mEq/kg DM). After parturition, all animals were fed a common postpartum diet. Data were collected until 21days in milk. Urinary pH was significantly decreased with the AS and SC treatment in comparison to the LC and HC groups. The highest prepartum DM intake (DMI) was found in the LC group, while DMI in AS cows was lowest. Postpartum, DMI was significantly greater in LC and SC cows than in animals fed the HC and AS rations. Prepartum serum concentrations of Ca, P, and Mg as well as postpartum serum concentrations of P and Mg did not differ, while postpartum Ca was lower in the HC group, especially 24 and 48h after parturition. The greatest energy-corrected milk (ECM) yield was observed in cows fed the LC ration prepartum. Interestingly, milk protein production was lower in SC cows compared to LC, HC and AS. This study indicates that a ration containing a restricted Ca content fed prepartum is as suitable as a low DCAD diet to improve Ca balance without compromising DMI and performance.

Influence of prepartum dietary cation-anion difference and the magnitude of calcium decline at the onset of lactation on mineral metabolism and physiological responses

The onset of lactation is characterized by substantially altered calcium (Ca) metabolism; recently, emphasis has been placed on understanding the dynamics of blood Ca in the peripartal cow in response to this change. Thus, the aim of our study was to delineate how prepartum dietary cation-anion difference (DCAD) diets and the magnitude of Ca decline at the onset of lactation altered blood Ca dynamics in the periparturient cow. Thirty-two multiparous Holstein cows were blocked by parity, previous 305-d milk yield and expected parturition date, and randomly allocated to either a positive (+120 mEq/kg) or negative (-120 mEq/kg) DCAD diet from 251 d of gestation until parturition (n = 16/diet). Immediately after parturition cows were continuously infused for 24 h with (1) an intravenous solution of 10% dextrose or (2) Ca gluconate (CaGlc) to maintain blood ionized (iCa) concentrations at ∼1.2 mM (normocalcemia) to form 4 treatment groups (n = 8/treatment). Blood was sampled every 6 h from 102 h before parturition until 96 h after parturition and every 30 min during 24 h continuous infusion. Cows fed a negative DCAD diet prepartum exhibited a less pronounced decline in blood iCa approaching parturition with lesser magnitude of decline relative to positive DCAD-fed cows. Cows fed a negative DCAD diet prepartum required lower rates of CaGlc infusion to maintain normocalcemia in the 24 h postpartum relative to positive DCAD-fed cows. Infusion of CaGlc disrupted blood Ca and P dynamics in the immediate 24 h after parturition and in the days following infusion. Collectively, these data demonstrate that prepartum negative DCAD diets facilitate a more transient hypocalcemia and improve blood Ca profiles at the onset of lactation whereas CaGlc infusion disrupts mineral metabolism.

Influence of Prepartum and Postpartum Dietary Cation-Anion Difference (Dcad) On Milk Production and Some Physiological Parameters of Dairy Shami Goats

Influence of Prepartum and Postpartum Dietary Cation-Anion Difference (Dcad) On Milk Production and Some Physiological Parameters of Dairy Shami Goats

Negative dietary cation-anion difference and amount of calcium in prepartum diets: Effects on urine and serum minerals

