Recipient Organization
UNIV OF WISCONSIN
21 N PARK ST STE 6401
MADISON,WI 53715-1218
Performing Department
Dairy Science
Non Technical Summary
Physiology and metabolism of the female mammal is well-established in order to adapt to the demands of gestation and lactation. Calcium is a critical mineral for both growth of the neonate and is the primary mineral in milk. Research in a variety of mammalian species has demonstrated that calcium decreases at the onset of lactation in order to trigger a negative feedback mechanism in which bone calcium can be mobilized to support synthesis of milk in combination with maternal homeostasis. Dairy cows produce milk in quantities far beyond what is required by the neonate, therefore making them more susceptible to hypocalcemia. Research to date has yet to determine what the "normal" decrease in calcium concentrations around the time of parturition is, and what the best predictive measures are, pre and post-partum, for determining optimal calcium status in periparturient dairy cows. This knowledge will allow us to make recommendations for farmers on how to determine if a cow's calcium homeostasis is compromised and also make recommendations for dietary management of dairy cows prepartum to prevent hypocalcemia postpartum.USDA-NIFA has prioritized improving animal health and production and generating a more economically viable animal production system. This is goal is directly linked to the National Priority for Global Food Security and Food Availability: Livestock and Poultry. Our research on hypocalcemia in dairy cows directly impacts dairy cow health and longevity, which is critical for milk production. Our research is also critical for to the Wisconsin State Priorities aligned sustainable agricultural production systems to improve food safety and security by understanding basic life processes in animal systems in order to manage biotic systems for human use. Furthermore, our research aligns with performing studies that further research and development related to agricultural processes with the potential to enhance the productivity and quality of livestock and food in a sustainable manner.
Animal Health Component
10%
Research Effort Categories
Basic
90%
Applied
10%
Developmental
0%
Goals / Objectives
Physiology and metabolism of the female mammal is well-established in order to adapt to the demands of gestation and lactation. Calcium is a critical mineral for both growth of the neonate and is the primary mineral in milk. The major goals of this proposal are: 1) Determine how the magnitude of Ca decline at the onset of lactation has ongoing effects on production, mineral metabolism of multiparous dairy cows; 2) Determine how a low or high calcium supplementation in combination with a negative DCAD diet effects postpartum calcium homeostasis.There are several strategies that are currently used in the dairy industry that are focused on improving postpartum calcium homeostasis in dairy cows. The most common include feeding a dietary cation-anion difference (DCAD) prepartum, manipulating dietary Ca supplementation (pre and postpartum), feeding low Ca diets prepartum, feeding of dietary Ca binders prepartum, and administration of Ca postpartum. The gaps in this proposal that will be addressed are the following: 1) What is the normal decrease in Ca at the time of parturition in dairy cows to maintain optimal postpartum metabolic homeostasis? and 2) What is the optimal level of dietary Ca supplementation in combination with a negative DCAD diet to support postpartum ionized Ca concentrations?
Project Methods
Experiment 1 Approach-Thirty-two multiparous Holstein cows (N=8 per treatment group) will be blocked by parity and previous 305d milk production and randomly assigned to one of four treatments in a randomized complete block design. Cows enrolled on the study will calve in blocks. Treatments will be arranged in a 2 x 2 factorial, with two levels DCAD [DCAD mEq/kg = (Na+ + K+) - (Cl- + S-)], negative (-120 mEq/kg) or positive (+120 mEq/kg), with 0.45% Ca inclusion in the diet using CaCO3 to adjust if necessary. At parturition cows will receive intravenous saline or calcium gluconate for 24 hours. Daily feed intake will be recorded and twice weekly sampling of feeds, composited weekly by feed type, will be analyzed. Postpartum cows will be fed the lactating herd diet. An n=8 will be used for each treatment group for a total of 32 cows. This sample size was chosen based on a power analysis using total Ca concentrations as the response variable. We expect to see a 0.2 mM change in total Ca concentrations, with a standard deviation of 0.25, resulting in a power of 0.8.Starting on -21 d relative to estimated parturition, cows will be placed on their dietary treatment. Daily samples will start to be collected on -28 d relative to parturition at 3 hours post feeding through 30 d postpartum. Whole blood, serum, plasma, and urine will be collected for analysis. Beginning 10 days prior to expected calving date whole blood, serum, plasma, urine samples will be taken every 6 hours until parturition. Immediately prior to start of parturition blood samples will be taken. Jugular indwelling catheters will be placed in cows 4 days prior to expected parturition date.At the onset of parturition (stage 1 parturition-repeated standing and lying, stage 2 paturition-presence