Abstract
The present study was conducted with four ruminally canulated Holstein cows to observe the effects of monensin or fish oil on diet fermentation and production of conjugated linoleic acids (CLAs) in the rumen when fed diets supplemented with soybean oil and sodium bicarbonate. Cows of the control treatment were fed a basal diet (CON) consisting of 60% commercial concentrate and 40% chopped rye grass hay. Cows of other treatments were fed the same diet as CON, but the concentrate was supplemented with 7% of soybean oil and 0.5% of sodium bicarbonate (SO-B), SO-B supplemented with monensin (30 ppm, SO-BM) or concentrate supplemented with 6.3% of soybean oil, 0.5% of sodium-bicarbonate, 30 ppm of monensin and 0.7% of fish oil (SO-BMF). Dry matter (DM) intake of the cows was significantly (p<0.011) reduced by feeding the SO-BMF diet compared to the other diets which did not differ in DM intake. Whole tract digestibility of major dietary components was significantly (p<0.004-0.027) higher for SO-BMF than the other supplement-containing diets. Dietary supplements did not clearly affect rumen pH and ammonia concentrations compared to the CON diet. Significantly reduced (p<0.05) total VFA concentration was obtained by the addition of fish oil to the diet (SO-BMF) compared to other diets. No differences, however, were obtained in major VFA proportions as well as in total VFA between the supplemented diets. The SO-BM diet increased (p<0.01-0.05) the concentrations of trans-1 C 18:1 and linoleic acid in rumen fluid. Total CLA concentration was also increased by the feeding of SO-B and SO-BM diets during early fermentation times (up to 3 h) post-feeding. Cis-9, trans-11 CLA concentration in rumen fluid was highest (p<0.05) for SO-B up to 1 h while the highest (p<0.01) value for SO-BM occurred at 3 h post-feeding. An increased trans-10, cis-12 CLA concentration was obtained from the SO-B and SO-BM diets at 1 and 3 h post feeding compared to the other diets. Supplementation of oils with monensin and sodium bicarbonate increased (p<0.05) the proportions of C 18:1 and CLA in the plasma of cows, but the effect of monensin and/or fish oil was limited to trans-10, cis-12 CLA.
Highlights
There has been an increasing interest in natural nutrients of ruminant products that have health benefits for humans, and one of them is conjugated linoleic acid (CLA)
The cows were fed the same basal diet as CON cows, but the concentrate was supplemented with 7% of soybean oil and 0.5% of sodiumbicarbonate (SO-B), SO-B diet supplemented with monensin (30 ppm of concentrate, SO-BM) or SO-B diet supplemented with 6.3% soybean oil, 0.5% sodium bicarbonate, 30 ppm monensin and 0.7% fish oil (SO-BMF, Table 1)
The dry matter intake of the cows was significantly (p
Summary
There has been an increasing interest in natural nutrients of ruminant products that have health benefits for humans, and one of them is conjugated linoleic acid (CLA). CLA has Various attempts to increase CLA content in ruminant products have included the application of lipid source. High levels of linoleic and linolenic acids in the form of oil seeds or oils are known to enhance the formation of CLA in the rumen fluid (Wang et al, 2002), milk (Dhiman et al, 2000; Loor et al, 2005) or meat (Choi et al, 2006; Wang et al, 2006). Because the ruminal environment is subject to change by dietary manipulation it is possible that changes in pH of rumen fluid will have an effect on CLA formation
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