Negative dietary cation-anion difference (DCAD) diets fed prepartum induce a compensated metabolic acidosis, which stimulates metabolic Ca flux before calving and decreases clinical and subclinical hypocalcemia after calving. Effects of low or high dietary Ca in these diets are unclear. Our objective was to determine the effects of inducing a prepartum metabolic acidosis and the amount of dietary Ca on urinary mineral excretion and serum mineral concentrations during the transition period in multiparous Holstein cows (n = 81). Treatment diets fed during the last 28 d before calving were (1) positive DCAD, +6 mEq/100 g of dry matter (DM), target urine pH >7.5, low dietary Ca (0.40% DM; CON); (2) negative DCAD, −24 mEq/100 g of DM, target urine pH 5.5 to 6.0, low dietary Ca (0.40% DM; ND); or (3) negative DCAD, −24 mEq/100 g of DM, target urine pH 5.5 to 6.0, high dietary Ca (2.0% DM; NDCA). Urine was sampled on −21, −14, −7, +1, +2, and +7 d relative to calving. Blood samples were collected on d −30, −21, −14, −7, −4, −2, −1, 0, 1, 2, and 4 relative to parturition. Preplanned treatment contrasts were (1) CON versus ND and NDCA, and (2) ND versus NDCA. Cows fed ND or NDCA had increased urinary volume and excretion of Ca, Cl, and SO4−2, along with decreased excretion of K. Supplementation of Ca to the acidogenic diet increased urinary excretion of Ca at d −21, but this difference lessened as cows approached parturition. Additional Ca increased prepartum urinary excretion of K and Cl. Differences in excretion decreased quickly after parturition, although urinary excretion of Cl remained greater for cows previously fed negative DCAD diets. Acidogenic diets increased serum K and Cl concentrations prepartum. Supplemental Ca decreased serum P relative to ND. During d 0 to 4, serum P and K were greater for cows fed ND or NDCA than for cows fed CON; these differences disappeared by d 4. Acidogenic diets increased serum Ca by increasing Ca flux and excretion in urine. Supplemental Ca in the acidogenic diet modestly increased Ca excretion early in the close-up period.

Epidemiology of bovine colostrum production in New York Holstein herds: Prepartum nutrition and metabolic indicators

Colostrum yield and quality are influenced by prepartum nutrition and the metabolic status of the cow; however, data considering these associations on multiple dairy farms are limited. Our objective was to identify cow-level prepartum metabolic indicators, as well as farm-level nutritional strategies associated with colostrum yield and the indicator of colostrum quality, Brix %. A convenience sample of 19 New York Holstein dairies (median: 1,325 cows; range: 620 to 4,600 cows) were enrolled in this observational study. Records for individual colostrum yield and Brix % were collected by farm personnel between October 2019 and February 2021. Farms were visited 4 times, approximately 3 mo apart, to obtain feed samples of the prepartum diets, collect blood samples from 24 pre- and postpartum cows, respectively, and determine prepartum body condition score. Feed samples were submitted for analysis of chemical composition, and particle size was determined on-farm using a particle separator. Prepartum serum samples (n = 762) were analyzed for glucose and nonesterified fatty acid concentrations. Whole blood from postpartum cows was analyzed for herd prevalence of hyperketonemia (proportion of samples with β-hydroxybutyrate ≥1.2 mmol/L). A cohort of primiparous (PP; n = 1,337) and multiparous (MPS; n = 3,059) cows calving ± 14 d of each farm visit were included in the statistical analysis. Animals calving in this period were assigned results for the close-up diet composition and herd prevalence of hyperketonemia collected from the respective farm visit. Greatest colostrum yield from PP and MPS cows was associated with moderate starch [18.6-22.5% of dry matter (DM)] and a moderate herd prevalence of hyperketonemia (10.1-15.0%). Greatest colostrum yield from MPS cows was associated with moderate crude protein (13.6-15.5% of DM) and a less severe negative dietary cation-anion difference (DCAD; >-8 mEq/100 g), whereas greatest colostrum yield from PP cows was associated with low crude protein (≤13.5% of DM). In addition, a moderate proportion of the diet with particle length ≥19 mm (15.3-19.1%) was associated with lowest colostrum yield from PP and MPS cows. Highest colostrum Brix % was associated with prepartum dietary factors of low neutral detergent fiber (≤39.0% of DM) and high proportion of the diet with particle length ≥19 mm (>19.1%). In addition, low starch (≤18.5% of DM) and low and moderate DCAD level (≥-15.9 mEq/100 g) were associated with greatest Brix % from PP cows, whereas moderate DCAD (-15.9 to -8.0 mEq/100 g) was associated with greatest Brix % from MPS cows. Prepartum serum nonesterified fatty acid concentration ≥290 µEq/L was associated with increased colostrum yield, but prepartum serum glucose concentration and body condition score were not associated with colostrum yield or Brix %. These data provide nutritional and metabolic variables to consider when troubleshooting colostrum production on farms.

