Fatty acid profiles with emphasis on linoleic, linolenic, oleic, and conjugated linoleic acid (CLA) were compared in milk from dairy cows fed diets containing 3.25% supplemental fat and a control diet containing no supplemented fat. The fat was supplied by either whole ground solin, flax, or canola oilseed. Solin (linola) is a new cultivar of flax that contains 28% linoleic acid in the seed, Twelve multiparous Holstein cows were assigned to one of four dietary treatments. The experimental design was a 4 x 4 Latin square with each period consisting of 16 d for adjustment to the diet followed by a 5-d sampling period. Feed intake, milk yield, milk fat yield, and milk fat percentage were not affected by treatment. Adding solin, flax, or canola oilseed to lactation diets produced the highest proportions of linoleic (C18:2), linolenic (C18:3), and oleic (C18:1) acids, respectively, in the lipid fraction of the milk of the cows consuming these diets. The proportions of C6:0 to C16:1 were depressed in the milk fat of cows fed the oilseed diets, compared with the control diet. Increasing the lactation diet levels of C18:2, by using different oilseeds, increased CLA to 1.5% of milk fatty acids. The content of CLA in milk fatty acids, however, did not increase with the solin-supplemented diet compared with the canola-supplemented diet even though the C18:2 level was higher in the former diet.

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Four experiments were conducted with growing chicks to study the effects on performance and fat absorption of feeding rye and wheat diets supplemented with fats of different chain length and degree of saturation. In Experiment 1 it was shown that there was a much greater decrease in feed intake and fat absorption when tallow replaced safflower oil in the diets of chicks fed rye as compared to those fed wheat-based diets. Experiment 2 established the effects on chick performance of supplementing diets based on either rye or wheat with variably saturated fats. Substituting the most saturated triglyceride (C18:0) with the most unsaturated triglyceride (C18:2) in the rye diets improved the respective feed intake, weight gain, and feed conversion efficiency by 11, 75, and 40%, whereas the corresponding changes for the wheat-fed birds were -9, 9, and 16%, respectively. Experiment 3 investigated the effects on chick performance of supplementing rye-based or wheat-based diets with fats of varying chain lengths. Substituting fats containing long chain fatty acids (C18) for those containing shorter chain fatty acids (C12) resulted in respective improvements in weight gain and feed conversion efficiency of 27 and 30% in rye-fed birds and corresponding improvements of only 1 and 9% in the wheat-fed birds. A similar trend also occurred for fat absorption. The results of Experiment 4 demonstrated that older birds (35 versus 6 days of age) fed wheat-based diets absorbed only 1% more fat than younger birds, whereas when rye diets were fed, older birds absorbed 55% more fat than the younger birds. Overall it may be concluded that fat absorption in chicks is affected by chain length and degree of saturation of the fat and the age of the birds and that these factors affect rye-fed birds to a much greater degree than those birds fed wheat-based diets.

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Two experiments were run concurrently to determine the effect of fresh forage consumption on the production and proportions of plasma and milk fat vaccenic acid (VA), conjugated linoleic acid (CLA), and linolenic acid in diary cattle. In experiment 1, the cows consumed 50, 65, and 80% of their feed intake as pasture with the remainder of intake as a barley-based concentrate. The proportion of VA in milk fatty acids increased 12% when pasture intake increased from 50 to 65% of total dry matter intake and VA, CLA, and linolenic acid proportions increased 26, 18, and 27%, respectively, as pasture increased from 65 to 80% of dietary intake. In experiment 2, fresh forage was compared to conserved hay (cut from the same pasture the previous summer) to determine the effect on plasma and milk fat VA, CLA, and linolenic acid. Also, the effect of crushed solin seed (a flax cultivar that is high in linoleic acid) supplementation to the fresh forage diet was determined. Fresh forage compared to conserved hay in the diet, increased the proportion of CLA in the plasma very low density lipoproteins (VLDL) fraction by 71% but had no effect on linolenic acid. Supplementation of the fresh forage diet with a linoleic acid source increased VA and CLA in the plasma VLDL fraction 25 and 58% and slightly decreased the proportion of linolenic acid. Fresh forage, compared to conserved hay, increased milk fat VA and CLA proportions by 22 and 15%. Supplementing the fresh forage diet with linoleic acid from crushed solin seed further increased milk fat VA and CLA proportions 41 and 25%. Solin supplementation in a lactation diet is a superior method to increase CLA levels in milk fat than feeding fresh forage alone.

Menquannr, R. R., WARD For personal use only.

Manquenor, R. R. aNo Weno, A. T. 1979

No abstract