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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

Robert J. Baer


Researchers have been attempting to utilize a more energy dense diet by using added fat sources in dairy rations to achieve increased milk production, while increasing the unsaturated fatty acid concentration of milk fat (Casper et al., 1988; Mielke and Schingoethe, 1981; Palmquist and Jenkins, 1980; Rafalowski and Park, 1982; Wrenn et al., 1978). Several methods under investigation included feeding heat-treated soybeans (Mielke and Schingoethe, 1980), cottonseed oil (Steele, 1968), tallow (Pamlquist and Jenkins, 1980), safflower oil (Parry et al., 1963), and whole sunflower seeds (Casper et al., 1988; Middaugh et al., 1988; Rafalowski and Park, 1982). Considerable research has been conducted on feeding protected fat to dairy cows (Edmondson et al., 1974; Mattos and Palmquist, 1974; Scott et al., 1971; Wrenn et al., 1976). A formaldehyde/protein coating protects this fat from hydrogenation by rumen microflora, which allowed fatty acids to be absorbed directly by the small intestine. Feeding rations containing protected fat changed the triglyceride composition of milk fat, while increasing milk production (Bitman et al., 1973; Mattos and Palmquist, 1974; Scott et al., 1971). Protecting fat with formaldehyde has not been approved for use in the U.S. due to transfer of residual formaldehyde to milk (Wrenn et al., 1976). Administration of bovine somatotropin increased milk yield, while having a negligible effect on milk composition (Baer et al., 1989; Eppard et al., 1985a; Kindstedt et al., 1991). Baer et al. (1989) and Eppard et al. (1985a) observed an increase in the unsaturated fatty acid concentration of milk fat when cows received bovine somatotropin. Research has shown that increasing the unsaturated fatty acid concentration of milk fat, butter can be produced that is softer and more spreadable at refrigeration temperatures, while retaining all of the desirable attributes of normal butter (Gerson and Escher, 1966; Harrap, 1973; Middaugh et al., 1988; Wood et al., 1975). Softer butter can be produced by feeding cows protected dietary fat (Buchanan and Rogers, 1973; Kieseker et al., 1974; Wong et al., 1982; Wood et al., 1975), as well as unprotected dietary fat (Middaugh et al., 1988). Residual formaldehyde found in milk and butter is a concern, therefore the use of unprotected fat is the most practical method. The objective of this research was to evaluate the composition, flavor, and physical properties of milk and butter produced from cows being fed unsaturated dietary fat while receiving bovine somatotropin.

Library of Congress Subject Headings

Bovine somatotropin
Dairy cattle -- Feeding and feeds
Milk -- Composition
Unsaturated fatty acids


Includes bibliographical references (pages 33-40)



Number of Pages



South Dakota State University


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