Effects on rumen pH and feed intake of a dietary concentrate challenge in cows fed rations containing pH modulators with different neutralizing capacity

Forty-five Holstein lactating cows (41 ± 8.8 kg/d of milk yield, 96 ± 35.6 days in milk, and 607 ± 80.4 kg of body weight) were enrolled in this study to assess the effects of diets supplemented with sodium bicarbonate or a magnesium-based product and their corresponding differences in dietary cation-anion difference (DCAD) on rumen pH, rumen microbial population, and milk performance of dairy cattle exposed to an induced decrease in rumen pH through a dietary challenge. Cows were randomly allocated to 3 total mixed rations (TMR) differing in the type of supplement to modulate rumen pH: (1) control, no supplementation; (2) SB, supplemented with 0.82% of sodium bicarbonate with a neutralizing capacity (NC) of 12 mEq/g; and (3) MG, supplemented with 0.25% of magnesium oxide (pHix-Up, Timab Magnesium) with a NC of 39 mEq/g. Thus, SB and MG rations had, in theory, the same NC. The 3 TMR differed for control, SB, and MG in their DCAD-S (calculated considering Na, K, Cl, and S), which was on average 13.2, 21.2, and 13.7 mEq/100 g, respectively, or DCAD-Mg (calculated accounting for Mg, Ca, and P), which was 31.4, 41.2, and 35.2 mEq/100 g, respectively. The study lasted 63 d, with the first 7 d serving as a baseline, followed by a fortnightly progressive decrease of dietary forage-to-concentrate ratio (FCR) starting at 48:52, then 44:56, then 40:60, and finishing at 36:64. Individual dry matter intake (DMI) was recorded daily. Seven cows per treatment were equipped with electronic rumen boluses to monitor rumen pH. Control and SB cows consumed less dry matter (DM; 23.5 ± 0.31 kg/d) than MG cows (25.1 ± 0.31 kg/d) when fed dietary FCR of 44:56 and 40:60. Energy-corrected milk decreased from 40.8 ± 1.21 to 39.5 ± 1.21 kg/d as dietary FCR decreased, independently of dietary treatments. Rumen pH decreased and the proportion of the day with rumen pH <5.8 increased as dietary FCR decreased, and at low dietary FCR (i.e., 36:64) rumen pH was greater in MG cows than in control and SB cows. Reducing the DCAD-S from 28 to 18 mEq/100 g or the DCAD-Mg from 45 to 39 mEq/kg had no effects on DMI or milk yield. Cows supplemented with ∼62 g/d of magnesium oxide (pHix-Up) maintained a greater rumen pH and consumed more DM than cows supplemented with ∼200 g/d of sodium bicarbonate when fed a diet with low FCR.

Evaluating the inclusion of alfalfa hay in diets fed to multigravid Holstein cows in their transition to early lactation

The objectives of this study were to determine the dry matter intake (DMI), urine pH, Ca concentration in blood, Ca output in urine, and frequency of hypocalcemia in pregnant and nonlactating dairy cows consuming diets containing different hays and acidogenic products during the prepartum period. Eighty pregnant and nonlactating Holstein cows approaching their second or greater calving were fed 1 of 4 experimental diets according to a 2 × 2 factorial arrangement of treatments during the prepartum period (21 d before calving). Diets included either grass hay (GH) or alfalfa hay (AH) and calcium chloride (CL) or polyhalite (PO) as the acidogenic products. All diets had a dietary cation-anion difference (DCAD) below -190 mEq/kg of dry matter (DM). Grass hay contained 75 g/kg crude protein, 749 g/kg neutral detergent fiber, 3.6 g/kg Ca, 0.9 g/kg Na, 18.8 g/kg K, 3.8 g/kg Cl, 1.5 g/kg S, and a cation-anion difference equal to 290 mEq/kg of DM. Alfalfa hay contained 196 g/kg crude protein, 456 g/kg neutral detergent fiber, 15.2 g/kg Ca, 1.6 g/kg Na, 25 g/kg K, 7.7 g/kg Cl, 3.2 g/kg S, and a cation-anion difference equal to 292 mEq/kg of DM. Cows consuming GH tended to consume more DM than cows consuming AH (11.6 vs. 10.8 kg/d) but DMI did not differ between acidogenic products. Urine pH decreased below 6.5 for all diets, although cows consuming the GHPO diet had the highest urine pH. The concentration of Ca in plasma decreased substantially around calving but neither hay type nor acidogenic product affected it. Urinary Ca output was lowest for cows consuming the GHPO diet. No associations existed between dietary treatments and the frequencies of normocalcemia and hypocalcemia. Under the conditions of this study, in which alfalfa and grass hays had similar cation-anion differences, we concluded that the inclusion of alfalfa hay in prepartum diets does not necessarily increase the frequency of hypocalcemia. The cation-anion difference of the alfalfa hay, more than the concentration of potassium alone, may be a key determinant of whether alfalfa hay fits in a prepartum feeding program for prepartum dairy cows. Further research should explore this relationship.

