Document Type

Thesis - University Access Only

Award Date

2002

Degree Name

Doctor of Philosophy (PhD)

Department / School

Dairy Science

Abstract

Conjugated linoleic acid (CLA) may decrease the onset and severity of several chronic diseases, including various cancers, atherosclerosis, obesity, bone density loss, and diabetes. These findings are of special interest to the agricultural community because dietary sources of CLA are almost exclusively in beef and dairy products. Dietary factors such as unsaturated oil alter the milk content of CLA because of their effects on the rumen biohydrogenation processes. In the first trial, 12 multiparous Holstein cows were used in a 4 x 4 Latin square with 4 wk periods to determine the effect of fish meal and/or extruded soybeans on milk cis-9, trans-1 ICLA and transvaccenic acid (TVA) concentrations. Treatment diets were 1) control; 2) 0.5 % fish oil from fish meal; 3) 2.5% soybean oil from extruded soybeans; and 4) 0.5% fish oil from fish meal and 2% soybean oil from extruded soybeans. Concentrations of cis-9, trans-1 lCLA in milk fat increased by 0.4, 1.4 and 3.2 fold and TVA concentrations in milk fat increased by 0.4, 1.8 and 3.5 fold for diet 2, 3 and 4 compared with diet 1. Increases in TVA and cis-9, trans-11CLA were 91 to 109% greater when diet 4 was fed than the additive effect of diet 2 and 3. These data indicated that fish meal stimulated conversion of linoleic acid into TV A and/or cis-9, trans-11 CLA. In the second trial, 4 fistulated primiparous cows were used in a 4 X 4 Latin square with 3 wk periods to determine the effect of feeding fish oil, extruded soybeans, or their combination on fatty acid profiles of milk and rumen digesta. Diets consisted of: 1) control diet; 2) a diet with 2% added fat from menhaden fish oil; 3) a diet with 2% added fat from extruded soybeans; and 4) a diet with 1 % added fat from fish oil and I% fat from extruded soybeans. Concentrations of cis-9, trans-11 CLA and TVA in milk fat were increased by 113 and 122%, respectively, with diets 2, 3, and 4 compared with diet 1. Proportions of ruminal cis-9, trans-11 CLA (0.09, 0.26, 0.18, and 0.21 g/l00g fatty acids) and TVA (2.61, 4.56, 4.61, and 4.39 g/l00g fatty acids) increased with all fat supplements. The higher TV A to cis-9, trans-11CLA ratio in the rumen compared with milk indicated that fat supplements increased milk cis-9, trans-11CLA concentration mainly by increasing ruminal production of TV A, which also implied the significant role that mammary delta-9 desaturase plays in milk cis-9, trans-11CLA production. In the third and fourth trials, 12 Holstein cows in experiment 3 and 4 fisulated primiparous Holstein cow in experiment 4 were used in a 4 x 4 Latin square with 4 wk periods to examine the effect of feeding fish oil along with fat sources that varied in their fatty acid profiles on milk, rumen, and plasma cis-9, trans-I I CLA and TVA. Treatment diets were 1) 1 % fish oil+ 2% fat source high in stearic acid (HS); 2) 1 % fish oil+ 2% fat from high oleic acid sunflower seeds (HO); 3) 1 % fish oil+ 2% fat from high linoleic acid sunflower seeds (HLO); and 4) 1 % fish oil+ 2% fat from flax seeds (high linolenic acid; HL). Milk cis-9, trans-11CLA and TV A concentrations were greatest with HLO (1.7, 3.74 g/100 g fatty acids, respectively) and were least with HS (0.7, 1.64 g/100 g fatty acids, respectively). The proportions of ruminal cis-9, trans-11CLA were similar for the HO, HLO, and HLN diets and all were higher than the HS diet. The proportions of ruminal and plasma triglycerides increased with the HO, HLO, and HLN diets compared with the HS diet and the increase was greatest with the HLO diet. The greater TV A to cis-9, trans-11 CLA ratio in the rumen digesta and plasma triglycerides compared with milk fat implied the significant role for the mammary delta-9 desaturase plays in milk cis-9, trans-11CLA production. Our research demonstrated that cis-9, trans-11 CLA concentration in milk fat can be enhanced by the addition of FO along with mono- and polyunsaturated fatty acids to the diet, especially oils high in linoleic acid. The increase in milk cis-9, trans- I I CLA resulted mainly from high ruminal production of TV A that was exclusively incorporated into plasma triglycerides, which also implied the significant role for mammary delta-9 desaturase in milk cis-9, trans-11CLA production.

Library of Congress Subject Headings

Milk Linoleic acid Fatty acids in human nutrition

Format

application/pdf

Number of Pages

159

Publisher

South Dakota State University

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