Document Type

Dissertation - University Access Only

Award Date

2002

Degree Name

Doctor of Philosophy (PhD)

Department / School

Dairy Science

First Advisor

Arnold R. Hippen

Abstract

The nutritional status of a host can affect the length and severity of an illness caused by a viral infection. An associative study was conducted to evaluate the consequences of elevated intermediary metabolites, body condition score, and fatty liver on the immune function in periparturient dairy cattle. The effects of fatty liver and ketosis on immune function were assessed by antigen-specific lymphocyte proliferation and circulating serum neutralmrtion titers to bovine viruses, such as bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine herpesvirus-1 (BHV-1) and parainfluema-3 (PI3), in periparturient dairy cattle. The data suggests that elevated plasma concentrations of nonesterified fatty acids (NEFA) were negatively correlated to circulating memory activity and also negatively correlated to serum neutralizing antibodies against BRSV and PI3. Plasma Phydroxybutyrate (BHBA) was also negatively correlated with circulating serum neutralizing titers against PI3. We have demonstrated that individual products of fat metabolism, such as NEFA and BHBA, diminished immune responsiveness to viral antigens. VI To evaluate acidosis, ketosis, and ketoacidosis without the additive effects that fatty liver impose on immune parameters, acidosis-inducing diets were fed to four Holstein steers using a Latin square design. Diets were supplemented with I) high grain diets to induce lactic acidosis 2) anionic salts to induce mineral acidosis and 3) butylenes glycol to induce a ketonemia. A negative relationship existed between venous pH and proliferative response to BVDV and BHV-1. In comparison, the maximum circulating memory response, after stimulation of BRSV in vitro, occurred in lymphocytes isolated from steers fed butylene glycol the BHBA inducing diet. Nonspecific antigen driven lymphocyte proliferation to Staphylococcus aureus exotoxin (SEB), a measured overall T cell proliferative capacity, was depressed by all of the acidosis-inducing diets. Decreased response to SEB by each of the acidosis inducing diets may explain an increased susceptibility of periparturient dairy cows to infection. The objective of a study consisting of in vitro evaluation of circulating T cell memory to viral antigens was to establish an effective model for predicting the influences of metabolic disorders such as acidosis and ketoacidosis. Varying concentrations of BHBA added to media under defined pH conditions ranging from 6.8 to 8.0. The proliferative response of lymphocytes in response to BVDV had a tendency to be positively correlated with increasing BHBA concentration. The BHBA and pH interactions tended to negatively decrease the nonspecific antigen driven proliferative responses after stimulation with SEB and specific antigen driven proliferation after stimulation with PB. The data suggests that the combination of BHBA and pH may have a compounding affect on lymphocyte proliferation. The experiments conducted on viral propagation demonstrated that a differential effect existed between viruses and the type of acidotic diet or in vitro culture utilized. As a result, certain viruses may be more prevalent in particular production situations, such as animals raised feedlot scenario compared dairy herds raised in confinement. Ketosis is a complex metabolic disorder, that encompass increases in NEFA and BHBA. The immunosuppressive effects observed may be more a result of increased concentration of NEFA than BHBA.

Library of Congress Subject Headings

Dairy cattle -- Virus diseases
Viral antigens
Immune response
Metabolism -- Disorders

Publisher

South Dakota State University

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Rights Statement

In Copyright