Effects of supplementation of grazing Nellore cows with ß-carotene and vitamins A + D3 + E + biotin on follicle diameter, oestrus, establishment of pregnancy, and foetal morphometry.

The objectives of this experiment were to evaluate the effects of supplementation of Nellore (Bos indicus) cows with ß-carotene + vitamins A + D3 + E + biotin on body condition score (BCS), oestrus, pregnancy, and foetal morphometry. Lactating cows (n = 497) from two herds were balanced for BCS and calving period [early calving (EC); late calving (LC)] and were assigned randomly to: Control (n = 251)-supplementation with a mineral supplement; and SUP (n = 246)-supplementation with the mineral supplement fed to control + ß-carotene (150 mg/day) + vitamin A (40,000 IU/day) + vitamin D3 (5000 IU/day) + vitamin E (300 mg/day) + biotin (20 mg/day). Cows were supplemented from Days -30 to 30 (Day 0 = timed artificial insemination; TAI). Pregnancy was diagnosed 30 days after TAI and foetal crown-rump distance and thoracic diameter were measured at 30 and 77 days of gestation. Cows in the SUP treatment were more likely to have BCS ≥3.0 on Day 0 (63.0 ± 3.1 vs. 60.2 ± 3.1; p < .01) and were more likely to gain BCS from Days -30 to 30 (57.7 ± 3.3 vs. 44.1 ± 3.3%; p < .01). Fewer LC cows in the SUP treatment were detected in oestrus at the time of the first TAI (Control: LC: 75.4 ± 4.4 vs. SUP: LC: 64.0 ± 5.2 vs. Control: EC: 65.3 ± 4.0 vs. SUP: EC: 71.8 ± 3.7; p = .04). There was a tendency for the SUP treatment to increase pregnancy to the first TAI (64.2 ± 3.0 vs. 56.6 ± 3.1%; p = .08). A greater percentage of SUP cows was detected in oestrus at the time of the second TAI (70.1 ± 5.0 vs. 52.3 ± 4.8%; p = .01). The SUP treatment increased pregnancy to the second TAI among LC cows (SUP: LC: 75.9 ± 8.0% vs. Control: LC: 50.0 ± 8.3% vs. Control: EC: 52.0 ± 5.9% vs. SUP: EC: 41.4 ± 6.5%; p = .02). The SUP treatment increased foetal size (crown-rump; p = .04 and thoracic diameter; p < .01) at 30 days of gestation and, despite decreasing crow-rump length at 77 days after the first TAI among EC cows (p < .01), it increased the thoracic diameter at 77 days after the first TAI independent of calving season. Our results support that pregnancy establishment and foetal growth can be improved when grazing Nellore cows are supplemented with ß-carotene and vitamins A + D3 + E + biotin.

Effect of vitamin D source and amount on vitamin D status and response to endotoxin challenge.

The objectives were to test the effects of dietary vitamin D3 [cholecalciferol (CHOL)] compared with 25-hydroxyvitamin D3 [calcidiol (CAL)] on vitamin D status and response to an endotoxin challenge. Forty-five Holstein bull calves (5 ± 2 d of age) were blocked into weekly cohorts, fed a basal diet that provided 0.25 µg/kg body weight (BW) CHOL, and assigned randomly to 1 of 5 treatments: control [(CON) no additional vitamin D], 1.5 µg/kg BW CHOL (CHOL1.5), 3 µg/kg BW CHOL (CHOL3), 1.5 µg/kg BW CAL (CAL1.5), or 3 µg/kg BW CAL (CAL3). Calves were fed milk replacer until weaning at 56 d of age and had ad libitum access to water and starter grain throughout the experiment. Treatments were added daily to the diet of milk replacer until weaning and starter grain after weaning. Measures of growth, dry matter intake, and serum concentrations of vitamin D, Ca, Mg, and P were collected from 0 to 91 d of the experiment. At 91 d of the experiment, calves received an intravenous injection of 0.1 µg/kg BW lipopolysaccharide (LPS). Clinical and physiological responses were measured from 0 to 72 h relative to LPS injection. Data were analyzed with mixed models that included fixed effects of treatment and time, and random effect of block. Orthogonal contrasts evaluated the effects of (1) source (CAL vs. CHOL), (2) dose (1.5 vs. 3.0 µg/kg BW), (3) interaction between source and dose, and (4) supplementation (CON vs. all other treatments) of vitamin D. From 21 to 91 d of the experiment, mean BW of supplemented calves was less compared with CON calves, but the effect was predominantly a result of the CHOL calves, which tended to weigh less than the CAL calves. Supplementing vitamin D increased concentrations of 25-hydroxyvitamin D in serum compared with CON, but the increment from increasing the dose from 1.5 to 3.0 µg/kg BW was greater for CAL compared with CHOL (CON = 18.9, CHOL = 24.7 and 29.6, CAL = 35.6 and 65.7 ± 3.2 ng/mL, respectively). Feeding CAL also increased serum Ca and P compared with CHOL. An interaction between source and dose of treatment was observed for rectal temperature and derivatives of reactive metabolites after LPS challenge because calves receiving CHOL3 and CAL1.5 had lower rectal temperatures and plasma derivatives of reactive metabolites compared with calves receiving CHOL1.5 and CAL3. Supplementing vitamin D increased plasma P concentrations post-LPS challenge compared with CON, but plasma concentrations of Ca, Mg, fatty acids, glucose, ß-hydroxybutyrate, haptoglobin, tumor necrosis factor-α, and antioxidant potential did not differ among treatments post-LPS challenge. Last, supplementing vitamin D increased granulocytes as a percentage of blood leukocytes post-LPS challenge compared with CON. Supplementing CAL as a source of vitamin D to dairy calves was more effective at increasing serum 25-hydroxyvitamin D, Ca, and P concentrations compared with feeding CHOL. Supplemental source and dose of vitamin D also influenced responses to the LPS challenge.

