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.

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.

Association of passive immunity and genetic composition, health, and performance of tropical dairy calves.

This retrospective cohort study aimed to identify risk factors for the failure of transfer of passive immunity (FPI) in preweaned dairy calves, explore its associations with morbidity, mortality, genetics, and determine a standardized cut-off point for FPI. Analyzing data from 6011 calves, factors such as sire predicted transmitted ability for milk (PTA), birth season, retained placenta (RP), total serum protein concentration (TSP), morbidity (neonatal calf diarrhea - NCD, bovine respiratory disease - BRD, tick-borne disease - TBD), mortality, and average daily weight gain (ADG) were considered. The calves were categorized into predominantly Gyr (PG) and predominantly Holstein (PH) genetic composition groups. Multivariate mixed logistic regression revealed optimal TSP cut-off points for predicting morbidity (7.6 g/dL) and mortality (6.9 g/dL). PH calves exhibited 1.35 times higher odds of FPI and 1.48 times greater odds of disease. Calves from multiparous cows and those born to dams with RP had increased FPI odds. Disease prevalence was 53%, with 41% NCD, 18% BRD, and 10% TBD. Season, parity, PTA, and birth weight were associated with disease odds, though FPI was not a reliable predictor. The mortality percentage was 6%, with PH calves and those with a positive PTA having higher odds. The ADG was 0.64 kg, and FPI-affected calves gained less weight. The study compared and identified various risk factors that potentially impact calf immunity. However, the use of a standardized cut-off point for FPI assessment was not effective in predicting morbidity and mortality at this specific farm.

Use of sexed sorted semen for fixed-time artificial insemination or fixed-time embryo transfer of in vitro-produced embryos in cattle.

Artificial insemination and in vitro embryo production are powerful tools for disseminating superior genetic qualities and improving the reproductive performance of dairy and beef cattle. In conjunction with these biotechnologies, sexed-sorted semen has been used to obtain offspring of a predetermined sex. This study compared the pregnancy rates obtained using in vitro fertilization/timed embryo transfer (IVF/TET) and timed artificial insemination (TAI), both performed using sexed-sorted (Y-chromosome-bearing) semen obtained from the same bull. For the in vitro embryo production, the ovaries of 250 Nelore cows with known histories were collected in the slaughterhouse and used for IVF. After evaluation of the recipients (IVF/TET group; n = 974), the resultant embryos were transferred to the females with corpus luteum (n = 822). The pregnancy-related data for this group were compared with those for the TAI group (n = 974). Ultrasonography was performed at 60 days to determine the pregnancy status and confirm the sex of the fetus. A total of 2008 oocytes produced 1050 embryos, with 52% of them reaching the blastocyst stage. The pregnancy rate and the accuracy in determining the fetal sex were 35.4% (345/974) and 95.07% (328/345), respectively, for the IVF/TET group and 30% (293/974; P < 0.05) and 94.88% (278/293), respectively, for the TAI group. In the present study, we concluded that male calves could be better obtained using IVF/TET rather than TAI; therefore, this strategy can be considered to increase the pregnancy rate of beef cattle.