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| Author(s): |
Juliana Jorge Paschoal
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Pirassununga. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Zootecnica e Engenharia de Alimentos (FZE/BT) |
| Defense date: | 2007-04-20 |
| Examining board members: |
Marcus Antônio Zanetti;
Mariza Pires de Melo;
Francisco Palma Rennó;
Márcia Saladini Vieira Salles;
Edison Schalch
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| Advisor: | Marcus Antônio Zanetti |
| Abstract | |
The manipulation of ruminant diet can modify the fatty acid profiles increasing its nutritive and therapeutic value. However, this change in fatty acid composition can increase milk oxidation and can affect its flavor and shelf life. The objective of this study was to evaluate the effect of extruded soybean diet and organic selenium supplementation on milk composition, CLA content, fatty acid profiles and oxidative stability of milk. Twenty four Holstein cows were grouped into three blocks according to number of parturition and were fed diets containing 56% forage and 44% concentrate. The animals were allocated to three treatments: A) control diet, B) 21% extruded soybean diet and C) 21% extruded soybean diet + 5 mg of organic selenium. The diets were formulated to provide the same energy and protein levels. The extruded soybean did not affect the dry matter intake, body weight and milk production. The cows fed extruded soybean diet produced milk with lower (P<0,01) concentration of fat, lower (P<0,01) concentration of short and medium chain fatty acids and higher (P<0,01) concentration of long chain fatty acids when compared to control group. Regarding to saturation level, those animals produced milk with lower (P<0,01) concentration of saturated fatty acids and higher (P<0,01) concentration of polyunsaturated fatty acids and CLA content. The serum concentration of cholesterol was higher (P<0,01) for treatments containing extruded soybean when compared to control. The organic selenium supplementation increased (P<0,05) milk selenium concentration and delayed milk oxidation measured by peroxide value (P<0,01). The inclusion of 21% of extruded soybean in dairy cattle diet resulted in production of milk fat with modified fatty acid profile with lower concentration of saturated fatty acids and higher concentration of polyunsaturated fatty acids and CLA content. However the milk fat was more susceptible to oxidation. The organic selenium supplementation was efficient to overcome this problem and therefore could maintain the stability of milk. (AU) | |