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.

Effects of feeding 25-hydroxyvitamin D3 with an acidogenic diet during the prepartum period in dairy cows: Mineral metabolism, energy balance, and lactation performance of Holstein dairy cows.

Our objective was to determine the effects of feeding 25-hydroxyvitamin D3 [25(OH)D3], or vitamin D3 (cholecalciferol) on plasma, mineral, and metabolite concentrations, mineral balance, mineral excretion, rumination, energy balance, and milk production of dairy cows. We hypothesized that supplementing 3 mg/d of 25(OH)D3 during the prepartum period would be more effective than supplementing vitamin D3 at the National Research Council (2001) levels to minimize calcium imbalance during the transition period and improve milk production of dairy cows. Forty multiparous, pregnant nonlactating-Holstein cows were enrolled in this study. Body weight, body condition score, parity, and milk yield in the previous lactation (mean ± standard deviation) were 661 ± 59.2, 3.46 ± 0.35, 1.79 ± 0.87, and 33.2 ± 6.43 kg/d, respectively. Cows were enrolled into the blocks (n = 20 for each treatment) at 30 d of the expected day of calving to receive an acidogenic diet (373 g/kg of neutral detergent fiber and 136 g/kg of crude protein, dry matter basis; -110 mEq/kg) associated with the treatments: (1) control (CTRL), vitamin D3 at 0.625 mg/d (equivalent to 25,000 IU of vitamin D3/d) or (2) 25(OH)D3 at 3 mg/d (equivalent to 120,000 IU of vitamin D3/d). All cows were fed with the base ration for 49 d after calving. Blood samples were taken on d 7, 0, 1, 2, 21, and 42, relative to calving. No effect of treatment was observed for prepartum dry matter intake or body condition score. A trend for increase of ionized Ca was observed for the cows fed 25(OH)D3, compared with the CTRL, but no effect of treatment was detected for total Ca or total P. Feeding 25(OH)D3 increased colostrum yield. The plasmatic concentration of 25-hydroxyvitamin D3 was increased with 25(OH)D3 supplementation. 25-Hydroxyvitamin D3 supplementation increased plasma glucose concentration at parturition. The postpartum dry matter intake was not influenced by treatments. Feeding 25(OH)D3 increases milk yield, 3.5% fat-corrected milk, and energy-corrected milk and improves milk yield components in early lactation. Overall, these findings suggest that 25(OH)D3 at 3 mg/d can improve the energy metabolism and lactation performance, compared with the current-feeding practice of supplementing vitamin D3 at 0.625 mg/d.

Detection and enumeration of Staphylococcus aureus from bovine milk samples by real-time polymerase chain reaction.

The aim of this study was to develop and evaluate a real-time quantitative PCR (qPCR)-based method to detect and quantify Staphylococcus aureus in bronopol-preserved milk samples from subclinical intramammary infections (IMI). Serial dilutions of milk artificially inoculated with Staph. aureus ATCC 29213 were used to establish a standard curve (cfu/mL) of the qPCR assay targeting the Staph. aureus thermonuclease-encoding gene nuc according to the strain plate count. The analytical sensitivity, specificity, and repeatability of the qPCR assay were determined. A total of 60 milk samples, collected from mammary quarters without abnormal appearance and with positive isolation of Staph. aureus, were submitted to both the qPCR protocol and Staph. aureus plate counting and results from both methods were compared. Staphylococcus aureus from bronopol-preserved, subclinical IMI milk samples were not accurately enumerated by qPCR compared with plate counting of the nonpreserved, raw milk sample. The detection limit of the qPCR protocol of inoculated Staph. aureus ATCC 29213 in bronopol-preserved milk samples was 1.04 × 10(1) cfu/mL. The qPCR protocol can be a high-throughput and rapid diagnostic assay to accurately detect Staph. aureus IMI from bronopol-preserved milk samples compared with a traditional culturing method. However, the proposed qPCR protocol is not accurate for counting of Staph. aureus in bronopol-preserved milk samples from naturally infected mammary glands.