Recipient Organization
UNIVERSITY OF MISSOURI
(N/A)
COLUMBIA,MO 65211
Performing Department
Veterinary Medicine & Surgery
Non Technical Summary
Early postpartum dairy cows undergo acute physiological changes to accommodate the transition from late pregnancy to early lactation. During this period there is a shift in nutrient partitioning away from the pregnancy and towards the mammary gland. Energetic demands for lactation are greater than pregnancy so cows experience a negative energy balance during early lactation. The metabolism of non esterified fatty acids (NEFA) derived from adipose tissue becomes an important source of energy. Ketones bodies [primarily β hydroxybutyrate (BHB)] derived from incomplete oxidation of fatty acids are a source of energy for some tissues but can be toxic if concentrations are too high (clinical or subclinical ketosis). A number of studies have demonstrated adverse effects of elevated BHB on the reproductive performance of postpartum cows. Most of these studies evaluated dairy cows during the transition period (the first month postpartum) when NEFA and BHB concentrations are greatest. These studies have led to cut-points for blood BHB concentration that can be used by clinicians early postpartum to the assess the risk for clinical and subclinical disease that affect productivity and fertility later postpartum. In preliminary work at Foremost Dairy (University of Missouri) we found that cows with elevated BHB at the time of first breeding (> 60 d postpartum) were also at risk for infertility at the time of first artificial insemination (AI). Our results were unexpected because the dogma is the elevated BHB are only found early postpartum. The aim of this project is to conduct a larger study in which we test blood BHB concentrations at the time of the first AI in a number of cows on a commercial dairy farms and Foremost Dairy. We will collect baseline data for BHB at first AI and determine the relationship between BHB at first AI and the probability of pregnancy. These data can be used to establish a threshold (cut-point) for BHB measured at the time of first AI. To accomplish our objectives, blood BHB will be measured in 400 cows immediately before first postpartum AI. Plasma will be harvested and additional analyses will be done for BHB (lab assay), glucose, and NEFA at the University of Missouri, Department of Animal Sciences.Testing for BHB in either the blood or milk of early postpartum cattle is a widely accepted practice. Clinical cases of ketosis are relatively rare on modern dairies. Subclinical ketosis, however, is more common and its presence poses a great threat to productivity if it is not diagnosed and nutritional management is not changed. This study will explore the implications of elevated ketones later postpartum (at the time of first AI). This is a time when cows are not routinely tested. If a relationship between BHB at first AI and pregnancy outcome is found and cut-points for infertility can be established then we believe that testing programs will be widely adopted by the dairy industry. Herds with elevated BHB at first breeding would be advised of the associated risk and management changes could be implemented to reduce BHB and increase fertility to AI. A large improvement in reproductive performance would be realized from a relatively simple and inexpensive BHB testing program that invokes appropriate changes in management.
Animal Health Component
50%
Research Effort Categories
Basic
25%
Applied
50%
Developmental
25%
Goals / Objectives
The objectives of this study are to measure β-hydroxybutyrate (BHB) concentrations at first insemination and assess its utility as a marker for the success or failure of the pregnancy outcome. We will then determine a BHB threshold (cut-point) to identify cows at risk for infertility based on circulating BHB at the time of first artificial insemination (AI).Specific AimsI. Evaluate the utility of blood BHB concentrations at the time of the first AI as a marker for fertility in dairy cowsII. Establish a threshold (cut-point) for BHB at the first AI to predict pregnancy outcome and identify cows at risk for infertility.
Project Methods
Four hundred lactating Holstein dairy cows from commercial farms in Missouri, as well as the University of Missouri Foremost Dairy will be used in the proposed study. To achieve the number of cows proposed, multiple visits to the farms are expected. All cows participating in the study will be from commercial farms and Foremost Dairy, within the farms, the cattle will be under similar feeding, management and breeding protocol.The commercial farms are using a Double Ovsynch estrus synchronization timed AI protocol. All first insemination occurs on one day of the work week. This facilitates the implementation of this trial because we can visit the farm on a single day and collect blood from first insemination cows prior to AI.On the day of first insemination (65-75 days postpartum), 10 mL of blood will be sampled from coccygeal vessels into an evacuated tube containing EDTA. Blood BHB will be measured immediately using a handheld meter (PortaBHB; Portacheck, Moorestown, NJ) and BHB testing strips. The samples will then be placed on ice shortly after collection and transported back to the laboratory. At the laboratory, plasma will be harvested and frozen for subsequent laboratory analysis of plasma BHB, non-esterified fatty acids and glucose.Artificial insemination will be performed by farm personnel. Pregnancy examination will be performed using ultrasonography by the farm's herd veterinarian or the Theriogenology faculty, in the case of Foremost Dairy, at 35-42 days post-insemination, and redone at 65-75 days post-insemination to account for pregnancy loss. For the statistical analyses, cows will be considered pregnant when both pregnancy exams yield positive outcomes. Percentage of abortion (cows that had positive outcome on first pregnancy check, but negative on the second test) will also be assessed. Milk production and health status data will be retrieved using the farm's dairy software program.Statistical AnalysisData will be analyzed by mixed model analysis of variance from SAS (version 9.4; SAS Institute Inc., Cary, NC) using the fixed effects of pregnancy outcome after two ultrasound checks (positive or negative), abortion (positive followed by negative), parity (primiparous or multiparous), milk components (somatic cell count, protein, and fat contents) and milk production (high, moderate or low). A prediction equation for the probability of pregnancy using a logistic regression model of SAS (SAS Institute Inc.) from blood BHB concentrations on the insemination day will be used to calculate the probability of pregnancy. Receiver operating characteristic (ROC) analyses will be conducted using SigmaPlot (Systat Software Inc., San Jose, CA) to determine the threshold for BHB at the day of first insemination to predict subsequent pregnancy outcome.