of the sac in the vaginal area) blood will be drawn and analyzed for Ca every 20 minutes. Post parturition cows will immediately receive infusions of intravenous Kreb's ringer buffer (CON) or calcium gluconate (TRT). Treated cows will be intravenously infused with calcium gluconate to achieve normocalcemia (2.1 mM total Ca, 1.05 mM ionized Ca). CON cows rate of infusion will be matched to that of the TRT group to control for fluid administration between the groups. During infusion cows will be blood sampled from their jugular vein every 30 minutes. Cow side analysis of ionized Ca will occur to determine calcemic status of individual cows. Whole blood, serum, plasma, and urine will be taken every 6 hours during the infusion period starting at the immediate end of parturition and following out till d3 postpartum. Milk samples and yield will be collected at each milking for the immediate 3 days postpartum.After the initial 3d postpartum, samples will be collected every 3 days until 30 days in milk. Whole blood, serum, plasma, and urine will be collected and analyzed. Dry matter intake will be recorded until 30 days in milk. Daily milk yield, weekly milk samples and health incidences will be recorded for the first 100 days in milk. Entire lactation (305d) milk production will be recorded.Blood, urine, and milk analysesBlood samples will be analyzed for ionized calcium (iCa), total calcium (tCa), phosphorous (P), magnesium (Mg), parathyroid hormone (PTH), parathyroid hormone related protein (PTHrP), estrogen, serotonin, 1, 25(OH2D3) vitamin D, insulin-like growth factor 1 (IGF1), calcitonin, osteocalcin (carboxylated and uncarboxylated), glucose, beta-hydroxybutyrate (BHBA), cholesterol, non-esterified fatty acid, creatinine, interleukins 6 and-10 (IL-6; IL-10), ceruplasmin, insulin, glucagon, leptin, and adiponectin concentrations. All measurements will be conducted as previously described in Laporta et al., 2015, Weaver et al., 2016; Slater et al. 2018; Rodney et al., 2018. These various hormones and metabolites have been previously determined to be critical for the maintenance of calcium homeostasis (Ducy and Karsenty, 2010; Karsenty and Oury, 2010; Karsenty and Ferron, 2012; DeGaris and Lean, 2008; Lean et al., 2013; Rodney et al., 2018).Urine samples will be analyzed for pH, deoxypyridinoline, creatinine, tCa, P, and Mg concentrations as described in Weaver et al., 2016 and Slater et al., 2018. Milk samples will be analyzed for total milk solids, fat, protein, somatic cell count, lactose, solids non-fat, and milk urea nitrogen by Ag Source. Total Ca concentrations in milk will be analyzed as described in Weaver et al., 2016.Experiment 2 Approach-This experiment aims to demonstrate that feeding a negative DCAD diet in combination with high dietary Ca prepartum increases post-calving ionized Ca concentrations compared to negative DCAD in combination with low dietary calcium prepartum. To this end, we will perform a randomized complete block design with a 2x2 factorial arrangement of treatments in which there will be four treatment groups: 1) Positive DCAD diet (+130 meEq/kg) fed for 21 d pre-calving (PDCADlowCa) and 0.45% dietary calcium, 2) positive DCAD diet plus 2.0% dietary calcium (PDCADhiCa), 3) negative DCAD diet (-130mEq/kg) fed for 21 days pre-calving with 0.45% dietary calcium (NDCADlowCa), and 4) negative DCAD diet plus 2.0% dietary calcium (NDCADhiCa). Thirty-two multiparous Holstein cows will be blocked by anticipated calving date then randomly allocated to one of the four treatments to yield 8 cows per treatment. An n=8 will be used for each treatment group for a total of 32 cows. This sample size was chosen based on a power analysis using ionized Ca concentrations as the response variable. We expect to see a 0.2 mM change in ionized Ca concentrations, with a standard deviation of 0.25, resulting in a power of 0.8. Blood and urine samples will be taken at -9, -7, -5, -3, -1, 0, 1, 2, 3, and every 3 d until d 30 of lactation. Mammary gland biopsies will be collected on days 1, 10, 20, and 30 postpartum. Milk samples will be collected on the same days as the post-calving blood samples. Milk yield and feed intake will be recorded daily, and feed samples will be collected weekly for dry matter analysis and nutrient analysis as described in Experiment 2. Whole blood will be analyzed for 5-HT. Serum harvested from blood will be analyzed for total Ca, ionized Ca, PTH and ICTP (Weaver et al., 2016; Hernandez-Castellano et al., 2018). Plasma harvested from blood will be analyzed for PTHrP. Urine samples will be analyzed for total Ca and DPD concentrations as described in experiment 2. Urine pH will also be monitored prepartum to ensure diet acidification. Milk samples postpartum will be analyzed for total Ca concentrations using atomic absorption (Weaver et al., 2016). Total RNA will be extracted from mammary gland samples and real-time quantitative PCR will be performed for the following genes: PTHrP, PMCA2, ORAI1, SPCA1, SPCA2, CaSR, TPH1, cyclin D1, alpha-lactalbumin, beta-casein, and beta-lactoglobulin as described in Slater et al., 2018.Efforts- Data will be presented at the American Dairy Science Association Meeting, Producer Meetings, Nutrition Conferences, and results will be published in the appropriate peer review journals (Journal of Dairy Science, PLoS One, etc.).