Mechanisms by which feeding synthetic zeolite A and dietary cation-anion difference diets affect 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 use 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 diet with negative dietary cation-anion difference (-DCAD), or a positive-DCAD diet (CON) during the close-up period on peripartal mineral dynamics and hormones involved in calcium metabolism. To this end, 121 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/d; 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 (d 0), and on d 1, 2, 3, 6, 9, 12, 15, 18, 21, 35, and 49 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 were 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 phosphorus (P), increased fecal water-extractable phosphate, and the highest blood calcium concentrations pre- and postpartum. Parathyroid hormone was unaffected by diet but was increased at parturition in all treatments. Serotonin concentrations were increased in -DCAD and XZ cows compared with CON during the prepartum period. Our data indicate that the XZ group's improvement in blood Ca concentrations pre- and postpartum is most likely 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 affect 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 diet with low dietary cation-anion difference (DCAD) or a diet with synthetic zeolite A, to multiparous Holstein cows during the close-up period on dry matter intake (DMI) and energy metabolism, as well as to evaluate colostrum and milk production. A total of 121 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), or a diet containing sodium aluminum silicate zeolite (XZ; +278 mEq/kg, fed at 3.3% dry matter, targeting 500 g/d; 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, the Netherlands). All cows received the same postpartum diet. Blood and urine samples were collected daily beginning 14 d before parturition (d -14) until parturition (d 0), 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 the 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. 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 lactation or greater 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 cows in their third lactation or greater fed XZ produced the most milk. These data suggest that feeding XZ prepartum may improve colostrum quality and milk yield in mature cows, and does not affect energy metabolism.