Negative dietary cation–anion difference in prepartum dairy cow diets: a pragmatic study in two commercial dairy farms

Pragmatic studies, evaluating the effectiveness of an intervention under its usual conditions, are less commonly reported than the explanatory trials. For instance, the effectiveness of prepartum negative dietary cation-anion difference (DCAD) diets on inducing a compensated metabolic acidosis that promotes a higher blood Ca concentration at calving has not been frequently described under commercial farm management conditions without researchers' interference. Thus, the objectives were to study cows under commercial farm management conditions to (1) describe the daily close-up dairy cows' urine pH and fed DCAD, and (2) evaluate the association between urine pH and fed DCAD, and preceding urine pH and blood Ca at calving. A total of 129 close-up Jersey cows about to commence their ≥2nd lactation were enrolled in the study after 7 days of exposure to DCAD diets in two commercial dairy herds. Urine pH was determined daily from mid-stream urine samples from enrollment to calving. Fed DCAD was determined from feed bunk samples obtained during 29 (Herd 1) and 23 (Herd 2) consecutive days. Plasma Ca concentration was determined within 12 h after calving. Descriptive statistics were generated at the herd- and cow-level. Multiple linear regression was used to evaluate the associations between urine pH and fed DCAD for each herd, and preceding urine pH and plasma Ca concentration at calving for both herds. At herd-level, the average urine pH and CV during the study period were 6.1 and 12.0% (Herd 1) and 5.9 and 10.9% (Herd 2), respectively. At the cow-level, the average urine pH and CV during the study period were 6.1 and 10.3% (Herd 1) and 6.1 and 12.3% (Herd 2), respectively. During the study period, fed DCAD averages were -121.3 and -165.7 mEq/kg of DM and CV 22.8 and 60.6% for Herd 1 and Herd 2, respectively. No evidence of association between cows' urine pH and fed DCAD was observed in Herd 1, whereas a quadratic association was observed in Herd 2. When both herds were combined, a quadratic association was observed between the urine pH intercept (at calving) and plasma Ca concentration. Although average urine pH and fed DCAD were within recommended ranges, the high variability observed indicates that acidification and fed DCAD are not constant, and often outside the recommended ranges in commercial settings. Monitoring of DCAD programs is warranted to ensure their effectiveness under commercial settings.

Effect of dietary cation-anion difference on dry matter intake, digestibility, body weight gain, blood parameters, and carcass traits in Zandi lambs.

The dietary cation-anion difference (DCAD) has gotten much attention recently; however, there is not much evidence on organic matter digestibility, blood parameters, dry matter intake, body weight, and carcass features of male sheep fed with different DCAD diets. The effects of dietary cation-anion difference (DCAD) on these traits in male lambs under the environmental high temperatures were investigated in this study. Forty male lambs (average body weight of 39 kg) were randomly assigned to one of five treatments with eight replicates. Lambs were fed diets with DCAD levels ranging from 150 (control group) to 300, 450, 600, and 750 mEq/kg dry matter. This study lasted 100 d and used a 21-d adaptation. The results showed that the control group had the highest dry matter intake, dry matter digestibility, and crude protein digestibility (P = 0.02). Also, the lowest amount of average body weight was observed in the control group (P = 0.01). The results showed the different DCAD levels affected the statistical significance in terms of live weight, carcass weight, length and width of muscle cross section, lung weight, spleen weight, and abdominal fat (P = 0.04). As well, the highest ruminal pH was observed in the control group (P = 0.4). The results of the blood glucose parameter showed that control group had a significant effect on the blood glucose level (P = 0.04). Furthermore, the highest abdominal fat weight was observed in the control group (P = 0.04). There was no statistically significant difference between other traits, including skin weight, head weight, leg weight, carcass length, liver weight, kidney weight, heart weight, testicle weight, tail weight, rumen weight, and lactation weight. In summary, increasing DCAD in the diet could improve the production and carcass quality in lambs under environmental high temperatures.

