Recipient Organization
UNIV OF MINNESOTA
(N/A)
ST PAUL,MN 55108
Performing Department
College of Veterinary Medicine
Non Technical Summary
Transition cows (3 weeks before to 3 weeks after calving) present metabolic changes that resemble diabetes. In transition cows,the peripheral insulin resistance is important to increase availability of glucose for insulin-independent uptake of glucose by themammary gland for colostrogenesis and lactogenesis. However, during the transition period, reduced feed intake results inadipose tissue mobilization, increased concentrations of non-esterified fatty acid (NEFA), and reduced insulin like growth factor(IGF)-1 concentrations. These metabolic alterations predispose transition cows to immunosuppression that is characterized byreduced number and compromised function of polymorphonuclear leukocytes (PMNL). Thus, transition cows are at greater riskof infectious diseases such as metritis (infection and inflammation of the uterus). Given the cost of metritis (U$ 358/case;Overton and Fetrow, 2008), the US dairy cow population (9 million), and the incidence of metritis (25%; Chapinal et al., 2011;Martinez et al., 2012), the estimated cost of metritis to the USA dairy industry is approximately U$ 800 million per year. In arecent experiment, treatment of transition cows with somatotropin (rbST) during the transition period increased PMNL count andactivity, increased IgG concentration, reduced beta-hydroxybutyrate (BHB) concentration, and reduced incidence of metritis in65%. The evaluation of PMNL and hepatic gene expression will provide insights on the mechanisms through which rbSTimproved metabolic and immune parameters of transition cows and will provide valuable information for the development of newpreventative strategies in food producing animals.
Animal Health Component
70%
Research Effort Categories
Basic
30%
Applied
70%
Developmental
(N/A)
Goals / Objectives
Objectives of the current experiment are to evaluate the effects of rbST treatment during the transition period on PMNLexpression of genes related to inflammation and metabolism and liver expression of genes related to inflammation, metabolism,and the somatotropic axis. A secondary objective of the current experiment is to determine the effects of rbST during thetransition period on PMNL count and functionality. The hypothesis of the current experiment is that rbST treatment during thetransition period modulates gene expression of blood PMNL and liver and improves immune response and metabolism oftransition cows.
Project Methods
Animals - Parous cows (n = 15/treatment) at 255 ± 3 d of gestation will be balanced for parity (2 vs > 2nd), previous lactation milkyield, body condition score (BCS), and body weight and will be randomly assigned to one of two treatments.Treatments - Control cows will not be treated and rbST125 cows will receive 125 mg of rbST every 7 d from -21 to 28 d relativeto calving. The chosen dose is the dose that resulted in the most improved immune response and metabolic status according toour pilot experiment (Silva et al., 2013; Silva et al., 2014).Polymorphonuclear leukocyte count, function, and gene expression - Blood sampled weekly from -21 to 28 d relative to calvingwill be used to assess ex vivo PMNL phagocytosis and oxidative burst, PMNL expression of adhesion molecules (L-selectin andβ-integrins) using flowcytometry (Silva et al., 2013). Samples collected weekly from -21 to 28 d relative to calving will be used forhemogram. Also, PMNL isolated from samples collected -21, -7, 0, 7, and 21 d relative to calving will be used to assess geneexpression (Table 1; Moyes et al., 2014).Anti-body production - Cows will be injected with 1 mg of ovalbumin at -21, -7, and 7 d relative to calving to assess circulatingconcentration of IgG anti-ovalbumin weekly from -21 to 28 d relative by ELISA (Silva et al., 2013b).Somatotropic axis, metabolites, acute phase protein, chemokine, and cytokines - Blood sampled weekly from -21 to 28 d relativeto calving will be used for determination of concentrations of GH and IGF-1, metabolites (glucose, NEFA and BHB), acute phaseprotein (serum amyloid A, haptoglobin), tumor necrosis factor-α, and interleukin-1, interleukin-6, interleukin-8, and interleukin-10(Mendonça et al., 2013).Liver biopsy, gene expression, and metabolites - Cows will have liver biopsied at -21, -7, 0, 7, and 21 d relative to calving toassess gene expression (Table 2; McCarthy, 2009; Lucy et al., 2008; Rhoads et al., 2004). Liver samples collected at -21, -7, 0,7, and 21 d relative to calving will also be used to determine glycogen, triglycerides, and total lipids.Statistical analysis - Continuous variables measured repeatedly will be analyzed by ANOVA for repeated measures using theMIXED procedure of SAS using cow as the random effect. All data will be evaluated for its distribution. Data not normallydistributed will be log transformed before statistical analysis. Effect of treatment on gene expression will be evaluated as foldchange in expression of genes between treatments and over time.