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ARS Home » Plains Area » Lubbock, Texas » Cropping Systems Research Laboratory » Livestock Issues Research » Research » Research Project #430455

Research Project: Effect of OmniGen-AF Supplementation on the Stress and Metabolic Responses of Dairy Cows Exposed to Heat Stress

Location: Livestock Issues Research

Project Number: 3096-32000-008-12-T
Project Type: Trust Fund Cooperative Agreement

Start Date: Jan 1, 2015
End Date: Dec 31, 2019

The Objective during Amendment 1 will revised to read as follows: The specific objective of this experiment is to determine if feeding NutraGen for a period of 35 days will alter the metabolic response to a Glucose Tolerance Test and Insulin Sensitivity Test in feedlot heifers. Original Objective: The objective of this collaborative research project is to evaluate the potential beneficial effects of supplementing dairy cows with a yeast-based product prior to being exposed to a neurohormone-induced stress challenge while the cows are maintained in either a thermal neutral environment or in a heat stress environment. Physiological, endocrine and immune parameters will be evaluated for potential alterations associated with supplementation of the yeast-based product. This will be a collaborative project among scientists from the ARS' Livestock Issues Research Unit, the University of Arizona, and Prince Agri Products, Inc.

The Scope of Work during Amendment 1 will revised to read as follows: The scope of work is similar to the scope of work in the existing agreement in that ARS scientists will be responsible for conducting intensive blood sample collections from cattle from indwelling jugular catheters. Additionally, ARS scientists will be responsible for conducting a glucose tolerance test and an insulin sensitivity test on 32 head of feedlot heifers. Specifically, at 0900 on the day of the study, 32 heifers will be administered 0.5 mL/kg body weight of a 50% dextrose solution. At 1400, heifers will be administered 0.1 IU bovine insulin per kg BW. Blood samples will be collected at -60, -45, -30, -15, 0, 10, 20, 30, 45, 60, 90, 120, and 150 minutes relative to each challenge. Original Scope of Work: Twelve head of dairy cows will be obtained from the University of Arizona Dairy Farm and transported to the environmentally controlled rooms on campus. Cows will be provided a control diet (n = 6 cows) or a diet containing the yeast-based product (OmniGen-AF, n = 6 cows). All cows will be maintained in thermal neutral rooms and allowed to adapt to these facilities for at least 4 days. After the adaptation period, all cows will be fitted with indwelling jugular catheters and rectal temperature monitoring devices. The following day, all cows will be exposed to a neurohormone-induced stress challenge and blood samples will be collected for 10 hours. The next day, all cows will be exposed to a pituitary derived-hormone challenge and blood samples collect for another 10-hour period. The following day, the temperature will be ramped up in the rooms to induce a heat stress on the cows. After 2 days of heat stress exposure, all cows will be subjected to the same two stress challenges as those conducted in the thermal neutral conditions. For all stress challenge periods, blood samples will be collected at 30-minute intervals for 2 hours prior to the stress challenge (i.e., baseline), and for 8 hours after the stress challenge to determine if supplementing with the yeast-based product alters the physiological, endocrine, or immune responses to the challenges. Serum will be isolated from all blood samples and stored until analyzed for various stress hormones and metabolic substrates by scientists at the University of Arizona. Blood samples collected for complete blood cell counts will be processed immediately after collection using a ProCyte Dx Hematology Analyzer.