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|Autori: ||La Terra, Stefania|
|Titolo: ||The influence of native pasture on conjugated linoleic acid and lipophilic antioxidants content in cows' plasma and milk|
|Abstract: ||CLA and antioxidants are important for the human nutrition. Many human diseases, such as cancer, artherosclerosis and diabetes have been related to low ingestion in the diet. Dairy products represent the nutrients which are richest in CLA.
Milk Antioxidants are less important for human nutrition. However, antioxidants are essential for milk stability because they are able to prevent milk oxidation.
It has been widely reported that a considerable amount of variation in CLA and antioxidant content of milk fat exists. This variation can be attributed to several factors such as: animal diet composition, management systems, animal species, breed, stage of lactation and age of animals.
For example, green forage relative to conserved forage feeding increased CLA and antioxidant in milk. Geographical locations, as well as plant species have been related to the same parameters.
It has also been demonstrated that sheep and goats have less beta carotene in the milk compared to cows. These differences of might be explained, at least in part, by different absorption of beta carotene from the intestine. Other authors have shown, that there are differences between Brown Swiss, Holstein-Friesian, and Jersey breeds with respect to the activity of the mammary enzyme stearoyl Co-A desaturase. This enzyme oxidizes C16:0 and C18:0 to C16:1 and C18:1 and is involved in CLA production. Milk fat content and in consequence, also CLA and antioxidants contents might be related to stage of lactation.
In another study, older cows (>7 lactations) had higher CLA in milk than younger cows (1 to 3 lactations). Age differences in milk fat CLA content were attributed to differences in desaturase enzyme activities and/or fatty acid metabolism and synthesis between older and younger cattle.
Dairy production plays an important role for Sicilian economics. Bovine farming is mainly located in Palermo and in Ragusa, while caprine farming are situated in Agrigento Messina and Caltanissetta.
In regard of the present research studies, it has been decided to focus on the effects of pasture feeding and animal species on contents of CLA and antioxidants in milk. Two major studies have been performed.
The first study dealt with different levels of pasture intake in the diet.
Total CLA, PUFA and antioxidants in plasma and bovine milk were studied in three groups of cows. One group fed TMR (no pasture); the second group fed TMR supplemented with 30% DM of pasture, and the last group fed TMR supplemented with 70% DM of pasture.
Cattle breed, lactation days and milk production level were similar for all the 3 groups of cows. Blood from the jugular vein and milk samples were collected at the same time during the afternoon milking. Samples were transported to the laboratory and stored at minus 80 degrees Celsius. The experiment was repeated three times. The effect of pasture in the diet was significant (P<0.01) for CLA concentration in plasma.
The second study treated the effects of different animal species and bovine races on alfa and gamma tocopherol content in milk in absence of pasture. Milk samples from different species (buffalo, cow, goat and sheep) have been collected between June and July from five farmhouses located on hyblean highlands of South- eastern Sicily.
In the present investigation the discrepancies found about the levels of a-tocopherol in our milk samples could be explained with interspecies variability and the similarity could be the consequence of a combination of feed characteristics. Although a-tocopherol content was within the range reported in literature, the low concentrations might be explained by poor pasture in a- tocopherol in summer and by vitamin decrease in animal's plasma and in milk in answer to a major heat stress.
However, ewes' milk had higher significantly levels and buffalo's milk lower (p<0.05) of a-tocopherol than other milk varieties. We cannot compare our results about g-tocopherol content in milks because lacking data in literature, although its beneficial roles in human health and in protecting foods. However, in our study differences species-specific have been found with a higher significantly content (P <0.05) of g isomer in goat and buffalo milk compared to other milk varieties.|
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