Effect of Sugar Beet Pulp and Anionic Salts on Metabolic Status and Mineral Homeostasis during the Peri-Parturient Period of Dairy Sheep.

Sugar beet pulp is a popular by-product of sugar extraction; however, it can potentially cause depletion of Ca availability due to its oxalic content. The experiment examined the effect of sugar beet pulp and anionic salts administration during the dry period on the serum concentration of calcium, magnesium, phosphate, and potassium of dairy sheep. Eighty-seven sheep were divided into three groups (A, B, and C) according to their body condition score (BCS) and age at 40 days before the expected lambing. All groups received alfalfa hay, mixed grass straw, and a concentrate supplement. The concentrate fed to groups B and C contained sugar beet pulp. The nutritional value fed to all three groups was similar, except for Dietary Cation Anion Difference (DCAD). Animals of group A had a DCAD of +198 mEq/kg, animals of group B of +188 mEq/kg, and animals of group C were fed 20 gr/d ammonium chloride to achieve a negative DCAD (-52 mEq/kg). All groups were fed the same ration after lambing. Blood samples were collected 30 d, 20 d, 17 d, 14 d, 10 d, 7 d, and 4 d before lambing (a.p.), 6 h, 12 h, 24 h, 7 d, 10 d, and 15 d after lambing (p.p) for calcium, magnesium, phosphate, and potassium, and 30 d a.p., 7 d, and 15 d p.p. for beta hydroxybutyrate acid (BHBA) concentrations. Urine samples were also collected 20 d, 10 d, 4 d a.p., and 7 d p.p for the evaluation of pH levels. Ca levels of the control group decreased earlier and were lower at 4 d a.p. compared to those of group B and C. Additionally, the control group showed lower p values compared to group C at 20 d and 17 d a.p. P levels recovered earlier post parturition in young (age 1-1.5 years old) compared to older ewes. Group C had lower urine pH values throughout the pre-parturient period, reflecting the acidifying effect of the administered ammonium chloride, without any side effect on macromineral blood concentration. Feeding sugar beet pulp and systemic acidifying before parturition is considered safe and might even be beneficial in preventing hypocalcemia.

Effect of source and amount of vitamin D on serum concentrations and retention of calcium, magnesium, and phosphorus in dairy cows

The objectives of the experiment were to determine the effects of supplementing 2 amounts of 25-hydroxyvitamin D3 (calcidiol; CAL) compared with equal amounts of vitamin D3 (cholecalciferol; CHOL) on serum concentrations, absorptions, and retentions of Ca, Mg, and P in periparturient dairy cows. One hundred seventy-seven (133 parous and 44 nulliparous) pregnant Holstein cows were enrolled in the experiment. Cows were blocked by parity and previous lactation milk yield (parous) or genetic merit for energy-corrected milk yield (nulliparous) and assigned randomly to receive 1 or 3 mg/d of CAL or CHOL in a 2 × 2 factorial arrangement of treatments. Treatments were provided to individual cows as a top-dress to the prepartum diet from 250 d gestation until parturition. The prepartum diet had a dietary cation-anion difference of -128 mEq/kg of dry matter. All cows were fed a common postpartum diet containing 46 μg of vitamin D3/kg of dry matter without further supplementation of treatments. Concentrations of vitamin D metabolites, Ca, Mg, and P in serum were measured pre- and postpartum, in addition to total-tract digestibility and urinary excretion of Ca, Mg, and P in the prepartum period. Feeding 3 mg compared with 1 mg of CAL increased serum 25-hydroxyvitamin D3 (CAL1 = 94 vs. CAL3 = 173 ± 3 ng/mL). In comparison, the increment in serum 25-hydroxyvitamin D3 from feeding 3 mg compared with 1 mg of CHOL was small (CHOL1 = 58 vs. CHOL3 = 64 ± 3 ng/mL). Feeding CAL increased prepartum concentration of P in serum compared with CHOL (CHOL = 1.87 vs. CAL = 2.01 ± 0.02 mM), regardless of the amount fed, but neither source nor amount affected prepartum Ca or Mg in serum. Feeding CAL increased serum Ca and P for the first 11 d postpartum compared with CHOL (CHOL = 2.12 vs. CAL = 2.16 ± 0.01 mM serum Ca; CHOL = 1.70 vs. CAL = 1.78 ± 0.02 mM serum P) but the amount of vitamin D did not affect postpartum concentrations of Ca, Mg, and P in serum. Feeding CAL increased prepartum apparent digestibility of Ca compared with CHOL (CHOL = 26.6 vs. CAL = 33.5 ± 2.8%) but treatments did not affect Ca retention prepartum. Neither source nor amount of vitamin D affected Mg and P apparent digestibility, but CAL decreased the concentration of P excreted in urine during the prepartum period (CHOL = 1.8 vs. CAL = 0.8 ± 0.3 g/d). Calcidiol tended to increase the amount of Ca secreted in colostrum (CHOL = 9.1 vs. CAL = 11.2 ± 0.9 g/d) and Ca excreted in urine postpartum (CHOL = 0.4 vs. CAL = 0.6 ± 0.1 g/d) compared with CHOL. Collectively, feeding CAL at 1 or 3 mg/d compared with CHOL in the last 24 d of gestation is an effective way to increase periparturient serum P concentration and postpartum serum Ca of dairy cows fed a prepartum diet with negative DCAD.

Effect of prepartum source and amount of vitamin D supplementation on lactation performance of dairy cows

The objectives of this experiment were to determine the effects of supplementing 25-hydroxyvitamin D3 (calcidiol, CAL) compared with vitamin D3 (cholecalciferol, CHOL) at 1 or 3 mg/d in late gestation on production outcomes of dairy cows. One hundred thirty-three parous and 44 nulliparous pregnant Holstein cows were enrolled in the experiment. Cows were blocked by parity and previous lactation milk yield (parous) or genetic merit (nulliparous) and assigned randomly to receive 1 or 3 mg/d of CAL or CHOL in a 2 × 2 factorial arrangement of treatments (CAL1, CAL3, CHOL1, and CHOL3). Treatments were provided to individual cows as a top-dress to the prepartum diet from 250 d in gestation until parturition. The prepartum diet had a dietary cation-anion difference of -128 mEq/kg of dry matter. Production and disease were evaluated for the first 42 d in milk, and reproduction was evaluated to 300 d in milk. Incidence of postpartum diseases did not differ among treatments. Feeding CAL compared with CHOL increased yields of colostrum and colostrum fat, protein, and total solids, resulting in an increased amount of net energy for lactation secreted as colostrum (CHOL = 7.0 vs. CAL = 9.0 ± 0.7 Mcal). An interaction between source and amount was observed for milk yield: CAL3 increased milk yield compared with CHOL3 (CHOL3 = 34.1 vs. CAL3 = 38.7 ± 1.4 kg/d) but milk yield did not differ between CAL1 and CHOL1 (CHOL1 = 36.9 vs. CAL1 = 36.4 ± 1.4 kg/d). Concentrations of serum calcidiol on day of calving and average serum Ca from d 2 to 11 postpartum were positively associated with milk yield in the first 42 d in milk. Interactions between source and amount of vitamin D were also observed for pregnancy after first AI: the percentage of cows receiving CHOL1 and CAL3 that became pregnant was smaller than that of cows receiving CHOL3 and CAL1. However, pregnancy per AI and pregnancy by 300 d in milk did not differ among treatments. Overall, CAL3 increased milk yield compared with CHOL3, whereas in cows fed 1 mg/d (CAL1 and CHOL1), the source of vitamin D generally had no effect. The effect of CAL3 may be explained in part by serum CAL concentrations and postpartum serum Ca, which were associated with milk yield.